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Archive for the ‘Behavioral Genetics’ Category


Genetic link to sleep and mood disorders

Larry H. Bernstein, MD, FCAP, Curator

LPBI

 

Scientists identify molecular link between sleep and mood

A poor night’s sleep is enough to put anyone in a bad mood, and although scientists have long suspected a link between mood and sleep, the molecular basis of this connection remained a mystery. Now, new research has found several rare genetic mutations on the same gene that definitively connect the two.

Sleep goes hand-in-hand with mood. People suffering from depression and mania, for example, frequently have altered sleeping patterns, as do those with seasonal affective disorder (SAD). And although no one knows exactly how these changes come about, in SAD sufferers they are influenced by changes in light exposure, the brain’s time-keeping cue. But is mood affecting sleep, is sleep affecting mood, or is there a third factor influencing both? Although a number of tantalizing leads have linked the circadian clock to mood, there is “no definitive factor that proves causality or indicates the direction of the relationship,” says Michael McCarthy, a neurobiologist at the San Diego Veterans’ Affairs Medical Center and the University of California (UC), San Diego.

To see whether they could establish a link between the circadian clock, sleep, and mood, scientists in the new study looked at the genetics of a family that suffers from abnormal sleep patterns and mood disorders, including SAD and something called advanced sleep phase, a condition in which people wake earlier and sleep earlier than normal. The scientists screened the family for mutations in key genes involved in the circadian clock, and identified two rare variants of the PERIOD3 (PER3) gene in members suffering from SAD and advanced sleep phase. “We found a genetic change in people who have both seasonal affective disorder and the morning lark trait” says lead researcher Ying-Hui Fu, a neuroscientist at UC San Francisco. When the team tested for these mutations in DNA samples from the general population, they found that they were extremely rare, appearing in less than 1% of samples.

Fu and her team then created mice that carried the novel genetic variants. These transgenic mice showed an unusual sleep-wake cycle and struggled less when handled by the researchers, a typical sign of depression. They also had lower levels of PER2, a protein involved in circadian rhythms, than unmutated mice, providing a possible molecular explanation for the unusual sleep patterns in the family. Fu says this supports the link between the PER3 mutations and both sleep and mood. “PER3’s role in mood regulation has never been demonstrated directly before,” she says. “Our results indicate that PER3 might function in helping us adjust to seasonal changes,” by modifying the body’s internal clock.

To investigate further, the team studied mice lacking a functional PER3 gene. They found that these mice showed symptoms of SAD, exhibiting more severe depression when the duration of simulated daylight in the laboratory was reduced. Because SAD affects between 2% and 9% of people worldwide, the novel variants can’t explain it fully. But understanding the function of PER3 could yield insights into the molecular basis of a wide range of sleep and mood disorders, Fu says.

Together, these experiments show that the PERIOD3 gene likely plays a key role in regulating the sleep-wake cycle, influencing mood and regulating the relationship between depression and seasonal changes in light availability, the team reports today in the Proceedings of the National Academy of Sciences. “The identification of a mutation in PER3 with such a strong effect on mood is remarkable,” McCarthy says. “It suggests an important role for the circadian clock in determining mood.”

The next step will be to investigate how well these results generalize to other people suffering from mood and sleep disorders. “It will be interesting to see if other rare variants in PER3 are found, or if SAD is consistently observed in other carriers,” McCarthy says. That could eventually lead to new drugs that selectively target the gene, which McCarthy says, “could be a strategy for treating mood or sleep disorders.”

 

http://dx.doi.org:/10.1126/science.aaf4095

 

 

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Sleep apnea insular glutamate and GABA levels

Larry H. Bernstein, MD, FCAP, Curator

LPBI

 

Sleep Apnea Takes a Toll on Brain Function

UCLA   http://www.biosciencetechnology.com/news/2016/02/sleep-apnea-takes-toll-brain-function

 

One in 15 adults has moderate to severe obstructive sleep apnea, a disorder in which a person’s breathing is frequently interrupted during sleep — as many as 30 times per hour.

People with sleep apnea also often report problems with thinking such as poor concentration, difficulty with memory and decision-making, depression, and stress.

According to new research from the UCLA School of Nursing,  published online in the Journal of Sleep Research,  people with sleep apnea show significant changes in the levels of two important brain chemicals, which could be a reason that many have symptoms that impact their day-to-day lives.

UCLA researchers looked at levels of these neurotransmitters — glutamate and gamma-aminobutyric acid, known as GABA — in a brain region called the insula, which integrates signals from higher brain regions to regulate emotion, thinking and physical functions such as blood pressure and perspiration. They found that people with sleep apnea had decreased levels of GABA and unusually high levels of glutamate.

GABA is a chemical messenger that acts as an inhibitor in the brain, which can slow things down and help to keep people calm — like a brake pedal. GABA affects mood and helps make endorphins.

Glutamate, by contrast, is like an accelerator; when glutamate levels are high, the brain is working in a state of stress, and consequently doesn’t function as effectively. High levels of glutamate can also be toxic to nerves and neurons.

“In previous studies, we’ve seen structural changes in the brain due to sleep apnea, but in this study we actually found substantial differences in these two chemicals that influence how the brain is working,” said Paul Macey, the lead researcher on the study and an associate professor at the UCLA School of Nursing.

Macey said the researchers were taken aback by the differences in the GABA and glutamate levels.

“It is rare to have this size of difference in biological measures,” Macey said. “We expected an increase in the glutamate, because it is a chemical that causes damage in high doses and we have already seen brain damage from sleep apnea. What we were surprised to see was the drop in GABA. That made us realize that there must be a reorganization of how the brain is working.”

Macey said the study’s results are, in a way, encouraging. “In contrast with damage, if something is working differently, we can potentially fix it.”

The link between sleep apnea and changes in the state of the brain is important news for clinicians, Macey said.

“What comes with sleep apnea are these changes in the brain, so in addition to prescribing continuous positive airway pressure, or CPAP — a machine used to help an individual sleep easier, which is the gold standard treatment for sleep disturbance — physicians now know to pay attention to helping their patients who have these other symptoms,” Macey said. “Stress, concentration, memory loss — these are the things people want fixed.”

In future studies, the researchers hope to determine whether treating the sleep apnea — using CPAP or other methods — returns patients’ brain chemicals back to normal levels. If not, they will turn to the question of what treatments could be more effective. They are also studying the impacts of mindfulness exercises to see if they can reduce glutamate levels by calming the brain.

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Mindful Discoveries

Larry H. Bernstein, MD, FCAP, Curator

LPBI

 

Schizophrenia and the Synapse

Genetic evidence suggests that overactive synaptic pruning drives development of schizophrenia.

By Ruth Williams | January 27, 2016 … more follows)

http://www.the-scientist.com/?articles.view/articleNo/45189/title/Schizophrenia-and-the-Synapse/

http://www.the-scientist.com/images/News/January2016/Schizophrenia.jpg

C4 (green) at synapses of human neurons

Compared to the brains of healthy individuals, those of people with schizophrenia have higher expression of a gene called C4, according to a paper published inNature today (January 27). The gene encodes an immune protein that moonlights in the brain as an eradicator of unwanted neural connections (synapses). The findings, which suggest increased synaptic pruning is a feature of the disease, are a direct extension of genome-wide association studies (GWASs) that pointed to the major histocompatibility (MHC) locus as a key region associated with schizophrenia risk.

“The MHC [locus] is the first and the strongest genetic association for schizophrenia, but many people have said this finding is not useful,” said psychiatric geneticist Patrick Sullivan of the University of North Carolina School of Medicine who was not involved in the study. “The value of [the present study is] to show that not only is it useful, but it opens up new and extremely interesting ideas about the biology and therapeutics of schizophrenia.”

Schizophrenia has a strong genetic component—it runs in families—yet, because of the complex nature of the condition, no specific genes or mutations have been identified. The pathological processes driving the disease remain a mystery.

Researchers have turned to GWASs in the hope of finding specific genetic variations associated with schizophrenia, but even these have not provided clear candidates.

“There are some instances where genome-wide association will literally hit one base [in the DNA],” explained Sullivan. While a 2014 schizophrenia GWAS highlighted the MHC locus on chromosome 6 as a strong risk area, the association spanned hundreds of possible genes and did not reveal specific nucleotide changes. In short, any hope of pinpointing the MHC association was going to be “really challenging,” said geneticist Steve McCarroll of Harvard who led the new study.

Nevertheless, McCarroll and colleagues zeroed in on the particular region of the MHC with the highest GWAS score—the C4 gene—and set about examining how the area’s structural architecture varied in patients and healthy people.

The C4gene can exist in multiple copies (from one to four) on each copy of chromosome 6, and has four different forms: C4A-short, C4B-short, C4A-long, and C4B-long. The researchers first examined the “structural alleles” of the C4 locus—that is, the combinations and copy numbers of the different C4 forms—in healthy individuals. They then examined how these structural alleles related to expression of both C4Aand C4B messenger RNAs (mRNAs) in postmortem brain tissues.From this the researchers had a clear picture of how the architecture of the C4 locus affected expression ofC4A and C4B. Next, they compared DNA from roughly 30,000 schizophrenia patients with that from 35,000 healthy controls, and a correlation emerged: the alleles most strongly associated with schizophrenia were also those that were associated with the highest C4A expression. Measuring C4A mRNA levels in the brains of 35 schizophrenia patients and 70 controls then revealed that, on average, C4A levels in the patients’ brains were 1.4-fold higher.C4 is an immune system “complement” factor—a small secreted protein that assists immune cells in the targeting and removal of pathogens. The discovery of C4’s association to schizophrenia, said McCarroll, “would have seemed random and puzzling if it wasn’t for work . . . showing that other complement components regulate brain wiring.” Indeed, complement protein C3 locates at synapses that are going to be eliminated in the brain, explained McCarroll, “and C4 was known to interact with C3 . . . so we thought well, actually, this might make sense.”McCarroll’s team went on to perform studies in mice that revealed C4 is necessary for C3 to be deposited at synapses. They also showed that the more copies of the C4 gene present in a mouse, the more the animal’s neurons were pruned.Synaptic pruning is a normal part of development and is thought to reflect the process of learning, where the brain strengthens some connections and eradicates others. Interestingly, the brains of deceased schizophrenia patients exhibit reduced neuron density. The new results, therefore, “make a lot of sense,” said Cardiff University’s Andrew Pocklington who did not participate in the work. They also make sense “in terms of the time period when synaptic pruning is occurring, which sort of overlaps with the period of onset for schizophrenia: around adolescence and early adulthood,” he added.

“[C4] has not been on anybody’s radar for having anything to do with schizophrenia, and now it is and there’s a whole bunch of really neat stuff that could happen,” said Sullivan. For one, he suggested, “this molecule could be something that is amenable to therapeutics.”

A. Sekar et al., “Schizophrenia risk from complexvariation of complement component 4,”Nature,   http://dx.doi.com:/10.1038/nature16549, 2016.     

Tags schizophrenia, neuroscience, gwas, genetics & genomics, disease/medicine and cell & molecular biology

 

Schizophrenia: From genetics to physiology at last

Ryan S. Dhindsa& David B. Goldstein

Nature (2016)  http://dx.doi.org://10.1038/nature16874

The identification of a set of genetic variations that are strongly associated with the risk of developing schizophrenia provides insights into the neurobiology of this destructive disease.

http://www.nytimes.com/2016/01/28/health/schizophrenia-cause-synaptic-pruning-brain-psychiatry.html

 

Genetic study provides first-ever insight into biological origin of schizophrenia

Suspect gene may trigger runaway synaptic pruning during adolescence — NIH-funded study

NIH/NATIONAL INSTITUTE OF MENTAL HEALTH

IMAGE

http://media.eurekalert.org/multimedia_prod/pub/web/107629_web.jpg

The site in Chromosome 6 harboring the gene C4 towers far above other risk-associated areas on schizophrenia’s genomic “skyline,” marking its strongest known genetic influence. The new study is the first to explain how specific gene versions work biologically to confer schizophrenia risk.  CREDIT  Psychiatric Genomics Consortium

Versions of a gene linked to schizophrenia may trigger runaway pruning of the teenage brain’s still-maturing communications infrastructure, NIH-funded researchers have discovered. People with the illness show fewer such connections between neurons, or synapses. The gene switched on more in people with the suspect versions, who faced a higher risk of developing the disorder, characterized by hallucinations, delusions and impaired thinking and emotions.

“Normally, pruning gets rid of excess connections we no longer need, streamlining our brain for optimal performance, but too much pruning can impair mental function,” explained Thomas Lehner, Ph.D., director of the Office of Genomics Research Coordination of the NIH’s National Institute of Mental Health (NIMH), which co-funded the study along with the Stanley Center for Psychiatric Research at the Broad Institute and other NIH components. “It could help explain schizophrenia’s delayed age-of-onset of symptoms in late adolescence/early adulthood and shrinkage of the brain’s working tissue. Interventions that put the brakes on this pruning process-gone-awry could prove transformative.”

The gene, called C4 (complement component 4), sits in by far the tallest tower on schizophrenia’s genomic “skyline” (see graph below) of more than 100 chromosomal sites harboring known genetic risk for the disorder. Affecting about 1 percent of the population, schizophrenia is known to be as much as 90 percent heritable, yet discovering how specific genes work to confer risk has proven elusive, until now.

A team of scientists led by Steve McCarroll, Ph.D., of the Broad Institute and Harvard Medical School, Boston, leveraged the statistical power conferred by analyzing the genomes of 65,000 people, 700 postmortem brains, and the precision of mouse genetic engineering to discover the secrets of schizophrenia’s strongest known genetic risk. C4’s role represents the most compelling evidence, to date, linking specific gene versions to a biological process that could cause at least some cases of the illness.

“Since schizophrenia was first described over a century ago, its underlying biology has been a black box, in part because it has been virtually impossible to model the disorder in cells or animals,” said McCarroll. “The human genome is providing a powerful new way in to this disease. Understanding these genetic effects on risk is a way of prying open that block box, peering inside and starting to see actual biological mechanisms.”

McCarroll’s team, including Harvard colleagues Beth Stevens, Ph.D., Michael Carroll, Ph.D., and Aswin Sekar, report on their findings online Jan. 27, 2016 in the journal Nature.

A swath of chromosome 6 encompassing several genes known to be involved in immune function emerged as the strongest signal associated with schizophrenia risk in genome-wide analyses by the NIMH-funded Psychiatric Genomics Consortium over the past several years. Yet conventional genetics failed to turn up any specific gene versions there linked to schizophrenia.

To discover how the immune-related site confers risk for the mental disorder, McCarroll’s team mounted a search for “cryptic genetic influences” that might generate “unconventional signals.” C4, a gene with known roles in immunity, emerged as a prime suspect because it is unusually variable across individuals. It is not unusual for people to have different numbers of copies of the gene and distinct DNA sequences that result in the gene working differently.

The researchers dug deeply into the complexities of how such structural variation relates to the gene’s level of expression and how that, in turn, might relate to schizophrenia. They discovered structurally distinct versions that affect expression of two main forms of the gene in the brain. The more a version resulted in expression of one of the forms, called C4A, the more it was associated with schizophrenia. The more a person had the suspect versions, the more C4 switched on and the higher their risk of developing schizophrenia. Moreover, in the human brain, the C4 protein turned out to be most prevalent in the cellular machinery that supports connections between neurons.

Adapting mouse molecular genetics techniques for studying synaptic pruning and C4’s role in immune function, the researchers also discovered a previously unknown role for C4 in brain development. During critical periods of postnatal brain maturation, C4 tags a synapse for pruning by depositing a sister protein in it called C3. Again, the more C4 got switched on, the more synapses got eliminated.

In humans, such streamlining/pruning occurs as the brain develops to full maturity in the late teens/early adulthood – conspicuously corresponding to the age-of-onset of schizophrenia symptoms.

Future treatments designed to suppress excessive levels of pruning by counteracting runaway C4 in at risk individuals might nip in the bud a process that could otherwise develop into psychotic illness, suggest the researchers. And thanks to the head start gained in understanding the role of such complement proteins in immune function, such agents are already in development, they note.

“This study marks a crucial turning point in the fight against mental illness. It changes the game,” added acting NIMH director Bruce Cuthbert, Ph.D. “Thanks to this genetic breakthrough, we can finally see the potential for clinical tests, early detection, new treatments and even prevention.”

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VIDEO: Opening Schizophrenia’s Black Box https://youtu.be/s0y4equOTLg

Reference: Sekar A, Biala AR, de Rivera H, Davis A, Hammond TR, Kamitaki N, Tooley K Presumey J Baum M, Van Doren V, Genovese G, Rose SA, Handsaker RE, Schizophrenia Working Group of the Psychiatric Genomics Consortium, Daly MJ, Carroll MC, Stevens B, McCarroll SA. Schizophrenia risk from complex variation of complement component 4.Nature. Jan 27, 2016. DOI: 10.1038/nature16549.

 

Schizophrenia risk from complex variation of complement component 4

Aswin SekarAllison R. BialasHeather de RiveraAvery DavisTimothy R. Hammond, …., Michael C. CarrollBeth Stevens Steven A. McCarroll

Nature(2016)   http://dx.doi.org:/10.1038/nature16549

Schizophrenia is a heritable brain illness with unknown pathogenic mechanisms. Schizophrenia’s strongest genetic association at a population level involves variation in the major histocompatibility complex (MHC) locus, but the genes and molecular mechanisms accounting for this have been challenging to identify. Here we show that this association arises in part from many structurally diverse alleles of the complement component 4 (C4) genes. We found that these alleles generated widely varying levels of C4A and C4B expression in the brain, with each common C4 allele associating with schizophrenia in proportion to its tendency to generate greater expression of C4A. Human C4 protein localized to neuronal synapses, dendrites, axons, and cell bodies. In mice, C4 mediated synapse elimination during postnatal development. These results implicate excessive complement activity in the development of schizophrenia and may help explain the reduced numbers of synapses in the brains of individuals with schizophrenia.

Figure 1: Structural variation of the complement component 4 (C4) gene.

http://www.nature.com/nature/journal/vaop/ncurrent/carousel/nature16549-f1.jpg

a, Location of the C4 genes within the major histocompatibility complex (MHC) locus on human chromosome 6. b, Human C4 exists as two paralogous genes (isotypes), C4A and C4B; the encoded proteins are distinguished at a key site

http://www.nature.com/nature/journal/vaop/ncurrent/carousel/nature16549-f3.jpg

http://www.nature.com/nature/journal/vaop/ncurrent/carousel/nature16549-sf8.jpg

Gene Study Points Toward Therapies for Common Brain Disorders

University of Edinburgh    http://www.dddmag.com/news/2016/01/gene-study-points-toward-therapies-common-brain-disorders

Scientists have pinpointed the cells that are likely to trigger common brain disorders, including Alzheimer’s disease, Multiple Sclerosis and intellectual disabilities.

It is the first time researchers have been able to identify the particular cell types that malfunction in a wide range of brain diseases.

Scientists say the findings offer a roadmap for the development of new therapies to target the conditions.

The researchers from the University of Edinburgh’s Centre for Clinical Brain Sciences used advanced gene analysis techniques to investigate which genes were switched on in specific types of brain cells.

They then compared this information with genes that are known to be linked to each of the most common brain conditions — Alzheimer’s disease, anxiety disorders, autism, intellectual disability, multiple sclerosis, schizophrenia and epilepsy.

Their findings reveal that for some conditions, the support cells rather than the neurons that transmit messages in the brain are most likely to be the first affected.

Alzheimer’s disease, for example, is characterised by damage to the neurons. Previous efforts to treat the condition have focused on trying to repair this damage.

The study found that a different cell type — called microglial cells — are responsible for triggering Alzheimer’s and that damage to the neurons is a secondary symptom of disease progression.

Researchers say that developing medicines that target microglial cells could offer hope for treating the illness.

The approach could also be used to find new treatment targets for other diseases that have a genetic basis, the researchers say.

Dr Nathan Skene, who carried out the study with Professor Seth Grant, said: “The brain is the most complex organ made up from a tangle of many cell types and sorting out which of these cells go wrong in disease is of critical importance to developing new medicines.”

Professor Seth Grant said: “We are in the midst of scientific revolution where advanced molecular methods are disentangling the Gordian Knot of the brain and completely unexpected new pathways to solving diseases are emerging. There is a pressing need to exploit the remarkable insights from the study.”

 

Quantitative multimodal multiparametric imaging in Alzheimer’s disease

Qian Zhao, Xueqi Chen, Yun Zhou      Brain Informatics  http://link.springer.com/article/10.1007/s40708-015-0028-9

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder, causing changes in memory, thinking, and other dysfunction of brain functions. More and more people are suffering from the disease. Early neuroimaging techniques of AD are needed to develop. This review provides a preliminary summary of the various neuroimaging techniques that have been explored for in vivo imaging of AD. Recent advances in magnetic resonance (MR) techniques, such as functional MR imaging (fMRI) and diffusion MRI, give opportunities to display not only anatomy and atrophy of the medial temporal lobe, but also at microstructural alterations or perfusion disturbance within the AD lesions. Positron emission tomography (PET) imaging has become the subject of intense research for the diagnosis and facilitation of drug development of AD in both animal models and human trials due to its non-invasive and translational characteristic. Fluorodeoxyglucose (FDG) PET and amyloid PET are applied in clinics and research departments. Amyloid beta (Aβ) imaging using PET has been recognized as one of the most important methods for the early diagnosis of AD, and numerous candidate compounds have been tested for Aβ imaging. Besides in vivo imaging method, a lot of ex vivo modalities are being used in the AD researches. Multiphoton laser scanning microscopy, neuroimaging of metals, and several metal bioimaging methods are also mentioned here. More and more multimodality and multiparametric neuroimaging techniques should improve our understanding of brain function and open new insights into the pathophysiology of AD. We expect exciting results will emerge from new neuroimaging applications that will provide scientific and medical benefits.

Keywords –   Alzheimer’s disease Neuroimaging PET MRI Amyloid beta Multimodal

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that gradually destroys brain cells, causing changes in memory, thinking, and other dysfunction of brain functions [1]. AD is considered to a prolonged preclinical stage where neuropathological changes precede the clinical symptoms [2]. An estimation of 35 million people worldwide is living with this disease. If effective treatments are not discovered in a timely fashion, the number of AD cases is anticipated to rise to 113 million by 2050 [3].

Amyloid beta (Aβ) and tau are two of the major biomarkers of AD, and have important and different roles in association with the progression of AD pathophysiology. Jack et al. established hypothetical models of the major biomarkers of AD. By renewing and modifying the models, they found that the two major proteinopathies underlying AD biomarker changes, Aβ and tau, may be initiated independently in late onset AD where they hypothesize that an incident Aβ pathophysiology can accelerate an antecedent limbic and brainstem tauopathy [4]. MRI technique was used in the article, which revealed that the level of Aβ load was associated with a shorter time-to-progression of AD [5]. This warrants an urgent need to develop early neuroimaging techniques of AD neuropathology that can detect and predict the disease before the onset of dementia, monitor therapeutic efficacy in halting and slowing down progression in the earlier stage of the disease.

There have been various reports on the imaging assessments of AD. Some measurements reflect the pathology of AD directly, including positron emission tomography (PET) amyloid imaging and cerebrospinal fluid (CSF) beta-amyloid 42 (Aβ42), while others reflect neuronal injury associated with AD indirectly, including CSF tau (total and phosphorylated tau), fluorodeoxy-d-glucose (FDG)-PET, and MRI. AD Neuroimaging Initiative (ADNI) has been to establish the optimal panel of clinical assessments, MRI and PET imaging measures, as well as other biomarkers from blood and CSF, to inform clinical trial design for AD therapeutic development. At the same time, it has been highly productive in generating a wealth of data for elucidating disease mechanisms occurring during early stages of preclinical and prodromal AD [6].

Single neuroimaging often reflects limit information of AD. As a result, multimodal neuroimaging is widely used in neuroscience researches, as it overcomes the limitations of individual modalities. Multimodal multiparametric imaging mean the combination of different imaging techniques, such as PET, MRI, simultaneously or separately. The multimodal multiparametric imaging enables the visualization and quantitative analysis of the alterations in brain structure and function, such as PET/CT, and PET/MRI. [7]. In this review article, we summarize and discuss the main applications, findings, perspectives as well as advantages and challenges of different neuroimaging in AD, especially MRI and PET imaging.

2 Magnetic resonance imaging

MRI demonstrates specific volume loss or cortical atrophy patterns with disease progression in AD patients [810]. There are several MRI techniques and analysis methods used in clinical and scientific research of AD. Recent advances in MR techniques, such as functional MRI (fMRI) and diffusion MRI, depict not only anatomy and atrophy of the medial temporal lobe (MTL), but also microstructural alterations or perfusion disturbance within this region.

2.1 Functional MRI

Because of the cognitive reserve (CR), the relationship between severity of AD patients’ brain damage and corresponding clinical symptoms is not always paralleled [11, 12]. Recently, resting-state fMRI (RS-fMRI) is popular for its ability to map brain functional connectivity non-invasively [13]. By using RS-fMRI, Bozzali et al. reported that the CR played a role in modulating the effect of AD pathology on default mode network functional connectivity, which account for the variable clinical symptoms of AD [14]. Moreover, AD patients with higher educated experience were able to recruit compensatory neural mechanisms, which can be measured using RS-fMRI. Arterial spin-labeled (ASL) MRI is another functional brain imaging modality, which measures cerebral blood flow (CBF) by magnetically labeled arterial blood water following through the carotid and vertebral arteries as an endogenous contrast medium. Several studies have concluded the characteristics of CBF changes in AD patients using ASL-MRI [1517].

At some point in time, sufficient brain damage accumulates to result in cognitive symptoms and impairment. Mild cognitive impairment (MCI) is a condition in which subjects are usually only mildly impaired in memory with relative preservation of other cognitive domains and functional activities and do not meet the criteria for dementia [18], or as the prodromal state AD [19]. MCI patients are at a higher risk of developing AD and up to 15 % convert to AD per year [18]. Binnewijzend et al. have reported the pseudocontinuous ASL could distinguish both MCI and AD from healthy controls, and be used in the early diagnosis of AD [20]. In their continuous study, they used quantitative whole brain pseudocontinuous ASL to compare regional CBF (rCBF) distribution patterns in different types of dementia, and concluded that ASL-MRI could be a non-invasive and easily accessible alternative to FDG-PET imaging in the assessment of CBF of AD patients [21].

2.2 Structure MRI

Structural MRI (sMRI) has already been a reliable imaging method in the clinical diagnosis of AD, characterized as gray matter reduction and ventricular enlargement in standard T1-weighted sequences [9]. Locus coeruleus (LC) and substantia nigra (SN) degeneration was seen in AD. By using new quantitative calculating method, Chen et al. presented a new quantitative neuromelanin MRI approach for simultaneous measurement of locus LC and SN of brainstem in living human subjects [22]. The approach they used demonstrated advantages in image acquisition, pre-processing, and quantitative analysis. Numerous transgenic animal models of amyloidosis are available, which can manipulate a lot of neuropathological features of AD progression from the deposition of β-amyloid [23]. Braakman et al. demonstrated the dynamics of amyloid plaque formation and development in a serial MRI study in a transgenic mouse model [24]. Increased iron accumulation in gray matter is frequently observed in AD. Because of the paramagnetic nature of iron, MRI shows nice potential in the investigating iron levels in AD [25]. Quantitative MRI was shown high sensitivity and specificity in mapping cerebral iron deposition, and helped in the research on AD diagnosis [26].

The imaging patterns are always associated with the pathologic changes, such as specific protein markers. Spencer et al. manifested the relationship between quantitative T1 and T2 relaxation time changes and three immunohistochemical markers: β-amyloid, neuron-specific nuclear protein (a marker of neuronal cell load), and myelin basic protein (a marker of myelin load) in AD transgenic mice [27].

High-field MRI has been successfully applied to imaging plaques in transgenic mice for over a decade without contrast agents [24, 2830]. Sillerud et al. devised a method using blood–brain barrier penetrating, amyloid-targeted, superparamagnetic iron oxide nanoparticles (SPIONs) for better imaging of amyloid plaque [31]. Then, they successfully used this SPION-MRI to assess the drug efficacy on the 3D distribution of Aβ plaques in transgenic AD mouse [32].

2.3 Diffusion MRI

Diffusion-weighted imaging (DWI) is a sensitive tool that allows quantifying of physiologic alterations in water diffusion, which result from microscopic structural changes.

Diffusion tensor imaging (DTI) is a well-established and commonly employed diffusion MRI technique in clinical and research on neuroimaging studies, which is based on a Gaussian model of diffusion processes [33]. In general, AD is associated with widespread reduced fractional anisotropy (FA) and increased mean diffusivity (MD) in several regions, most prominently in the frontal and temporal lobes, and along the cingulum, corpus callosum, uncinate fasciculus, superior longitudinal fasciculus, and MTL-associated tracts than healthy controls [3437]. Acosta-Cabronero et al. reported increased axial diffusivity and MD in the splenium, which were the earliest abnormalities in AD [38]. FA and radial diffusivity (DR) differences in the corpus callosum, cingulum, and fornix were found to separate individuals with MCI who converted to AD from non-converters [39]. DTI was also found to be a better predictor of AD-specific MTL atrophy when compared to CSF biomarkers [40]. These findings suggested the potential clinical utility of DTI as early biomarkers of AD and its progression. However, an increase in MD and DR and a decrease in FA with advancing age in selective brain regions have been previously reported [41, 42]. Diffusion MRI can be also used in the classifying of various stages of AD. Multimodal classification method, which combined fMRI and DTI, separated more MCI from healthy controls than single approaches [43].

In recent years, tau has emerged as a potential target for therapeutic intervention. Tau plays a critical role in the neurodegenerative process forming neurofibrillary tangles, which is a major hallmark of AD and correlates with clinical disease progression. Wells et al. applied multiparametric MRI, containing high-resolution structure MRI (sMRI), a novel chemical exchange saturation transfer (CEST) MRI, DTI, and ASL, and glucose CEST to measure changes of tau pathology in AD transgenic mouse [44].

Besides DWI MRI, perfusion-weighted imaging (PWI) is another advanced MR technique, which could measure the cerebral hemodynamics at the capillary level. Zimny et al. evaluated the correlation of MTL with both DWI and PWI in AD and MCI patients [45].

3 Positron emission tomography

PET is a specific imaging technique applying in researches of brain function and neurochemistry of small animals, medium-sized animals, and human subjects [4648]. As a particular brain imaging technique, PET imaging has become the subject of intense research for the diagnosis and facilitation of drug development of AD in both animal models and human trials due to its non-invasive and translational characteristic. PET with various radiotracers is considered as a standard non-invasive quantitative imaging technique to measure CBF, glucose metabolism, and β-amyloid and tau deposition.

3.1 FDG-PET

To date, 18F-FDG is one of the best and widely used neuroimaging tracers of PET, which employed for research and clinical assessment of AD [49]. Typical lower FDG metabolism was shown in the precuneus, posterior cingulate, and temporal and parietal cortex with progression to whole brain reductions with increasing disease progress in AD brains [50, 51]. FDG-PET imaging reflects the cerebral glucose metabolism, neuronal injury, which provides indirect evidence on cognitive function and progression that cannot be provided by amyloid PET imaging.

Schraml et al. [52] identified a significant association between hypometabolic convergence index and phenotypes using ADNI data. Some researchers also used 18F-FDG-PET to analyze genetic information with multiple biomarkers to classify AD status, predicting cognitive decline or MCI to AD conversion [5355]. Trzepacz et al. [56] reported multimodal AD neuroimaging study, using MRI, 11C-PiB PET, and 18F-FDG-PET imaging to predict MCI conversion to AD along with APOE genotype. Zhang et al. [57] compared the genetic modality single-nucleotide polymorphism (SNP) with sMRI, 18F-FDG-PET, and CSF biomarkers, which were used to differentiate healthy control, MCI, and AD. They found FDG-PET is the best modality in terms of accuracy.

3.2 Amyloid beta PET

Aβ, the primary constituent of senile plaques, and tau tangles are hypothesized to play a primary role in the pathogenesis of AD, but it is still hard to identify the fundamental mechanisms [5860]. Aβ plaque in brain is one of the pathological hallmarks of AD [61,62]. Accumulation of Aβ peptide in the cerebral cortex is considered one cause of dementia in AD [63]. Numerous studies have involved in vivo PET imaging assessing cortical β-amyloid burden [6466].

Aβ imaging using PET has been recognized as one of the most important methods for the early diagnosis of AD [67]. Numerous candidate compounds have been tested for Aβ imaging, such as 11C-PiB [68], 18F-FDDNP [69], 11C-SB-13 [70], 18F-BAY94-9172 [71], 18F-AV-45 [72], 18F-flutemetamol [73, 74], 11C-AZD2184 [75], and 18F-ADZ4694 [76], 11C-BF227 and 18F-FACT [77].

Several amyloid PET studies examined genotypes, phenotypes, or gene–gene interactions. Ramanan et al. [78] reported the GWAS results with 18F-AV-45 reflecting the cerebral amyloid metabolism in AD for the first time. Swaminathan et al. [79] revealed the association between plasma Aβ from peripheral blood and cortical amyloid deposition on 11C-PiB. Hohman et al. [80] reported the relationship between SNPs involved in amyloid and tau pathophysiology with 18F-AV-45 PET.

Among the PET tracers, 11C-PiB, which has a high affinity for fibrillar Aβ, is a reliable biomarker of underlying AD pathology [68, 81]. It shows cortical uptake well paralleled with AD pathology [82, 83], has recently been approved for use by the Food and Drug Administration (FDA, April 2012) and the European Medicines Agency (January 2013). 18F-GE-067 (flutemetamol) and 18F-BAY94-9172 (florbetaben) have also been approved by the US FDA in the last 2 years [84, 85].

18F-Florbetapir (also known as 18F-AV-45) exhibits high affinity specific binding to amyloid plaques. 18F-AV-45 labels Aβ plaques in sections from patients with pathologically confirmed AD [72].

It was reported in several research groups that 18F-AV-45 PET imaging showed a reliability of both qualitative and quantitative assessments in AD patients, and Aβ+ increased with diagnostic category (healthy control < MCI < AD) [82, 86, 87]. Johnson et al. used 18F-AV-45 PET imaging to evaluate the amyloid deposition in both MCI and AD patients qualitatively and quantitatively, and found that amyloid burden increased with diagnostic category (MCI < AD), age, and APOEε4 carrier status [88]. Payoux et al. reported the equivocal amyloid PET scans using 18F-AV-45 associated with a specific pattern of clinical signs in a large population of non-demented older adults more than 70 years old [89].

More and more researchers consider combination and comparison of multiple PET tracers targeting amyloid plaque imaging together. Bruck et al. compared the prognostic ability of 11C-PiB PET, 18F-FDG-PET, and quantitative hippocampal volumes measured with MR imaging in predicting MCI to AD conversion. They found that the FDG-PET and 11C-PiB PET imaging are better in predicting MCI to AD conversion [90]. Hatashita et al. used 11C-PiB and FDG-PET imaging to identify MCI due to AD, 11C-PiB showed a higher sensitivity of 96.6 %, and FDG-PET added diagnostic value in predicting AD over a short period [91].

Besides, new Aβ imaging agents were radiosynthesized. Yousefi et al. radiosynthesized a new Aβ imaging agent 18F-FIBT, and compared the three different Aβ-targeted radiopharmaceuticals for PET imaging, including 18F-FIBT, 18F-florbetaben, and 11C-PiB [92]. 11C-AZD2184 is another new PET tracer developed for amyloid senile plaque imaging, and the kinetic behavior of 11C-AZD2184 is suitable for quantitative analysis and can be used in clinical examination without input function [75,93, 94].

4 Multimodality imaging: PET/MRI

Several diagnostic techniques, including MRI and PET, are employed for the diagnosis and monitoring of AD [95]. Multimodal imaging could provide more information in the formation and key molecular event of AD than single method. It drives the progression of neuroimaging research due to the recognition of the clinical benefits of multimodal data [96], and the better access to hybrid devices, such as PET/MRI [97].

Maier et al. evaluated the dynamics of 11C-PiB PET, 15O-H2O-PET, and ASL-MRI in transgenic AD mice and concluded that the AD-related decline of rCBF was caused by the cerebral Aβ angiopathy [98]. Edison et al. systematically compared 11C-PiB PET and MRI in AD, MCI patients, and controls. They thought that 11C-PiB PET was adequate for clinical diagnostic purpose, while MRI remained more appropriate for clinical research [99]. Zhou et al. investigated the interactions between multimodal PET/MRI in elder patients with MCI, AD, and healthy controls, and confirmed the invaluable application of amyloid PET and MRI in early diagnosis of AD [100]. Kim et al. reported that Aβ-weighted cortical thickness, which incorporates data from both MRI and amyloid PET imaging, is a consistent and objective imaging biomarker in AD [101].

5 Other imaging modalities

Multiphoton non-linear optical microscope imaging systems using ultrafast lasers have powerful advantages such as label-free detection, deep penetration of thick samples, high sensitivity, subcellular spatial resolution, 3D optical sectioning, chemical specificity, and minimum sample destruction [102, 103]. Coherent anti-Stokes–Raman scattering (CARS), two-photon excited fluorescence (TPEF), and second-harmonic generation (SHG) microscopy are the most widely used biomedical imaging techniques [104106].

 

Quantitative electroencephalographic and neuropsychological investigation of an alternative measure of frontal lobe executive functions: the Figure Trail Making Test

 Paul S. Foster, Valeria Drago, Brad J. Ferguson, Patti Kelly Harrison,David W. Harrison 

Brain Informatis    http://dx.doi.org:/10.1007/s40708-015-0025-z    http://link.springer.com/article/10.1007/s40708-015-0025-z/fulltext.html

The most frequently used measures of executive functioning are either sensitive to left frontal lobe functioning or bilateral frontal functioning. Relatively little is known about right frontal lobe contributions to executive functioning given the paucity of measures sensitive to right frontal functioning. The present investigation reports the development and initial validation of a new measure designed to be sensitive to right frontal lobe functioning, the Figure Trail Making Test (FTMT). The FTMT, the classic Trial Making Test, and the Ruff Figural Fluency Test (RFFT) were administered to 42 right-handed men. The results indicated a significant relationship between the FTMT and both the TMT and the RFFT. Performance on the FTMT was also related to high beta EEG over the right frontal lobe. Thus, the FTMT appears to be an equivalent measure of executive functioning that may be sensitive to right frontal lobe functioning. Applications for use in frontotemporal dementia, Alzheimer’s disease, and other patient populations are discussed.

Keywords – Frontal lobes, Executive functioning, Trail making test, Sequencing, Behavioral speed, Designs, Nonverbal, Neuropsychological assessment, Regulatory control, Effortful control

A recent survey indicated that the vast majority of neuropsychologists frequently assess executive functioning as part of their neuropsychological evaluations [1]. Surveys of neuropsychologists have indicated that the Trail Making Test (TMT), Controlled Oral Word Association Test (COWAT), Wisconsin Card Sorting Test (WCST), and the Stroop Color-Word Test (SCWT) are among the most commonly used instruments [1,2]. Further, the Rabin et al. [1] survey indicated that these same tests are among the most frequently used by neuropsychologists when specifically assessing executive or frontal lobe functioning. The frequent use of the TMT, WCST, and the SCWT, as well as the assumption that they are measures of executive functioning, led Demakis (2003–2004) to conduct a series of meta-analyses to determine the sensitivity of these test to detect frontal lobe dysfunction, particularly lateralized frontal lobe dysfunction. The findings indicated that the SCWT and Part A of the TMT [3], as well as the WCST [4], were all sensitive to frontal lobe dysfunction. However, only the SCWT differentiated between left and right frontal lobe dysfunction, with the worst performance among those with left frontal lobe dysfunction [3].

The finding of the Demakis [4] meta-analysis, that the WCST was not sensitive to lateralized frontal lobe dysfunction, is not surprising given the equivocal findings that have been reported. Whereas performance on the WCST is sensitive to frontal lobe dysfunction [5, 6], demonstration of lateralized frontal dysfunction has been quite problematic. Unilateral left or right dorsolateral frontal dysfunction has been associated with impaired performance on the WCST [6]. Fallgatter and Strik [7] found bilateral frontal lobe activation during performance of the WCST. However, other imaging studies have found right lateralized frontal lobe activation [8] and left lateralized frontal activation [9] in response to performance on the WCST. Further, left frontal lobe alpha power is negatively correlated with performance on the WCST [10]. Finally, patients with left frontal lobe tumors exhibit more impaired performance on the WCST than those with right frontal tumors [11].

Unlike the data for the WCST, more consistent findings have been reported regarding lateralized frontal lobe functioning for the other commonly used measures of executive functioning. For instance, as with the Demakis [3] study, many investigations have found the SCWT to be sensitive to left frontal lobe functioning, although the precise localization within the left frontal lobe has varied. Impaired performance on the SCWT results from left frontal lesions [12] and specifically from lesions localized to the left dorsolateral frontal lobe [13, 14], though bilateral frontal lesions have also yielded impaired performance [13, 14]. Further, studies using neuroimaging to investigate the neural basis of performance on the SCWT have indicated involvement of the left anterior cingulated cortex [15], left lateral prefrontal cortex [16], left inferior precentral sulcus [17], and the left dorsolateral frontal lobe [18].

Wide agreement exists among investigations of the frontal lateralization of verbal or lexical fluency to confrontation. Specifically, patients with left frontal lobe lesions are known to exhibit impaired performance on lexical fluency to confrontation tasks, relative to either patients with right frontal lesions [12, 19, 20] or controls [21]. A recent meta-analysis also indicated that the largest deficits in performance on measures of lexical fluency are associated with left frontal lobe lesions [22]. Troster et al. [23] found that, relative to patients with right pallidotomy, patients with left pallidotomy exhibited more impaired lexical fluency. Several neuroimaging investigations have further supported the role of the left frontal lobe in lexical fluency tasks [15, 2427]. Performance on lexical fluency tasks also varies as a function of lateral frontal lobe asymmetry, as assessed by electroencephalography [28].

The Trail Making Test is certainly among the most widely used tests [1] and perhaps the most widely researched. Various norms exist for the TMT (see [29]), with Tombaugh [30] providing the most recent comprehensive set of normative data. Different methods of analyzing and interpreting the data have also been proposed and used, including error analysis [13, 14, 3133], subtraction scores [13, 14, 34], and ratio scores [13, 14, 35].

Several different language versions of the test have been developed and reported, including Arabic [36], Chinese [37, 38], Greek [39], and Hebrew [40]. Numerous alternative versions of the TMT have been developed to address perceived shortcomings of the original TMT. For instance, the Symbol Trail Making Test [41] was developed to reduce the cultural confounds associated with the use of the Arabic numeral system and English alphabet in the original TMT. The Color Trails Test (CTT; [42]) was also developed to control for cultural confounds, although mixed results have been reported regarding whether the CTT is indeed analogous to the TMT [4345]. A version of the TMT for preschool children, the TRAILS-P, has also been reported [46].

Additionally, the Comprehensive Trail Making Test [47] was developed to control for perceived psychometric shortcomings of the original TMT (for a review see [48] and the Oral Trail Making Test (OTMT; [49]) was developed to reduce confounds associated with motor speed and visual search abilities, with research supporting the OTMT as an equivalent measure [50, 51]. Alternate forms of the TMT have also been developed to permit successive administrations [32, 52] and to assess the relative contributions of the requisite cognitive skills [53].

Delis et al. [54] stated that the continued development of new instrumentation for improving diagnosis and treatment is a critical undertaking in all health-related fields. Further, in their view, the field of neuropsychology has recognized the importance of continually striving to develop new clinical measures. Delis and colleagues developed the extensive Delis-Kaplan Executive Functioning System (D-KEFS; [55]) in the spirit of advancing the instrumentation of neuropsychology. The D-KEFS includes a Trail Making Test consisting of five separate conditions. The Number-Letter Switching condition involves a sequencing procedure similar to that of the classic TMT. The other four conditions are designed to assess the component processes involved in completing the Number-Letter Switching condition so that a precise analysis of the nature of any underlying dysfunction may be accomplished. Specifically, these additional components include Visual Scanning, Number Sequencing, Letter Sequencing, and Motor Speed.

Given that the TMT comprises numbers and letters and is a measure of executive functioning, it may preferentially involve the left frontal lobe. Although the literature is somewhat controversial, neuropsychological and neuroimaging studies seem to provide support for the sensitivity of the TMT to detect left frontal dysfunction [56]. Recent clinically oriented studies investigating frontal lobe involvement of the TMT using transcranial magnetic stimulation (TMS) and near-infrared spectroscopy (NIRS) also support this localization [57]. Performance on Part B of the TMT improved following repetitive TMS applied to the left dorsolateral frontal lobe [57].

With 9–13-year-old boys performing TMT Part B, Weber et al. [58] found a left lateralized increase in the prefrontal cortex in deoxygenated hemoglobin, an indicator of increased oxygen consumption. Moll et al. [59] demonstrated increased activation specific to the prefrontal cortex, especially the left prefrontal region, in healthy controls performing Part B of the TMT. Foster et al. [60] found a significant positive correlation between performance on Part A of the TMT and low beta (13–21 Hz) magnitude (μV) at the left lateral frontal lobe, but not at the right lateral frontal lobe. Finally, Stuss et al. [13, 14] found that patients with left dorsolateral frontal dysfunction evidenced more errors than patients with lesions in other areas of the frontal lobes and those patients with left frontal lesions were the slowest to complete the test.

Taken together, the possibility exists that the aforementioned tests are largely associated with left frontal lobe activity and the TMT, in particular, provides information concerning mental processing speed as well as cognitive flexibility and set-shifting. While some studies have found that deficits in visuomotor set-shifting are specific to the frontal lobe damage [61], others investigators have reported such impairment in patients with posterior brain lesions and widespread cerebral dysfunctions, including cerebellar damage [62] and Alzheimer disease [63]. Thus, it remains unclear whether impairments in visuomotor set-shifting are specific to frontal lobe dysfunction or whether they are non-specific and can result from more posterior or widespread brain dysfunction.

Compared to the collective knowledge we have regarding the cognitive roles of the left frontal lobe, relatively little is known about right frontal lobe contributions to executive functioning. This is likely a result of the dearth of tests that are associated with right frontal activity. The Ruff Figural Fluency Test (RFFT; [64]) is among the few standardized tests of right frontal lobe functioning and was listed as the 14th most commonly used instrument to assess executive functioning in the Rabin et al. [1] survey. The RFFT is known to be sensitive to right frontal lobe functioning [65, 66]; see also [67] pp. 297–298), as is a measure based on the RFFT [19].

The present investigation, with the same intent and spirit as that reported by Delis et al. [54], sought to develop and initially validate a measure of right frontal lobe functioning in an effort to attain a greater understanding of right frontal contributions to executive functioning and to advance the instrumentation of neuropsychology. To meet this objective, a version of the Trail Making Test comprising figures, as opposed to numbers and letters, was developed. The TMT was used as a model for the new test, referred to as the Figure Trail Making Test (FTMT), due to the high frequency of use, the volume of research conducted, and the ease of administration of the TMT. Given that the TMT and the FTMT are both measuring executive functioning, we felt that a moderate correlation would exist between these two measures. Specifically, we hypothesized that performance on the FTMT would be positively correlated with performance on the TMT, in terms of the total time required to complete each part of the tests, an additive and subtractive score, and a ratio score. The total time required to complete each part of the FTMT was also hypothesized to be negatively correlated with the total number of unique designs produced on the RFFT and positively correlated with the number of perseverative errors committed on the RFFT and the perseverative error ratio. We also sought to determine whether the TMT and the FTMT were measuring different constructs by conducting a factor analysis, anticipating that the two tests would load on separate factors.

Additionally, we sought to obtain neurophysiological evidence that the FTMT is sensitive to right frontal lobe functioning. Specifically, we used quantitative electroencephalography (QEEG) to measure electrical activity over the left and right frontal lobes. A previous investigation we conducted found that performance on Part A of the TMT was related to left frontal lobe (F7) low beta magnitude [60]. For the present investigation, we predicted that significant negative correlations would exist between performance on Parts A and B of the TMT and both low and high beta magnitude at the F7 electrode site. We further predicted that significant negative correlations would exist between performance on Parts C and D of the FTMT and both low and high beta magnitude at the F8 electrode site.

3 Discussion

The need for additional measures of executive functions and especially instruments which may provide implications relevant to cerebral laterality is clear. There remains especially a void for neuropsychological instruments using a TMT format, which may provide information pertaining to the functional integrity of the right frontal region. Consistent with the hypotheses forwarded, significant correlations were found between performance on the TMT and the FTMT, in terms of the raw time required to complete each respective part of the tests as well as the additive and subtraction scores. The fact that the ratio scores were not significantly correlated is not surprising given that research has generally indicated a lack of clinical utility for this score [13, 14, 35]. Given the present findings, the TMT and the FTMT appear to be equivalent measures of executive functioning. Further, the present findings not only suggest that the FTMT may be a measure of executive functioning but also extend the realm of executive functioning to the sequencing and set-shifting of nonverbal stimuli.

However, the finding of significant correlations between the TMT and the FTMT represents somewhat of a caveat in that the TMT has been found to be sensitive to left frontal lobe functioning [13, 14, 57, 59]. This would seem to suggest the possibility that the FTMT is also sensitive to left frontal lobe functioning. The possibility that FTMT is related to left frontal lobe functioning is tempered, though, by the fact that the many of the hypothesized correlations between performance on the RFFT and the FTMT were also significant. Performance on the RFFT is related to right frontal lobe functioning [65,66]. Thus, the significant correlations between the RFFT and the FTMT suggest that the FTMT may also be sensitive to right frontal lobe functioning. Additionally, it should also be noted that the TMT was not significantly correlated with performance on the RFFT, with the exception of the significant correlation between performance on the TMT Part A and the total number of unique designs produced on the RFFT. Taken together, the results suggest that the FTMT may be a measure of right frontal executive functioning.

Additional support for the sensitivity of the FTMT to right frontal lobe functioning is provided by the finding of a significant negative correlation between performance on Part D of the FTMT and high beta magnitude. We have previously used QEEG to provide neurophysiological validation of the RFFT [65] and the Rey Auditory Verbal Learning Test [70] and the present findings provide further support for the use of QEEG in validating neuropsychological tests. The lack of significant correlations between the TMT and either low or high beta magnitude may be related to a restricted range of scores on the TMT. As a whole, performance on the FTMT was more variable than performance on the TMT and this relatively restricted range for the TMT may have impacted the obtained correlations. Given the present findings, together with those of the Foster et al. [65, 70] investigations, further support is also provided for the use of EEG in establishing neurophysiological validation for neuropsychological tests.

The results from the factor analysis provide support for the contention that the FMT may be a measure of right frontal lobe activity and also provide initial discriminant validity for the FTMT. Specifically, Parts C and D of the FTMT were found to load on the same factor as the number of designs generated on the RFFT, although the time required to complete Part A of the TMT is also included. Additionally, the number of errors committed on Parts C and D of the FTMT comprises a single factor, separate from either the TMT or the RFFT. Although these results support the FTMT as a measure of nonverbal executive functioning, it would be helpful to conduct an additional factor analysis including additional measures of right frontal functioning, and perhaps other measures of right hemisphere functioning as marker variables.

We sought to develop a measure sensitive to right frontal lobe functioning due to the paucity of such tests and the potentially important uses that right frontal lobe tests may have clinically. Tests of right frontal lobe functioning may, for instance, be useful in identifying and distinguishing left versus right frontotemporal dementia (FTD). Research has indicated that FTD is associated with cerebral atrophy at the right dorsolateral frontal and left premotor cortices [71]. Fukui and Kertesz [72] found right frontal lobe volume reduction in FTD relative to Alzheimer’s disease and progressive nonfluent aphasia. Some have suggested that FTD should not be considered as a unitary disorder and that neuropsychological testing may aid in differentially diagnosing left versus right FTD [73].

Whereas right FTD has been associated with more errors and perseverative responses on the Wisconsin Card Sorting Test (WCST), left FTD has been associated with significantly worse performance on the Boston Naming Test (BNT) and the Stroop Color-Word test [73]. Razani et al. [74] also distinguished between left and right FTD in finding that left FTD performed worse on the BNT and the right FTD patients performed worse on the WCST. However, as noted earlier, the WCST has been associated with left frontal activity [9], right frontal activation [8], and bilateral frontal activation [7]. Further, patients with left frontal tumors perform worse than those with right frontal tumors [11].

Patients with FTD that predominantly involves the right frontotemporal region have behavioral and emotional abnormalities and those with predominantly left frontotemporal region damage have a loss of lexical semantic knowledge. Patients, in whom neural degeneration begins on the left side, often present to the clinicians at an early stage of the disease due to the presence of language abnormalities, but maintain their emotion processing abilities, being preserved the right anterior temporal lobe. However, as this disease advances, the disease may progress to the right frontotemporal regions. Tests sensitive to right frontal lobe functioning may be useful tools to identify in advance the course of the disease, providing immediate and specific treatments and informing the caregivers on the possible prospective frame of the disease.

A potentially more important use of tests sensitive to right frontal lobe functioning, though, may be in predicting dementia patients that will develop significant and disruptive behavioral deficits. Research has found that approximately 92 % of right-sided FTD patients exhibit socially undesirable behaviors as their initial symptom, as compared to only 11 % of left-sided FTD patients [75]. Behavioral deficits in FTD are associated with gray matter loss at the dorsomedial frontal region, particularly on the right [76].

Alzheimer’s disease (AD) is also often associated with significant behavioral disturbances. Even AD patients with mild dementia are noted to exhibit behavioral deficits such as delusions, hallucinations, agitation, dysphoria, anxiety, apathy, and irritability [77]. Indeed, Shimabukuro et al. [77] found that regardless of dementia severity, over half of all AD patients exhibited apathy, delusions, irritability, dysphoria, and anxiety. Delusions in AD patients are associated with relative right frontal hypoperfusion as indicated by SPECT imaging [78, 79]. Further, positron emission tomography (PET) has indicated that AD patients exhibiting delusions exhibit hypometabolism at the right superior dorsolateral frontal and right inferior frontal pole [80].

Although research clearly implicates right frontal lobe dysfunction in the expression of behavioral deficits, data from neuropsychological testing are not as clear. Negative symptoms in patients with AD and FTD have been related to measures of nonverbal and verbal executive functioning as well as verbal memory [81]. Positive symptoms, in contrast, were related to constructional skills and attention. However, Staff et al. [78] failed to dissociate patients with delusions from those without delusions based on neuropsychological test performance, despite significant differences existing in right frontal and limbic functioning as revealed by functional imaging. The inclusion of other measures of right frontal lobe functioning may result in improved neuropsychological differentiation of dementia patients with and without significant behavioral disturbances. Further, it may be possible to predict early in the disease process those patients that will ultimately develop behavioral disturbances with improved measures of right frontal functioning. Predicting those that may develop behavioral problems will permit earlier treatment and will provide the family with more time to prepare for the potential emergence of such difficulties. Certainly, future research needs to be conducted that incorporates measures of right and left frontal lobe functioning in regression analyses to determine the plausibility of such prediction.

Tests sensitive to right frontal lobe functioning may also be useful in identifying more subtle right frontal lobe dysfunction and the cognitive and behavioral changes that follow. The right frontal lobe mediates language melody or prosody and forms a cohesive discourse, interprets abstract communication in spoken and written languages, and interprets the inferred relationships involved in communications. Subtle difficulties in interpreting abstract meaning in communication, comprehending metaphors, and even understanding jokes that are often seen in right frontal lobe stroke patients may not be detected by the family and may also be under diagnosed by clinicians [82]. Further, patients with right frontal lobe lesions are generally more euphoric and unconcerned, often minimizing their symptoms [82] or denying the illness, which may delay referral to a clinician and diagnosis.

Attention deficit hyperactivity disorder (ADHD) is a neurological disease characterized by motor inhibition deficit, problems with cognitive flexibility, social disruption, and emotional disinhibition [83, 84]. Functional MRI studies reveal reduced right prefrontal activation during “frontal tasks,” such as go/no go [85], Stroop [86], and attention task performance [87]. The right frontal lobe deficit hypothesis is further supported by structural studies [88, 89]. Tests of right frontal lobe functioning may be useful in further characterizing the nature of this deficit and in specifying the likely hemispheric locus of dysfunction.

To summarize, we feel that right frontal lobe functioning has been relatively neglected in neuropsychological assessment and that many uses for such tests exist. Our intent was to develop a test purportedly sensitive to right frontal functioning that would be easy and quick to administer in a clinical setting. However, we are certainly not meaning to assert that our FTMT would be applicable in all the aforementioned conditions. Additional research should be conducted to determine the precise clinical utility of the FTMT.

Further validation of the FTMT should also be undertaken. Establishing convergent validation may involve correlating tests measuring the same domain, such as executive functioning. This was initially accomplished in the present investigation through the significant correlations between the TMT and the FTMT. Additionally, convergent validation may also involve correlating tests that purportedly measure the same region of the brain. This was also initially accomplished in the present investigation through the significant correlations between the FTMT and the RFFT. However, additional convergent validation certainly needs to be obtained, as well as validation using patient populations and neurophysiological validation.

We are currently collecting data that hopefully will provide neurophysiological validation of the FTMT. Certainly, though, it is hoped that the present investigation will not only stimulate further research seeking to validate the FTMT and provide more comprehensive normative data, but also stimulate research investigating whether the FTMT or other measures of right frontal lobe functioning may be used to predict patients that will develop behavioral disturbances.

 

World’s Greatest Literature Reveals Multifractals, Cascades of Consciousness

http://www.scientificcomputing.com/news/2016/01/worlds-greatest-literature-reveals-multifractals-cascades-consciousness

http://www.scientificcomputing.com/sites/scientificcomputing.com/files/Worlds_Greatest_Literature_Reveals_Multifractals_Cascades_of_Consciousness_440.jpg

Multifractal analysis of Finnegan’s Wake by James Joyce. The ideal shape of the graph is virtually indistinguishable from the results for purely mathematical multifractals. The horizontal axis represents the degree of singularity, and the vertical axis shows the spectrum of singularity. Courtesy of IFJ PAN

Arthur Conan Doyle, Charles Dickens, James Joyce, William Shakespeare and JRR Tolkien. Regardless of the language they were working in, some of the world’s greatest writers appear to be, in some respects, constructing fractals. Statistical analysis, however, revealed something even more intriguing. The composition of works from within a particular genre was characterized by the exceptional dynamics of a cascading (avalanche) narrative structure. This type of narrative turns out to be multifractal. That is, fractals of fractals are created.

As far as many bookworms are concerned, advanced equations and graphs are the last things which would hold their interest, but there’s no escape from the math. Physicists from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ) in Cracow, Poland, performed a detailed statistical analysis of more than one hundred famous works of world literature, written in several languages and representing various literary genres. The books, tested for revealing correlations in variations of sentence length, proved to be governed by the dynamics of a cascade. This means that the construction of these books is, in fact, a fractal. In the case of several works, their mathematical complexity proved to be exceptional, comparable to the structure of complex mathematical objects considered to be multifractal. Interestingly, in the analyzed pool of all the works, one genre turned out to be exceptionally multifractal in nature.

Fractals are self-similar mathematical objects: when we begin to expand one fragment or another, what eventually emerges is a structure that resembles the original object. Typical fractals, especially those widely known as the Sierpinski triangle and the Mandelbrot set, are monofractals, meaning that the pace of enlargement in any place of a fractal is the same, linear: if they at some point were rescaled x number of times to reveal a structure similar to the original, the same increase in another place would also reveal a similar structure.

Multifractals are more highly advanced mathematical structures: fractals of fractals. They arise from fractals ‘interwoven’ with each other in an appropriate manner and in appropriate proportions. Multifractals are not simply the sum of fractals and cannot be divided to return back to their original components, because the way they weave is fractal in nature. The result is that, in order to see a structure similar to the original, different portions of a multifractal need to expand at different rates. A multifractal is, therefore, non-linear in nature.

“Analyses on multiple scales, carried out using fractals, allow us to neatly grasp information on correlations among data at various levels of complexity of tested systems. As a result, they point to the hierarchical organization of phenomena and structures found in nature. So, we can expect natural language, which represents a major evolutionary leap of the natural world, to show such correlations as well. Their existence in literary works, however, had not yet been convincingly documented. Meanwhile, it turned out that, when you look at these works from the proper perspective, these correlations appear to be not only common, but in some works they take on a particularly sophisticated mathematical complexity,” says Professor Stanislaw Drozdz, IFJ PAN, Cracow University of Technology.

The study involved 113 literary works written in English, French, German, Italian, Polish, Russian and Spanish by such famous figures as Honore de Balzac, Arthur Conan Doyle, Julio Cortazar, Charles Dickens, Fyodor Dostoevsky, Alexandre Dumas, Umberto Eco, George Elliot, Victor Hugo, James Joyce, Thomas Mann, Marcel Proust, Wladyslaw Reymont, William Shakespeare, Henryk Sienkiewicz, JRR Tolkien, Leo Tolstoy and Virginia Woolf, among others. The selected works were no less than 5,000 sentences long, in order to ensure statistical reliability.

To convert the texts to numerical sequences, sentence length was measured by the number of words (an alternative method of counting characters in the sentence turned out to have no major impact on the conclusions). The dependences were then searched for in the data — beginning with the simplest, i.e. linear. This is the posited question: if a sentence of a given length is x times longer than the sentences of different lengths, is the same aspect ratio preserved when looking at sentences respectively longer or shorter?

“All of the examined works showed self-similarity in terms of organization of the lengths of sentences. Some were more expressive — here The Ambassadors by Henry James stood out — while others to far less of an extreme, as in the case of the French seventeenth-century romance Artamene ou le Grand Cyrus. However, correlations were evident and, therefore, these texts were the construction of a fractal,” comments Dr. Pawel Oswiecimka (IFJ PAN), who also noted that fractality of a literary text will, in practice, never be as perfect as in the world of mathematics. It is possible to magnify mathematical fractals up to infinity, while the number of sentences in each book is finite and, at a certain stage of scaling, there will always be a cut-off in the form of the end of the dataset.

Things took a particularly interesting turn when physicists from IFJ PAN began tracking non-linear dependence, which in most of the studied works was present to a slight or moderate degree. However, more than a dozen works revealed a very clear multifractal structure, and almost all of these proved to be representative of one genre, that of stream of consciousness. The only exception was the Bible, specifically the Old Testament, which has, so far, never been associated with this literary genre.

“The absolute record in terms of multifractality turned out to be Finnegan’s Wakeby James Joyce. The results of our analysis of this text are virtually indistinguishable from ideal, purely mathematical multifractals,” says Drozdz.

The most multifractal works also included A Heartbreaking Work of Staggering Genius by Dave Eggers, Rayuela by Julio Cortazar, The US Trilogy by John Dos Passos, The Waves by Virginia Woolf, 2666 by Roberto Bolano, and Joyce’sUlysses. At the same time, a lot of works usually regarded as stream of consciousness turned out to show little correlation to multifractality, as it was hardly noticeable in books such as Atlas Shrugged by Ayn Rand and A la recherche du temps perdu by Marcel Proust.

“It is not entirely clear whether stream of consciousness writing actually reveals the deeper qualities of our consciousness, or rather the imagination of the writers. It is hardly surprising that ascribing a work to a particular genre is, for whatever reason, sometimes subjective. We see, moreover, the possibility of an interesting application of our methodology: it may someday help in a more objective assignment of books to one genre or another,” notes Drozdz.

Multifractal analyses of literary texts carried out by the IFJ PAN have been published in Information Sciences, the journal of computer science. The publication has undergone rigorous verification: given the interdisciplinary nature of the subject, editors immediately appointed up to six reviewers.

Citation: “Quantifying origin and character of long-range correlations in narrative texts” S. Drożdż, P. Oświęcimka, A. Kulig, J. Kwapień, K. Bazarnik, I. Grabska-Gradzińska, J. Rybicki, M. Stanuszek; Information Sciences, vol. 331, 32–44, 20 February 2016; DOI: 10.1016/j.ins.2015.10.023

 

New Quantum Approach to Big Data could make Impossibly Complex Problems Solvable

David L. Chandler, MIT

http://www.scientificcomputing.com/news/2016/01/new-quantum-approach-big-data-could-make-impossibly-complex-problems-solvable

 

http://www.scientificcomputing.com/sites/scientificcomputing.com/files/New_Quantum_Approach_to_Big_Data_could_make_Impossibly_Complex_Problems_Solvable_440.jpg

This diagram demonstrates the simplified results that can be obtained by using quantum analysis on enormous, complex sets of data. Shown here are the connections between different regions of the brain in a control subject (left) and a subject under the influence of the psychedelic compound psilocybin (right). This demonstrates a dramatic increase in connectivity, which explains some of the drug’s effects (such as “hearing” colors or “seeing” smells). Such an analysis, involving billions of brain cells, would be too complex for conventional techniques, but could be handled easily by the new quantum approach, the researchers say. Courtesy of the researchers

From gene mapping to space exploration, humanity continues to generate ever-larger sets of data — far more information than people can actually process, manage or understand.

Machine learning systems can help researchers deal with this ever-growing flood of information. Some of the most powerful of these analytical tools are based on a strange branch of geometry called topology, which deals with properties that stay the same even when something is bent and stretched every which way.

Such topological systems are especially useful for analyzing the connections in complex networks, such as the internal wiring of the brain, the U.S. power grid, or the global interconnections of the Internet. But even with the most powerful modern supercomputers, such problems remain daunting and impractical to solve. Now, a new approach that would use quantum computers to streamline these problems has been developed by researchers at MIT, the University of Waterloo, and the University of Southern California.

The team describes their theoretical proposal this week in the journal Nature Communications. Seth Lloyd, the paper’s lead author and the Nam P. Suh Professor of Mechanical Engineering, explains that algebraic topology is key to the new method. This approach, he says, helps to reduce the impact of the inevitable distortions that arise every time someone collects data about the real world.

In a topological description, basic features of the data (How many holes does it have? How are the different parts connected?) are considered the same no matter how much they are stretched, compressed, or distorted. Lloyd explains that it is often these fundamental topological attributes “that are important in trying to reconstruct the underlying patterns in the real world that the data are supposed to represent.”

It doesn’t matter what kind of dataset is being analyzed, he says. The topological approach to looking for connections and holes “works whether it’s an actual physical hole, or the data represents a logical argument and there’s a hole in the argument. This will find both kinds of holes.”

Using conventional computers, that approach is too demanding for all but the simplest situations. Topological analysis “represents a crucial way of getting at the significant features of the data, but it’s computationally very expensive,” Lloyd says. “This is where quantum mechanics kicks in.” The new quantum-based approach, he says, could exponentially speed up such calculations.

Lloyd offers an example to illustrate that potential speedup: If you have a dataset with 300 points, a conventional approach to analyzing all the topological features in that system would require “a computer the size of the universe,” he says. That is, it would take 2300 (two to the 300th power) processing units — approximately the number of all the particles in the universe. In other words, the problem is simply not solvable in that way.

“That’s where our algorithm kicks in,” he says. Solving the same problem with the new system, using a quantum computer, would require just 300 quantum bits — and a device this size may be achieved in the next few years, according to Lloyd.

“Our algorithm shows that you don’t need a big quantum computer to kick some serious topological butt,” he says.

There are many important kinds of huge datasets where the quantum-topological approach could be useful, Lloyd says, for example understanding interconnections in the brain. “By applying topological analysis to datasets gleaned by electroencephalography or functional MRI, you can reveal the complex connectivity and topology of the sequences of firing neurons that underlie our thought processes,” he says.

The same approach could be used for analyzing many other kinds of information. “You could apply it to the world’s economy, or to social networks, or almost any system that involves long-range transport of goods or information,” Lloyd says. But the limits of classical computation have prevented such approaches from being applied before.

While this work is theoretical, “experimentalists have already contacted us about trying prototypes,” he says. “You could find the topology of simple structures on a very simple quantum computer. People are trying proof-of-concept experiments.”

Ignacio Cirac, a professor at the Max Planck Institute of Quantum Optics in Munich, Germany, who was not involved in this research, calls it “a very original idea, and I think that it has a great potential.” He adds “I guess that it has to be further developed and adapted to particular problems. In any case, I think that this is top-quality research.”

The team also included Silvano Garnerone of the University of Waterloo in Ontario, Canada, and Paolo Zanardi of the Center for Quantum Information Science and Technology at the University of Southern California. The work was supported by the Army Research Office, Air Force Office of Scientific Research, Defense Advanced Research Projects Agency, Multidisciplinary University Research Initiative of the Office of Naval Research, and the National Science Foundation.

 

Beyond Chess: Computer Beats Human in Ancient Chinese Game

http://www.rdmag.com/news/2016/01/beyond-chess-computer-beats-human-ancient-chinese-game

http://www.rdmag.com/sites/rdmag.com/files/rd1601_chess.jpg

A player places a black stone while his opponent waits to place a white one as they play Go, a game of strategy, in the Seattle Go Center, Tuesday, April 30, 2002. The game, which originated in China more than 2,500 years ago, involves two players who take turns putting markers on a grid. The object is to surround more area on the board with the markers than one’s opponent, as well as capturing the opponent’s pieces by surrounding them. A paper released Wednesday, Jan. 27, 2016 describes how a computer program has beaten a human master at the complex board game, marking significant advance for development of artificial intelligence. (AP Photo/Cheryl Hatch)

 

A computer program has beaten a human champion at the ancient Chinese board game Go, marking a significant advance for development of artificial intelligence.

The program had taught itself how to win, and its developers say its learning strategy may someday let computers help solve real-world problems like making medical diagnoses and pursuing scientific research.

The program and its victory are described in a paper released Wednesday by the journal Nature.

Computers previously have surpassed humans for other games, including chess, checkers and backgammon. But among classic games, Go has long been viewed as the most challenging for artificial intelligence to master.

Go, which originated in China more than 2,500 years ago, involves two players who take turns putting markers on a checkerboard-like grid. The object is to surround more area on the board with the markers than one’s opponent, as well as capturing the opponent’s pieces by surrounding them.

While the rules are simple, playing it well is not. It’s “probably the most complex game ever devised by humans,” Dennis Hassabis of Google DeepMind in London, one of the study authors, told reporters Tuesday.

The new program, AlphaGo, defeated the European champion in all five games of a match in October, the Nature paper reports.

In March, AlphaGo will face legendary player Lee Sedol in Seoul, South Korea, for a $1 million prize, Hassabis said.

Martin Mueller, a computing science professor at the University of Alberta in Canada who has worked on Go programs for 30 years but didn’t participate in AlphaGo, said the new program “is really a big step up from everything else we’ve seen…. It’s a very, very impressive piece of work.”

 

 

Biological Origin of Schizophrenia

Excessive ‘pruning’ of connections between neurons in brain predisposes to disease

http://hms.harvard.edu/sites/default/files/uploads/news/McCarroll_C4_600x400.jpg

Imaging studies showed C4 (in green) located at the synapses of primary human neurons. Image: Heather de Rivera, McCarroll lab

 PAUL GOLDSMITH    http://hms.harvard.edu/news/biological-origin-schizophrenia

The risk of schizophrenia increases if a person inherits specific variants in a gene related to “synaptic pruning”—the elimination of connections between neurons—according to a study from Harvard Medical School, the Broad Institute and Boston Children’s Hospital. The findings were based on genetic analysis of nearly 65,000 people.

The study represents the first time that the origin of this psychiatric disease has been causally linked to specific gene variants and a biological process.

Get more HMS news here

It also helps explain two decades-old observations: synaptic pruning is particularly active during adolescence, which is the typical period of onset for symptoms of schizophrenia, and the brains of schizophrenic patients tend to show fewer connections between neurons.

The gene, complement component 4 (C4), plays a well-known role in the immune system. It has now been shown to also play a key role in brain development and schizophrenia risk. The insight may allow future therapeutic strategies to be directed at the disorder’s roots, rather than just its symptoms.

The study, which appears online Jan. 27 in Nature, was led by HMS researchers at the Broad Institute’s Stanley Center for Psychiatric Research and Boston Children’s. They include senior author Steven McCarroll, HMS associate professor of genetics and director of genetics for the Stanley Center; Beth Stevens, HMS assistant professor of neurology at Boston Children’s and institute member at the Broad; Michael Carroll, HMS professor of pediatrics at Boston Children’s; and first author Aswin Sekar, an MD-PhD student at HMS.

The study has the potential to reinvigorate translational research on a debilitating disease. Schizophrenia afflicts approximately 1 percent people worldwide and is characterized by hallucinations, emotional withdrawal and a decline in cognitive function. These symptoms most frequently begin in patients when they are teenagers or young adults.

“These results show that it is possible to go from genetic data to a new way of thinking about how a disease develops—something that has been greatly needed.”

First described more than 130 years ago, schizophrenia lacks highly effective treatments and has seen few biological or medical breakthroughs over the past half-century.

In the summer of 2014, an international consortium led by researchers at the Stanley Center identified more than 100 regions in the human genome that carry risk factors for schizophrenia.

The newly published study now reports the discovery of the specific gene underlying the strongest of these risk factors and links it to a specific biological process in the brain.

“Since schizophrenia was first described over a century ago, its underlying biology has been a black box, in part because it has been virtually impossible to model the disorder in cells or animals,” said McCarroll. “The human genome is providing a powerful new way in to this disease. Understanding these genetic effects on risk is a way of prying open that black box, peering inside and starting to see actual biological mechanisms.”

“This study marks a crucial turning point in the fight against mental illness,” said Bruce Cuthbert, acting director of the National Institute of Mental Health. “Because the molecular origins of psychiatric diseases are little-understood, efforts by pharmaceutical companies to pursue new therapeutics are few and far between. This study changes the game. Thanks to this genetic breakthrough we can finally see the potential for clinical tests, early detection, new treatments and even prevention.”

The path to discovery

The discovery involved the collection of DNA from more than 100,000 people, detailed analysis of complex genetic variation in more than 65,000 human genomes, development of an innovative analytical strategy, examination of postmortem brain samples from hundreds of people and the use of animal models to show that a protein from the immune system also plays a previously unsuspected role in the brain.

Over the past five years, Stanley Center geneticists and collaborators around the world collected more than 100,000 human DNA samples from 30 different countries to locate regions of the human genome harboring genetic variants that increase the risk of schizophrenia. The strongest signal by far was on chromosome 6, in a region of DNA long associated with infectious disease. This caused some observers to suggest that schizophrenia might be triggered by an infectious agent. But researchers had no idea which of the hundreds of genes in the region was actually responsible or how it acted.

Based on analyses of the genetic data, McCarroll and Sekar focused on a region containing the C4 gene. Unlike most genes, C4 has a high degree of structural variability. Different people have different numbers of copies and different types of the gene.

McCarroll and Sekar developed a new molecular technique to characterize the C4 gene structure in human DNA samples. They also measured C4 gene activity in nearly 700 post-mortem brain samples.

They found that the C4 gene structure (DNA) could predict the C4 gene activity (RNA) in each person’s brain. They then used this information to infer C4 gene activity from genome data from 65,000 people with and without schizophrenia.

These data revealed a striking correlation. People who had particular structural forms of the C4 gene showed higher expression of that gene and, in turn, had a higher risk of developing schizophrenia.

Connecting cause and effect through neuroscience

But how exactly does C4—a protein known to mark infectious microbes for destruction by immune cells—affect the risk of schizophrenia?

Answering this question required synthesizing genetics and neurobiology.

Stevens, a recent recipient of a MacArthur Foundation “genius grant,” had found that other complement proteins in the immune system also played a role in brain development. These results came from studying an experimental model of synaptic pruning in the mouse visual system.

“This discovery enriches our understanding of the complement system in brain development and in disease, and we could not have made that leap without the genetics.”

Carroll had long studied C4 for its role in immune disease, and developed mice with different numbers of copies of C4.

The three labs set out to study the role of C4 in the brain.

They found that C4 played a key role in pruning synapses during maturation of the brain. In particular, they found that C4 was necessary for another protein—a complement component called C3—to be deposited onto synapses as a signal that the synapses should be pruned. The data also suggested that the more C4 activity an animal had, the more synapses were eliminated in its brain at a key time in development.

The findings may help explain the longstanding mystery of why the brains of people with schizophrenia tend to have a thinner cerebral cortex (the brain’s outer layer, responsible for many aspects of cognition) with fewer synapses than do brains of unaffected individuals. The work may also help explain why the onset of schizophrenia symptoms tends to occur in late adolescence.

The human brain normally undergoes widespread synapse pruning during adolescence, especially in the cerebral cortex. Excessive synaptic pruning during adolescence and early adulthood, due to increased complement (C4) activity, could lead to the cognitive symptoms seen in schizophrenia.

“Once we had the genetic findings in front of us we started thinking about the possibility that complement molecules are excessively tagging synapses in the developing brain,” Stevens said.

“This discovery enriches our understanding of the complement system in brain development and in disease, and we could not have made that leap without the genetics,” she said. “We’re far from having a treatment based on this, but it’s exciting to think that one day we might be able to turn down the pruning process in some individuals and decrease their risk.”

Opening a path toward early detection and potential therapies

Beyond providing the first insights into the biological origins of schizophrenia, the work raises the possibility that therapies might someday be developed that could turn down the level of synaptic pruning in people who show early symptoms of schizophrenia.

This would be a dramatically different approach from current medical therapies, which address only a specific symptom of schizophrenia—psychosis—rather than the disorder’s root causes, and which do not stop cognitive decline or other symptoms of the illness.

The researchers emphasize that therapies based on these findings are still years down the road. Still, the fact that much is already known about the role of complement proteins in the immune system means that researchers can tap into a wealth of existing knowledge to identify possible therapeutic approaches. For example, anticomplement drugs are already under development for treating other diseases.

“In this area of science, our dream has been to find disease mechanisms that lead to new kinds of treatments,” said McCarroll. “These results show that it is possible to go from genetic data to a new way of thinking about how a disease develops—something that has been greatly needed.”

This work was supported by the Broad Institute’s Stanley Center for Psychiatric Research and by the National Institutes of Health (grants U01MH105641, R01MH077139 and T32GM007753).

Adapted from a Broad Institute news release.

 

Scientists open the ‘black box’ of schizophrenia with dramatic genetic discovery

Amy Ellis Nutt    https://www.washingtonpost.com/news/speaking-of-science/wp/2016/01/27/scientists-open-the-black-box-of-schizophrenia-with-dramatic-genetic-finding/

 

Scientists Prune Away Schizophrenia’s Hidden Genetic Mechanisms

http://www.genengnews.com/gen-news-highlights/scientists-prune-away-schizophrenia-s-hidden-genetic-mechanisms/81252297/

https://youtu.be/s0y4equOTLg

A landmark study has revealed that a person’s risk of schizophrenia is increased if they inherit specific variants in a gene related to “synaptic pruning”—the elimination of connections between neurons. The findings represent the first time that the origin of this devastating psychiatric disease has been causally linked to specific gene variants and a biological process.

http://www.genengnews.com/Media/images/GENHighlight/thumb_107629_web2209513618.jpg

The site in Chromosome 6 harboring the gene C4 towers far above other risk-associated areas on schizophrenia’s genomic “skyline,” marking its strongest known genetic influence. The new study is the first to explain how specific gene versions work biologically to confer schizophrenia risk. [Psychiatric Genomics Consortium]

  • A new study by researchers at the Broad Institute’s Stanley Center for Psychiatric Research, Harvard Medical School, and Boston Children’s Hospital genetically analyzed nearly 65,000 people and revealed that an individual’s risk of schizophrenia is increased if they inherited distinct variants in a gene related to “synaptic pruning”—the elimination of connections between neurons. This new data represents the first time that the origin of this psychiatric disease has been causally linked to particular gene variants and a biological process.

The investigators discovered that versions of a gene commonly thought to be involved in immune function might trigger a runaway pruning of an adolescent brain’s still-maturing communications infrastructure. The researchers described a scenario where patients with schizophrenia show fewer such connections between neurons or synapses.

“Normally, pruning gets rid of excess connections we no longer need, streamlining our brain for optimal performance, but too much pruning can impair mental function,” explained Thomas Lehner, Ph.D., director of the Office of Genomics Research Coordination at the NIH’s National Institute of Mental Health (NIMH), which co-funded the study along with the Stanley Center for Psychiatric Research at the Broad Institute and other NIH components. “It could help explain schizophrenia’s delayed age-of-onset of symptoms in late adolescence and early adulthood and shrinkage of the brain’s working tissue. Interventions that put the brakes on this pruning process-gone-awry could prove transformative.”

The gene the research team called into question, dubbed C4 (complement component 4), was associated with the largest risk for the disorder. C4’s role represents some of the most compelling evidence, to date, linking specific gene versions to a biological process that could cause at least some cases of the illness.

The findings from this study were published recently in Nature through an article entitled “Schizophrenia risk from complex variation of complement component 4.”

“Since schizophrenia was first described over a century ago, its underlying biology has been a black box, in part because it has been virtually impossible to model the disorder in cells or animals,” noted senior study author Steven McCarroll, Ph.D., director of genetics for the Stanley Center and an associate professor of genetics at Harvard Medical School. “The human genome is providing a powerful new way into this disease. Understanding these genetic effects on risk is a way of prying open that block box, peering inside and starting to see actual biological mechanisms.”

Dr. McCarroll and his colleagues found that a stretch of chromosome 6 encompassing several genes known to be involved in immune function emerged as the strongest signal associated with schizophrenia risk in genome-wide analyses. Yet conventional genetics failed to turn up any specific gene versions there that were linked to schizophrenia.

In order to uncover how the immune-related site confers risk for the mental disorder, the scientists mounted a search for cryptic genetic influences that might generate unconventional signals. C4, a gene with known roles in immunity, emerged as a prime suspect because it is unusually variable across individuals.

Upon further investigation into the complexities of how such structural variation relates to the gene’s level of expression and how that, in turn, might link to schizophrenia, the team discovered structurally distinct versions that affect expression of two main forms of the gene within the brain. The more a version resulted in expression of one of the forms, called C4A, the more it was associated with schizophrenia. The greater number of copies an individual had of the suspect versions, the more C4 switched on and the higher their risk of developing schizophrenia. Furthermore, the C4 protein turned out to be most prevalent within the cellular machinery that supports connections between neurons.

“Once we had the genetic findings in front of us we started thinking about the possibility that complement molecules are excessively tagging synapses in the developing brain,” remarked co-author Beth Stevens, Ph.D. a neuroscientist and assistant professor of neurology at Boston Children’s Hospital and institute member at the Broad. “This discovery enriches our understanding of the complement system in brain development and disease, and we could not have made that leap without the genetics. We’re far from having a treatment based on this, but it’s exciting to think that one day we might be able to turn down the pruning process in some individuals and decrease their risk.”

“This study marks a crucial turning point in the fight against mental illness. It changes the game,” added acting NIMH director Bruce Cuthbert, Ph.D. “Because the molecular origins of psychiatric diseases are little-understood, efforts by pharmaceutical companies to pursue new therapeutics are few and far between. This study changes the game. Thanks to this genetic breakthrough, we can finally see the potential for clinical tests, early detection, new treatments, and even prevention.”

 

Connecting cause and effect through neuroscience

But how exactly does C4—a protein known to mark infectious microbes for destruction by immune cells—affect the risk of schizophrenia?

Answering this question required synthesizing genetics and neurobiology.

Stevens, a recent recipient of a MacArthur Foundation “genius grant,” had found that other complement proteins in the immune system also played a role in brain development. These results came from studying an experimental model of synaptic pruning in the mouse visual system.

“This discovery enriches our understanding of the complement system in brain development and in disease, and we could not have made that leap without the genetics.”

Carroll had long studied C4 for its role in immune disease, and developed mice with different numbers of copies of C4.

The three labs set out to study the role of C4 in the brain.

They found that C4 played a key role in pruning synapses during maturation of the brain. In particular, they found that C4 was necessary for another protein—a complement component called C3—to be deposited onto synapses as a signal that the synapses should be pruned. The data also suggested that the more C4 activity an animal had, the more synapses were eliminated in its brain at a key time in development.

The findings may help explain the longstanding mystery of why the brains of people with schizophrenia tend to have a thinner cerebral cortex (the brain’s outer layer, responsible for many aspects of cognition) with fewer synapses than do brains of unaffected individuals. The work may also help explain why the onset of schizophrenia symptoms tends to occur in late adolescence.

The human brain normally undergoes widespread synapse pruning during adolescence, especially in the cerebral cortex. Excessive synaptic pruning during adolescence and early adulthood, due to increased complement (C4) activity, could lead to the cognitive symptoms seen in schizophrenia.

“Once we had the genetic findings in front of us we started thinking about the possibility that complement molecules are excessively tagging synapses in the developing brain,” Stevens said.

“This discovery enriches our understanding of the complement system in brain development and in disease, and we could not have made that leap without the genetics,” she said. “We’re far from having a treatment based on this, but it’s exciting to think that one day we might be able to turn down the pruning process in some individuals and decrease their risk.”

Opening a path toward early detection and potential therapies

Beyond providing the first insights into the biological origins of schizophrenia, the work raises the possibility that therapies might someday be developed that could turn down the level of synaptic pruning in people who show early symptoms of schizophrenia.

This would be a dramatically different approach from current medical therapies, which address only a specific symptom of schizophrenia—psychosis—rather than the disorder’s root causes, and which do not stop cognitive decline or other symptoms of the illness.

The researchers emphasize that therapies based on these findings are still years down the road. Still, the fact that much is already known about the role of complement proteins in the immune system means that researchers can tap into a wealth of existing knowledge to identify possible therapeutic approaches. For example, anticomplement drugs are already under development for treating other diseases.

“In this area of science, our dream has been to find disease mechanisms that lead to new kinds of treatments,” said McCarroll. “These results show that it is possible to go from genetic data to a new way of thinking about how a disease develops—something that has been greatly needed.”

This work was supported by the Broad Institute’s Stanley Center for Psychiatric Research and by the National Institutes of Health (grants U01MH105641, R01MH077139 and T32GM007753).

Adapted from a Broad Institute news release.

 

 

https://img.washingtonpost.com/wp-apps/imrs.php?src=https://img.washingtonpost.com/rf/image_908w/2010-2019/WashingtonPost/2011/09/27/Production/Sunday/SunBiz/Images/mental2b.jpg&w=1484

This post has been updated.

For the first time, scientists have pinned down a molecular process in the brain that helps to trigger schizophrenia. The researchers involved in the landmark study, which was published Wednesday in the journal Nature, say the discovery of this new genetic pathway probably reveals what goes wrong neurologically in a young person diagnosed with the devastating disorder.

The study marks a watershed moment, with the potential for early detection and new treatments that were unthinkable just a year ago, according to Steven Hyman, director of the Stanley Center for Psychiatric Research at the Broad Institute at MIT. Hyman, a former director of the National Institute of Mental Health, calls it “the most significant mechanistic study about schizophrenia ever.”

“I’m a crusty, old, curmudgeonly skeptic,” he said. “But I’m almost giddy about these findings.”

The researchers, chiefly from the Broad Institute, Harvard Medical School and Boston Children’s Hospital, found that a person’s risk of schizophrenia is dramatically increased if they inherit variants of a gene important to “synaptic pruning” — the healthy reduction during adolescence of brain cell connections that are no longer needed.

[Schizophrenic patients have different oral bacteria than non-mentally ill individuals]

In patients with schizophrenia, a variation in a single position in the DNA sequence marks too many synapses for removal and that pruning goes out of control. The result is an abnormal loss of gray matter.

The genes involved coat the neurons with “eat-me signals,” said study co-author Beth Stevens, a neuroscientist at Children’s Hospital and Broad. “They are tagging too many synapses. And they’re gobbled up.

The Institute’s founding director, Eric Lander, believes the research represents an astonishing breakthrough. “It’s taking what has been a black box…and letting us peek inside for the first time. And that is amazingly consequential,” he said.

The timeline for this discovery has been relatively fast. In July 2014, Broad researchers published the results of the largest genomic study on the disorder and found more than 100 genetic locations linked to schizophrenia. Based on that research, Harvard and Broad geneticist Steven McCarroll analyzed data from about 29,000 schizophrenia cases, 36,000 controls and 700 post mortem brains. The information was drawn from dozens of studies performed in 22 countries, all of which contribute to the worldwide database called the Psychiatric Genomics Consortium.

[Influential government-appointed panel recommends depression screening for everyone]

One area in particular, when graphed, showed the strongest association. It was dubbed the “Manhattan plot” for its resemblance to New York City’s towering buildings. The highest peak was on chromosome 6, where McCarroll’s team discovered the gene variant. C4 was “a dark corner of the human genome,” he said, an area difficult to decipher because of its “astonishing level” of diversity.

C4 and numerous other genes reside in a region of chromosome 6 involved in the immune system, which clears out pathogens and similar cellular debris from the brain. The study’s researchers found that one of C4’s variants, C4A, was most associated with a risk for schizophrenia.

More than 25 million people around the globe are affected by schizophrenia, according to the World Health Organization, including 2 million to 3 million Americans. Highly hereditable, it is one of the most severe mental illnesses, with an annual economic burden in this country of tens of billions of dollars.

“This paper is really exciting,” said Jacqueline Feldman, associate medical director of the National Alliance on Mental Illness. “We as scientists and physicians have to temper our enthusiasm because we’ve gone down this path before. But this is profoundly interesting.”

There have been hundreds of theories about schizophrenia over the years, but one of the enduring mysteries has been how three prominent findings related to each other: the apparent involvement of immune molecules, the disorder’s typical onset in late adolescence and early adulthood, and the thinning of gray matter seen in autopsies of patients.

[A low-tech way to help treat young schizophrenic patients]

“The thing about this result,” said McCarroll, the lead author, ” it makes a lot of other things understandable. To have a result to connect to these observations and to have a molecule and strong level of genetic evidence from tens of thousands of research participants, I think that combination sets [this study] apart.”

The authors stressed that their findings, which combine basic science with large-scale analysis of genetic studies, depended on an unusual level of cooperation among experts in genetics, molecular biology, developmental neurobiology and immunology.

“This could not have been done five years ago,” said Hyman. “This required the ability to reference a very large dataset . …When I was [NIMH] director, people really resisted collaborating. They were still in the Pharaoh era. They wanted to be buried with their data.”

The study offers a new approach to schizophrenia research, which has been largely stagnant for decades.  Most psychiatric drugs seek to interrupt psychotic thinking, but experts agree that psychosis is just a single symptom — and a late-occurring one at that. One of the chief difficulties for psychiatric researchers, setting them apart from most other medical investigators, is that they can’t cut schizophrenia out of the brain and look at it under a microscope. Nor are there any good animal models.

All that now has changed, according to Stevens. “We now have a strong molecular handle, a pathway and a gene, to develop better models,” he said.

Which isn’t to say a cure is right around the corner.

“This is the first exciting  clue, maybe even the most important we’ll ever have, but it will be decades” before a true cure is found,” Hyman said. “Hope is a wonderful thing. False promise is not.”

Insight Pharma Report

Three neurodegenerative disorders that are heavily focused on in this report include: Alzheimer’s Disease/Mild Cognitive Impairment, Parkinson’s Disease, and Amyotrophic Lateral Sclerosis. Part II of the report will include all three of these disorders, highlighting specifics including background, history, and development of the disease. Deeper into the chapters, the report will unfold biomarkers under investigation, genetic targets, and an analysis of multiple studies investigating these elements.

Experts interviewed in these chapters include:

  • Dr. Jens Wendland, Head of Neuroscience Genetics, Precision Medicine, Clinical Research, Pfizer Worldwide R&D
  • Dr. Howard J. Federoff, Executive Vice President for Health Sciences, Georgetown University
  • Dr. Andrew West, Associate Professor of Neurology and Neurobiology and Co-Director, Center for Neurodegeneration and Experimental Therapeutics
  • Dr. Merit Ester Cudkowicz, Chief of Neurology at Massachusetts General Hospital

Part III of the report makes a shift from neurobiomarkers to neurodiagnostics. This section highlights several diagnostics in play and in the making from a number of companies, identifying company strategies, research underway, hypotheses, and institution goals. Elite researchers and companies highlighted in this part include:

  • Dr. Xuemei Huang, Professor and Vice Chair, Department of Neurology; Professor of Neurosurgery, Radiology,  Pharmacology, and Kinesiology Director; Hershey Brain Analysis Research Laboratory for Neurodegenerative Disorders, Penn State University-Milton, S. Hershey Medical Center Department of Neurology
  • Dr. Andreas Jeromin, CSO and President of Atlantic Biomarkers
  • Julien Bradley, Senior Director, Sales & Marketing, Quanterix
  • Dr. Scott Marshall, Head of Bioanalytics, and Dr. Jared Kohler, Head of Biomarker Statistics, BioStat Solutions, Inc.

Further analysis appears in Part IV. This section includes a survey exclusively conducted for this report. With over 30 figures and graphics and an in depth analysis, this part features insight into targets under investigation, challenges, advantages, and desired features of future diagnostic applications. Furthermore, the survey covers more than just the featured neurodegenerative disorders in this report, expanding to Multiple Sclerosis and Huntington’s Disease.

Finally, Insight Pharma Reports concludes this report with clinical trial and pipeline data featuring targets and products from over 300 companies working in Alzheimer’s Disease, Parkinson’s Disease and Amyotrophic Lateral Sclerosis.

 

Epigenome Tapped to Understand Rise of Subtype of Brain Medulloblastoma

http://www.genengnews.com/gen-news-highlights/epigenome-tapped-to-understand-rise-of-subtype-of-brain-medulloblastoma/81252294/

Scientists have identified the cells that likely give rise to the brain tumor subtype Group 4 medulloblastoma. [V. Yakobchuk/ Fotolia]

http://www.genengnews.com/Media/images/GENHighlight/thumb_Jan_28_2016_Fotolia_6761569_ColorfulBrain_4412824411.jpg

An international team of scientists say they have identified the cells that likely give rise to the brain tumor subtype Group 4 medulloblastoma. The believe their study (“Active medulloblastoma enhancers reveal subgroup-specific cellular origins”), published in Nature, removes a barrier to developing more effective targeted therapies against the brain tumor’s most common subtype.

Medulloblastoma occurs in infants, children, and adults, but it is the most common malignant pediatric brain tumor. The disease includes four biologically and clinically distinct subtypes, of which Group 4 is the most common. In children, about half of medulloblastoma patients are of the Group 4 subtype. Efforts to improve patient outcomes, particularly for those with high-risk Group 4 medulloblastoma, have been hampered by the lack of accurate animal models.

Evidence from this study suggests Group 4 tumors begin in neural stem cells that are born in a region of the developing cerebellum called the upper rhomic lip (uRL), according to the researchers.

“Pinpointing the cell(s) of origin for Group 4 medulloblastoma will help us to better understand normal cerebellar development and dramatically improve our chances of developing genetically faithful preclinical mouse models. These models are desperately needed for learning more about Group 4 medulloblastoma biology and evaluating rational, molecularly targeted therapies to improve patient outcomes,” said Paul Northcott, Ph.D., an assistant member of the St. Jude department of developmental neurobiology. Dr. Northcott, Stefan Pfister, M.D., of the German Cancer Research Center (DKFZ), and James Bradner, M.D., of Dana-Farber Cancer Institute, are the corresponding authors.

The discovery and other findings about the missteps fueling tumor growth came from studying the epigenome. Researchers used the analytic tool ChiP-seq to identify and track medulloblastoma subtype differences based on the activity of epigenetic regulators, which included proteins known as master regulator transcription factors. They bind to DNA enhancers and super-enhancers. The master regulator transcription factors and super-enhancers work together to regulate the expression of critical genes, such as those responsible for cell identity.

Those and other tools helped investigators identify more than 3,000 super-enhancers in 28 medulloblastoma tumors as well as evidence that the activity of super-enhancers varied by subtype. The super-enhancers switched on known cancer genes, including genes like ALK, MYC, SMO, and OTX2 that are associated with medulloblastoma, the researchers reported.

Knowledge of the subtype super-enhancers led to identification of the transcription factors that regulate their activity. Using computational methods, researchers applied that information to reconstruct the transcription factor networks responsible for medulloblastoma subtype diversity and identity, providing previously unknown insights into the regulatory landscape and transcriptional output of the different medulloblastoma subtypes.

The approach helped to discover and nominate Lmx1A as a master regulator transcription factor of Group 4 tumors, which led to the identification of the likely Group 4 tumor cells of origin. Lmx1A was known to play an important role in normal development of cells in the uRL and cerebellum. Additional studies performed in mice with and without Lmx1A in this study supported uRL cells as the likely source of Group 4 tumors.

“By studying the epigenome, we also identified new pathways and molecular dependencies not apparent in previous gene expression and mutational studies,” explained Dr. Northcott. “The findings open new therapeutic avenues, particularly for the Group 3 and 4 subtypes where patient outcomes are inferior for the majority of affected children.”

For example, researchers identified increased enhancer activity targeting the TGFbeta pathway. The finding adds to evidence that the pathway may drive Group 3 medulloblastoma, currently the subtype with the worst prognosis. The pathway regulates cell growth, cell death, and other functions that are often disrupted in cancer, but it’s role in medulloblastoma is poorly understood.

The analysis included samples from 28 medulloblastoma tumors representing the four subtypes. Researchers believe it is the largest epigenetic study yet for any single cancer type and, importantly, the first to use a large cohort of primary patient tumor tissues instead of cell lines grown in the laboratory. Previous studies have suggested that cell lines may be of limited use for studying the tumor epigenome. The three Group 3 medulloblastoma cell lines used in this study reinforced the observation, highlighting significant differences in epigenetic regulators at work in medulloblastoma cell lines versus tumor samples.

 

 

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Kurzweill Reports in Medical Science I

Curator: Larry H. Bernstein, MD, FCAP

 

 

 

E-coli bacteria found in some China farms and patients cannot be killed with antiobiotic drug of last resort

“One of the most serious global threats to human health in the 21st century” — could spread around the world, requiring “urgent coordinated global action”
November 20, 2015

http://www.kurzweilai.net/e-coli-bacteria-found-in-some-china-farms-and-patients-cannot-be-killed-with-antiobiotic-drug-of-last-resort

Colistin antibiotic overused in farm animals in China apparently caused E-coli bacteria to become completely resistant to treatment; E-coli strain has already spread to Laos and Malaysia (credit: Yi-Yun Liu et al./Lancet Infect Dis)

Widespread E-coli bacteria that cannot be killed with the antiobiotic drug of last resort — colistin — have been found in samples taken from farm pigs, meat products, and a small number of patients in south China, including bacterial strains with epidemic potential, an international team of scientists revealed in a paper published Thursday Nov. 19 in the journal The Lancet Infectious Diseases.

The scientists in China, England, and the U.S. found a new gene, MCR-1, carried in E-coli bacteria strain SHP45. MCR-1 enables bacteria to be highly resistant to colistin and other polymyxins drugs.

“The emergence of the MCR-1 gene in China heralds a disturbing breach of the last group of antibiotics — polymixins — and an end to our last line of defense against infection,” said Professor Timothy Walsh, from the Cardiff University School of Medicine, who collaborated on this research with scientists from South China Agricultural University.

Walsh, an expert in antibiotic resistance, is best known for his discovery in 2011 of the NDM-1 disease-causing antibiotic-resistant superbug in New Delhi’s drinking water supply. “The rapid spread of similar antibiotic-resistant genes such as NDM-1 suggests that all antibiotics will soon be futile in the face of previously treatable gram-negative bacterial infections such as E.coli and salmonella,” he said.

Likely to spread worldwide; already found in Laos and Malaysia

The MCR-1 gene was found on plasmids — mobile DNA that can be easily copied and transferred between different bacteria, suggesting an alarming potential to spread and diversify between different bacterial populations.

Structure of plasmid pHNSHP45 carrying MCR-1 from Escherichia coli strain SHP45 (credit: Yi-Yun Liu et al./Lancet Infect Dis)

“We now have evidence to suggest that MCR-1-positive E.coli has spread beyond China, to Laos and Malaysia, which is deeply concerning,” said Walsh.  “The potential for MCR-1 to become a global issue will depend on the continued use of polymixin antibiotics, such as colistin, on animals, both in and outside China; the ability of MCR-1 to spread through human strains of E.coli; and the movement of people across China’s borders.”

“MCR-1 is likely to spread to the rest of the world at an alarming rate unless we take a globally coordinated approach to combat it. In the absence of new antibiotics against resistant gram-negative pathogens, the effect on human health posed by this new gene cannot be underestimated.”

“Of the top ten largest producers of colistin for veterinary use, one is Indian, one is Danish, and eight are Chinese,” The Lancet Infectious Diseases notes. “Asia (including China) makes up 73·1% of colistin production with 28·7% for export including to Europe.29 In 2015, the European Union and North America imported 480 tonnes and 700 tonnes, respectively, of colistin from China.”

Urgent need for coordinated global action

“Our findings highlight the urgent need for coordinated global action in the fight against extensively resistant and pan-resistant gram-negative bacteria,” the journal paper concludes.

“The implications of this finding are enormous,” an associated editorial comment to the The Lancet Infectious Diseases paper stated. “We must all reiterate these appeals and take them to the highest levels of government or face increasing numbers of patients for whom we will need to say, ‘Sorry, there is nothing I can do to cure your infection.’”

Margaret Chan, MD, Director-General of the World Health Organization, warned in 2011 that “the world is heading towards a post-antibiotic era, in which many common infections will no longer have a cure and, once again, kill unabated.”

“Although in its 2012 World Health Organization Advisory Group on Integrated Surveillance of Antimicrobial Resistance (AGISAR) report the WHO concluded that colistin should be listed under those antibiotics of critical importance, it is regrettable that in the 2014 Global Report on Surveillance, the WHO did not to list any colistin-resistant bacteria as part of their ‘selected bacteria of international concern,’” The Lancet Infectious Diseases paper says, reflecting WHO’s inaction in Ebola-stricken African countries, as noted last September by the international medical humanitarian organization Médecins Sans Frontières.

Funding for the E-coli bacteria study was provided by the Ministry of Science and Technology of China and National Natural Science Foundation of China.


Abstract of Emergence of plasmid-mediated colistin resistance mechanism MCR-1 in animals and human beings in China: a microbiological and molecular biological study

Until now, polymyxin resistance has involved chromosomal mutations but has never been reported via
horizontal gene transfer. During a routine surveillance project on antimicrobial resistance in commensal Escherichia coli from food animals in China, a major increase of colistin resistance was observed. When an E coli strain, SHP45, possessing colistin resistance that could be transferred to another strain, was isolated from a pig, we conducted further analysis of possible plasmid-mediated polymyxin resistance. Herein, we report the emergence of the first plasmid-mediated polymyxin resistance mechanism, MCR-1, in Enterobacteriaceae.

The mcr-1 gene in E coli strain SHP45 was identified by whole plasmid sequencing and subcloning. MCR-1 mechanistic studies were done with sequence comparisons, homology modelling, and electrospray ionisation mass spectrometry. The prevalence of mcr-1 was investigated in E coli and Klebsiella pneumoniae strains collected from five provinces between April, 2011, and November, 2014. The ability of MCR-1 to confer polymyxin resistance in vivo was examined in a murine thigh model.

Polymyxin resistance was shown to be singularly due to the plasmid-mediated mcr-1 gene. The plasmid carrying mcr-1 was mobilised to an E coli recipient at a frequency of 10−1 to 10−3 cells per recipient cell by conjugation, and maintained in K pneumoniae and Pseudomonas aeruginosa. In an in-vivo model, production of MCR-1 negated the efficacy of colistin. MCR-1 is a member of the phosphoethanolamine transferase enzyme family, with expression in E coli resulting in the addition of phosphoethanolamine to lipid A. We observed mcr-1 carriage in E coli isolates collected from 78 (15%) of 523 samples of raw meat and 166 (21%) of 804 animals during 2011–14, and 16 (1%) of 1322 samples from inpatients with infection.

The emergence of MCR-1 heralds the breach of the last group of antibiotics, polymyxins, by plasmid-mediated resistance. Although currently confined to China, MCR-1 is likely to emulate other global resistance mechanisms such as NDM-1. Our findings emphasise the urgent need for coordinated global action in the fight against pan-drug-resistant Gram-negative bacteria.

 

Researchers discover signaling molecule that helps neurons find their way in the developing brain

November 20, 2015

http://www.kurzweilai.net/researchers-discover-signaling-molecule-that-helps-neurons-find-their-way-in-the-developing-brain

This image shows a section of the spinal cord of a mouse embryo. Neurons appear green. Commissural axons (which connect the two sides of the brain) appear as long, u-shaped threads, and the bottom, yellow segment of the structure represents the midline (between brain hemispheres). (credit: Laboratory of Brain Development and Repair/ The Rockefeller University)

Rockefeller University researchers have discovered a molecule secreted by cells in the spinal cord that helps guide axons (neuron extensions) during a critical stage of central nervous system development in the embryo. The finding helps solve the mystery: how do the billions of neurons in the embryo nimbly reposition themselves within the brain and spinal cord, and connect branches to form neural circuits?

Working in mice, the researchers identified an axon guidance factor, NELL2, and explained how it makes commissural axons (which connect the two sides of the brain).

The findings could help scientists understand what goes wrong in a rare disease called horizontal gaze palsy with progressive scoliosis. People affected by the condition often suffer from abnormal spine curvature, and are unable to move their eyes horizontally from side to side. The study was published Thursday Nov. 19 in the journal Science.


Abstract of Operational redundancy in axon guidance through the multifunctional receptor Robo3 and its ligand NELL2

Axon pathfinding is orchestrated by numerous guidance cues, including Slits and their Robo receptors, but it remains unclear how information from multiple cues is integrated or filtered. Robo3, a Robo family member, allows commissural axons to reach and cross the spinal cord midline by antagonizing Robo1/2–mediated repulsion from midline-expressed Slits and potentiating deleted in colorectal cancer (DCC)–mediated midline attraction to Netrin-1, but without binding either Slits or Netrins. We identified a secreted Robo3 ligand, neural epidermal growth factor-like-like 2 (NELL2), which repels mouse commissural axons through Robo3 and helps steer them to the midline. These findings identify NELL2 as an axon guidance cue and establish Robo3 as a multifunctional regulator of pathfinding that simultaneously mediates NELL2 repulsion, inhibits Slit repulsion, and facilitates Netrin attraction to achieve a common guidance purpose.

A sensory illusion that makes yeast cells self-destruct

A possible tactic for cancer therapeutics
November 20, 2015

http://www.kurzweilai.net/a-sensory-illusion-that-makes-yeast-cells-self-destruct

 

Effects of osmotic changes on yeast cell growth. (A) Schematic of the flow chamber used to create osmotic level oscillations for different periods of time. (B) Cell growth for these periods. The graphs show the average number of progeny cells (blue) before and after applying stress for different periods (gray shows orginal “no stress” line). The inset shows representative images of cells for two periods. (credit: Amir Mitchell et al./Science)

UC San Francisco researchers have discovered that even brainless single-celled yeast have “sensory biases” that can be hacked by a carefully engineered illusion — a finding that could be used to develop new approaches to fighting diseases such as cancer.

In the new study, published online Thursday November 19 in Science Express, Wendell Lim, PhD, the study’s senior author*, and his team discovered that yeast cells falsely perceive a pattern of osmotic levels (by applying potassium chloride) that alternate in eight minute intervals as massive, continuously increasing stress. In response, the microbes over-respond and kill themselves. (In their natural environment, salt stress normally gradually increases.)

The results, Lim says, suggest a whole new way of looking at the perceptual abilities of simple cells and this power of illusion could even be used to develop new approaches to fighting cancer and other diseases.

“Our results may also be relevant for cellular signaling in disease, as mutations affecting cellular signaling are common in cancer, autoimmune disease, and diabetes,” the researchers conclude in the paper. “These mutations may rewire the native network, and thus could modify its activation and adaptation dynamics. Such network rewiring in disease may lead to changes that can be most clearly revealed by simulation with oscillatory inputs or other ‘non-natural’ patterns.

“The changes in network response behaviors could be exploited for diagnosis and functional profiling of disease cells, or potentially taken advantage of as an Achilles’ heel to selectively target cells bearing the diseased network.”

https://youtu.be/CuDjZrM8xtA
UC San Francisco (UCSF) | Sensory Illusion Causes Cells to Self-Destruct

* Chair of the Department of Cellular and Molecular Pharmacology at UCSF, director of the UCSF Center for Systems and Synthetic Biology, and a Howard Hughes Medical Institute (HHMI) investigator.

** Normally, sensor molecules in a yeast cell detect changes in salt concentration and instruct the cell to respond by producing a protective chemical. The researchers found that the cells were perfectly capable of adapting when they flipped the salt stress on and off every minute or every 32 minutes. But to their surprise, when they tried an eight-minute oscillation of precisely the same salt level the cells quickly stopped growing and began to die off.


Abstract of Oscillatory stress stimulation uncovers an Achilles’ heel of the yeast MAPK signaling network

Cells must interpret environmental information that often changes over time. We systematically monitored growth of yeast cells under various frequencies of oscillating osmotic stress. Growth was severely inhibited at a particular resonance frequency, at which cells show hyperactivated transcriptional stress responses. This behavior represents a sensory misperception—the cells incorrectly interpret oscillations as a staircase of ever-increasing osmolarity. The misperception results from the capacity of the osmolarity-sensing kinase network to retrigger with sequential osmotic stresses. Although this feature is critical for coping with natural challenges—like continually increasing osmolarity—it results in a tradeoff of fragility to non-natural oscillatory inputs that match the retriggering time. These findings demonstrate the value of non-natural dynamic perturbations in exposing hidden sensitivities of cellular regulatory networks.

Google Glass helps cardiologists complete difficult coronary artery blockage surgery

November 20, 2015

http://www.kurzweilai.net/google-glass-helps-cardiologists-in-challenging-coronary-artery-blockage-surgery

 

Google Glass allowed the surgeons to clearly visualize the distal coronary vessel and verify the direction of the guide wire advancement relative to the course of the occluded vessel segment. (credit: Maksymilian P. Opolski et al./Canadian Journal of Cardiology

Cardiologists from the Institute of Cardiology, Warsaw, Poland have used Google Glass in a challenging surgical procedure, successfully clearing a blockage in the right coronary artery of a 49-year-old male patient and restoring blood flow, reports the Canadian Journal of Cardiology.

Chronic total occlusion, a complete blockage of the coronary artery, sometimes referred to as the “final frontier in interventional cardiology,” represents a major challenge for catheter-based percutaneous coronary intervention (PCI), according to the cardiologists.

That’s because of the difficulty of recanalizing (forming new blood vessels through an obstruction) combined with poor visualization of the occluded coronary arteries.

Coronary computed tomography angiography (CTA) is increasingly used to provide physicians with guidance when performing PCI for this procedure. The 3-D CTA data can be projected on monitors, but this technique is expensive and technically difficult, the cardiologists say.

So a team of physicists from the Interdisciplinary Centre for Mathematical and Computational Modelling of theUniversity of Warsaw developed a way to use Google Glass to clearly visualize the distal coronary vessel and verify the direction of the guide-wire advancement relative to the course of the blocked vessel segment.

Three-dimensional reconstructions displayed on Google Glass revealed the exact trajectory of the distal right coronary artery (credit: Maksymilian P. Opolski et al./Canadian Journal of Cardiology)

The procedure was completed successfully, including implantation of two drug-eluting stents.

“This case demonstrates the novel application of wearable devices for display of CTA data sets in the catheterization laboratory that can be used for better planning and guidance of interventional procedures, and provides proof of concept that wearable devices can improve operator comfort and procedure efficiency in interventional cardiology,” said lead investigatorMaksymilian P. Opolski, MD, PhD, of the Department of Interventional Cardiology and Angiology at the Institute of Cardiology, Warsaw, Poland.

“We believe wearable computers have a great potential to optimize percutaneous revascularization, and thus favorably affect interventional cardiologists in their daily clinical activities,” he said. He also advised that “wearable devices might be potentially equipped with filter lenses that provide protection against X-radiation.


Abstract of First-in-Man Computed Tomography-Guided Percutaneous Revascularization of Coronary Chronic Total Occlusion Using a Wearable Computer: Proof of Concept

We report a case of successful computed tomography-guided percutaneous revascularization of a chronically occluded right coronary artery using a wearable, hands-free computer with a head-mounted display worn by interventional cardiologists in the catheterization laboratory. The projection of 3-dimensional computed tomographic reconstructions onto the screen of virtual reality glass allowed the operators to clearly visualize the distal coronary vessel, and verify the direction of the guide wire advancement relative to the course of the occluded vessel segment. This case provides proof of concept that wearable computers can improve operator comfort and procedure efficiency in interventional cardiology.

Modulating brain’s stress circuity might prevent Alzheimer’s disease

Drug significantly prevented onset of cognitive and cellular effects in mice
November 17, 2015

http://www.kurzweilai.net/modulating-brains-stress-circuity-might-prevent-alzheimers-disease

 

Effect of drug treatment on AD mice in control group (left) or drug (right) on Ab plaque load. (credit: Cheng Zhang et al./Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association)

In a novel animal study design that mimicked human clinical trials, researchers at University of California, San Diego School of Medicine report that long-term treatment using a small-molecule drug that reduces activity of  the brain’s stress circuitry significantly reduces Alzheimer’s disease (AD) neuropathology and prevents onset of cognitive impairment in a mouse model of the neurodegenerative condition.

The findings are described in the current online issue of the journal Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.

Previous research has shown a link between the brain’s stress signaling pathways and AD. Specifically, the release of a stress-coping hormone called corticotropin-releasing factor (CRF), which is widely found in the brain and acts as a neurotransmitter/neuromodulator, is dysregulated in AD and is associated with impaired cognition and with detrimental changes in tau protein and increased production of amyloid-beta protein fragments that clump together and trigger the neurodegeneration characteristic of AD.

“Our work and that of our colleagues on stress and CRF have been mechanistically implicated in Alzheimer’s disease, but agents that impact CRF signaling have not been carefully tested for therapeutic efficacy or long-term safety in animal models,” said the study’s principal investigator and corresponding author Robert Rissman, PhD, assistant professor in the Department of Neurosciences and Biomarker Core Director for the Alzheimer’s Disease Cooperative Study (ADCS).

The researchers determined that modulating the mouse brain’s stress circuitry mitigated generation and accumulation of amyloid plaques widely attributed with causing neuronal damage and death. As a consequence, behavioral indicators of AD were prevented and cellular damage was reduced.  The mice began treatment at 30-days-old — before any pathological or cognitive signs of AD were present — and continued until six months of age.

One particular challenge, Rissman noted, is limiting exposure of the drug to the brain so that it does not impact the body’s ability to respond to stress. “This can be accomplished because one advantage of these types of small molecule drugs is that they readily cross the blood-brain barrier and actually prefer to act in the brain,” Rissman said.

“Rissman’s prior work demonstrated that CRF and its receptors are integrally involved in changes in another AD hallmark, tau phosphorylation,” said William Mobley, MD, PhD, chair of the Department of Neurosciences and interim co-director of the Alzheimer’s Disease Cooperative Study at UC San Diego. “This new study extends those original mechanistic findings to the amyloid pathway and preservation of cellular and synaptic connections.  Work like this is an excellent example of UC San Diego’s bench-to-bedside legacy, whereby we can quickly move our basic science findings into the clinic for testing,” said Mobley.

Rissman said R121919 was well-tolerated by AD mice (no significant adverse effects) and deemed safe, suggesting CRF-antagonism is a viable, disease-modifying therapy for AD. Drugs like R121919 were originally designed to treat generalized anxiety disorder, irritable bowel syndrome and other diseases, but failed to be effective in treating those disorders.

Rissman noted that repurposing R121919 for human use was likely not possible at this point. He and colleagues are collaborating with the Sanford Burnham Prebys Medical Discovery Institute to design new assays to discover the next generation of CRF receptor-1 antagonists for testing in early phase human safety trials.

“More work remains to be done, but this is the kind of basic research that is fundamental to ultimately finding a way to cure — or even prevent —Alzheimer’s disease,” said David Brenner, MD, vice chancellor, UC San Diego Health Sciences and dean of UC San Diego School of Medicine. “These findings by Dr. Rissman and his colleagues at UC San Diego and at collaborating institutions on the Mesa suggest we are on the cusp of creating truly effective therapies.”


Abstract of Corticotropin-releasing factor receptor-1 antagonism mitigates beta amyloid pathology and cognitive and synaptic deficits in a mouse model of Alzheimer’s disease

Introduction: Stress and corticotropin-releasing factor (CRF) have been implicated as mechanistically involved in Alzheimer’s disease (AD), but agents that impact CRF signaling have not been carefully tested for therapeutic efficacy or long-term safety in animal models.

Methods: To test whether antagonism of the type-1 corticotropin-releasing factor receptor (CRFR1) could be used as a disease-modifying treatment for AD, we used a preclinical prevention paradigm and treated 30-day-old AD transgenic mice with the small-molecule, CRFR1-selective antagonist, R121919, for 5 months, and examined AD pathologic and behavioral end points.

Results: R121919 significantly prevented the onset of cognitive impairment in female mice and reduced cellular and synaptic deficits and beta amyloid and C-terminal fragment-β levels in both genders. We observed no tolerability or toxicity issues in mice treated with R121919.

Discussion: CRFR1 antagonism presents a viable disease-modifying therapy for AD, recommending its advancement to early-phase human safety trials.

Allen Institute researchers decode patterns that make our brains human
Conserved gene patterning across human brains provide insights into health and disease
November 17, 2015

http://www.kurzweilai.net/allen-institute-researchers-decode-patterns-that-make-our-brains-human

 

Percentage of known neuron-, astrocyte- and oligodendrocyte-enriched genes in 32 modules, ordered by proportion of neuron-enriched gene membership. (credit: Michael Hawrylycz et al./Nature Neuroscience)

Allen Institute researchers have identified a surprisingly small set of just 32 gene-expression patterns for all 20,000 genes across 132 functionally distinct human brain regions, and these patterns appear to be common to all individuals.

In research published this month in Nature Neuroscience, the researchers used data for six brains from the publicly available Allen Human Brain Atlas. They believe the study is important because it could provide a baseline from which deviations in individuals may be measured and associated with diseases, and could also provide key insights into the core of the genetic code that makes our brains distinctly human.

While many of these patterns were similar in human and mouse, many genes showed different patterns in human. Surprisingly, genes associated with neurons were most conserved (consistent) across species, while those for the supporting glial cells showed larger differences. The most highly stable genes (the genes that were most consistent across all brains) include those associated with diseases and disorders like autism and Alzheimer’s, and these genes include many existing drug targets.

These patterns provide insights into what makes the human brain distinct and raise new opportunities to target therapeutics for treating disease.

The researchers also found that the pattern of gene expression in cerebral cortex is correlated with “functional connectivity” as revealed by neuroimaging data from the Human Connectome Project.

“The human brain is phenomenally complex, so it is quite surprising that a small number of patterns can explain most of the gene variability across the brain,” says Christof Koch, Ph.D., President and Chief Scientific Officer at the Allen Institute for Brain Science. “There could easily have been thousands of patterns, or none at all. This gives us an exciting way to look further at the functional activity that underlies the uniquely human brain.”


Abstract of Canonical genetic signatures of the adult human brain

The structure and function of the human brain are highly stereotyped, implying a conserved molecular program responsible for its development, cellular structure and function. We applied a correlation-based metric called differential stability to assess reproducibility of gene expression patterning across 132 structures in six individual brains, revealing mesoscale genetic organization. The genes with the highest differential stability are highly biologically relevant, with enrichment for brain-related annotations, disease associations, drug targets and literature citations. Using genes with high differential stability, we identified 32 anatomically diverse and reproducible gene expression signatures, which represent distinct cell types, intracellular components and/or associations with neurodevelopmental and neurodegenerative disorders. Genes in neuron-associated compared to non-neuronal networks showed higher preservation between human and mouse; however, many diversely patterned genes displayed marked shifts in regulation between species. Finally, highly consistent transcriptional architecture in neocortex is correlated with resting state functional connectivity, suggesting a link between conserved gene expression and functionally relevant circuitry.

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Brain Development

Larry H. Bernstein, MD, FCAP, Curator

LPBI

Updated 11/22/2015

Single Gene Found to Play Huge Role in Brain Development

http://www.genengnews.com/gen-news-highlights/single-gene-found-to-play-huge-role-in-brain-development/81251997/

 

Single Gene Found to Play Huge Role in Brain Development

Figure 1: Cells in which NeuroD1 is turned on are reprogrammed to become neurons. Cell nuclei are shown in blue (Höchst stain) and neurons are shown in red (stained with neuronal marker TUJ1). [A. Pataskar,J. Jung, V. Tiwari]

 

Researchers at the Institute of Molecular Biology (IMB) in Mainz, Germany say they have unraveled a complex regulatory mechanism that explains how a single gene can drive the formation of brain cells. Their study (“NeuroD1 reprograms chromatin and transcription factor landscapes to induce the neuronal program”), published in The EMBO Journal, is an important step toward a better understanding of how the brain develops. It also harbors potential for regenerative medicine, according to the scientists.

Neurodegenerative disorders, such as Parkinson’s disease, are often characterized by an irreversible loss neurons. Unlike many other cell types in the body, neurons are generally not able to regenerate by themselves, so if the brain is damaged, it stays damaged. One hope of developing treatments for this kind of damage is to understand how the brain develops in the first place, and then try to imitate the process. However, the brain is also one of the most complex organs in the body, and very little is understood about the molecular pathways that guide its development.

 

Figure 2: Diagram showing how NeuroD1 influences the development of neurons. During brain development, expression of NeuroD1 marks the onset of neurogenesis. NeuroD1 accomplishes this via epigenetic reprogramming: neuronal genes are switched on, and the cells develop into neurons. TF: transcription factor; V: ventricle; P: pial surface. [A. Pataskar, J. Jung, V. Tiwari]

 

ijay Tiwari, Ph.D, and his group have been investigating a central gene in brain development, NeuroD1. This gene is expressed in the developing brain and marks the onset of neurogenesis.

In their research article, Dr. Tiwari and his colleagues have shown that during brain development NeuroD1 is not only expressed in brain stem cells but acts as a master regulator of a large number of genes that cause these cells to develop into neurons. They used a combination of neurobiology, epigenetics, and computational biology approaches to show that these genes are normally turned off in development, but NeuroD1 activity changes their epigenetic state in order to turn them on. Strikingly, the researchers show that these genes remain switched on even after NeuroD1 is later switched off. They further show that this is because NeuroD1 activity leaves permanent epigenetic marks on these genes that keep them turned on, in other words it creates an epigenetic memory of neuronal differentiation in the cell.

“Our research has shown how a single factor, NeuroD1, has the capacity to change the epigenetic landscape of the cell, resulting in a gene expression program that directs the generation of neurons,” wrote the screenplay investigators.

“This is a significant step toward understanding the relationship between DNA sequence, epigenetic changes and cell fate. It not only sheds new light on the formation of the brain during embryonic development but also opens up novel avenues for regenerative therapy,” says Dr. Tiwari.

 

NEUROD1 neuronal differentiation 1 [ Homo sapiens (human) ]

Official Symbol NEUROD1 provided by HGNC 

Official Full Name neuronal differentiation 1 provided by HGNC

Primary source HGNC:HGNC:7762 See related Ensembl:ENSG00000162992; HPRD:03428; MIM:601724; Vega:OTTHUMG00000132583

Gene type protein coding

RefSeq status REVIEWED

OrganismHomo sapiens

Lineage Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi; Mammalia; Eutheria; Euarchontoglires; Primates; Haplorrhini; Catarrhini; Hominidae; Homo

Also known asBETA2; BHF-1; MODY6; NEUROD; bHLHa3

Summary This gene encodes a member of the NeuroD family of basic helix-loop-helix (bHLH) transcription factors. The protein forms heterodimers with other bHLH proteins and activates transcription of genes that contain a specific DNA sequence known as the E-box. It regulates expression of the insulin gene, and mutations in this gene result in type II diabetes mellitus. [provided by RefSeq, Jul 2008]

Orthologs mouse all

 

https://en.wikipedia.org/wiki/NEUROD1

Neurogenic differentiation 1 (NeuroD1), also called β2,[1] is a transcription factor of the NeuroD-type. It is encoded by the human gene NEUROD1.

It is a member of the NeuroD family of basic helix-loop-helix (bHLH) transcription factors. The protein forms heterodimers with other bHLH proteins and activates transcription of genes that contain a specific DNA sequence known as the E-box. It regulates expression of the insulin gene, and mutations in this gene result in type II diabetes mellitus.[2]

Contents  [hide

1Interactions

2References

3Further reading

4External links

 

NeuroD1 induces terminal neuronal differentiation in olfactory neurogenesis

Camille BoutinOlaf HardtAntoine de ChevignyNathalie CoréSandra GoebbelsRalph SeidenfadenAndreas Bosio and Harold Cremer

PNAS Jan 19, 2010; 107(3):   1201–1206.   http://dx.doi.org:/10.1073/pnas.0909015107

After their generation and specification in periventricular regions, neuronal precursors maintain an immature and migratory state until their arrival in the respective target structures. Only here are terminal differentiation and synaptic integration induced. Although the molecular control of neuronal specification has started to be elucidated, little is known about the factors that control the latest maturation steps. We aimed at identifying factors that induce terminal differentiation during postnatal and adult neurogenesis, thereby focusing on the generation of periglomerular interneurons in the olfactory bulb. We isolated neuronal precursors and mature neurons from the periglomerular neuron lineage and analyzed their gene expression by microarray. We found that expression of the bHLH transcription factor NeuroD1 strikingly coincides with terminal differentiation. Using brain electroporation, we show that overexpression of NeuroD1 in the periventricular region in vivo leads to the rapid appearance of cells with morphological and molecular characteristics of mature neurons in the subventricular zone and rostral migratory stream. Conversely, shRNA-induced knockdown of NeuroD1 inhibits terminal neuronal differentiation. Thus, expression of a single transcription factor is sufficient to induce neuronal differentiation of neural progenitors in regions that normally do not show addition of new neurons. These results suggest a considerable potential of NeuroD1 for use in cell-therapeutic approaches in the nervous system.

 

Determination of neuronal subtypes is an early event that coincides with cell cycle exit (1, 2). However, after their generation, new neurons have to remain immature for prolonged periods, allowing their migration to final destinations where terminal differentiation occurs (3). Little is known about the factors that maintain the precursor state or induce terminal differentiation.

Olfactory neurogenesis is particularly suited to approach these late steps in neuronal differentiation. Here, stem cell populations first located in the ventricular zone and after the establishment of an ependymal layer positioned in subventricular zone (SVZ) generate migratory neuroblasts throughout life (4). These perform long-distance chain migration via the rostral migratory stream (RMS) into the olfactory bulb (OB), where they migrate into the granule cell layer (GCL) and the glomerular layer (GL) to differentiate into GABA- and dopaminergic neurons (4, 5). Thus, in this system, generation of neurons is permanent and the consecutive steps in the neurogenic sequence are spatially separated.

Determination of newly generated neurons has been studied intensively over the past years. For example, it has been demonstrated that defined areas surrounding the lateral ventricle contain predetermined stem cells that give rise to defined subsets of interneurons (6, 7). Several transcription factors have been implicated in the specification of the different neuronal populations. The zinc finger transcription factor sp8, for instance, appears to be involved in the generation of interneurons expressing calretinin (8), and analysis of Sall3 mutant mice (9) points to a role of this factor in the dopaminergic, tyrosine hydroxylase–positive lineage (10). Furthermore, it appears that interneuron diversity relies on the combinatorial expression of such transcription factors. This is exemplified by Pax6 and Dlx2, which have been shown to interact in the determination of adult generated neuronal precursors toward a dopaminergic fate (9, 11, 12). All of these transcriptional regulators are expressed early during the neurogenic process and remain present until terminal differentiation occurs.

We aimed at the identification of transcription factors that induce terminal differentiation of postnatal generated neurons in the OB. To do so we isolated neuronal precursors and differentiated interneurons from the periglomerular lineage of the OB and compared their gene expression by microarray. We established that the expression of NeuroD1, a bHLH transcription factor that has been implicated in neuronal differentiation in several experimental systems (1317), coincides with the passage from neuronal precursor to mature interneurons. Functionally, we show that premature expression of NeuroD1 in vitro and in vivo induced highly efficiently the differentiation of forebrain progenitors. In vivo, this leads to the transitory appearance of ectopic neurons in the SVZ, RMS and striatum. Conversely, knockdown of NeuroD1 specifically inhibits terminal maturation of periglomerular neurons in the OB. Thus, NeuroD1 is both necessary and sufficient to induce key steps in terminal neuronal differentiation.

 

NeuroD1 Is Specifically Expressed in Mature GL Interneurons.

Subpopulations of neuronal precursors destined for the GCL and GL of the OB are generated by regionally defined stem cell populations in the periventricular region but migrate intermingled in the RMS to the OB. Once there, cells resegregate: granule cell precursors terminate their migration in the GCL, whereas the smaller population of periglomerular neuron precursors traverses this layer and the mitral cell layer (MCL) to invade the peripherally located GL (Fig. 1A). Thus, at a given time point, the GL contains both mature periglomerular neurons and their specific progenitors. Based on this spatial organization we isolated these two populations, concurrently depleting glial cells.

We devised a three-step strategy based on the following: (i) microdissection followed by enzymatic dissociation of the postnatal GL, (ii) depletion of contaminating glial cells by magnetic activated cell sorting (MACS) using an A2B5 specific antibody (18), (iii) separation of PSA-NCAM expressing cells (19) from the remaining fraction containing the mature neurons (Fig. 1B). The same purification strategy was applied to tissue microdissected from the P2 periventricular region (18). Characterization of the different cell population after sorting was performed via immunocytochemistry using the markers used for sorting (A2B5 and PSA-NCAM) as well as the differentiation marker Gad65 (18) (Fig. S1). Thus, as starting material we obtained highly enriched mature OB periglomerular interneurons (PGN), their immature progenitors (PGP), as well as a mixed population of generic progenitors (GP) from the SVZ/RMS.

 

Fig. 1.

Fig. 1.

Expression of NeuroD1 in the olfactory neurogenic system (A) DAPI-stained coronal section through the olfactory bulb of P5. (B) Strategy to isolate neuronal populations at different steps of their maturation. (C) Relative changes in gene expression for selected genes. Expression in GP was considered baseline, and changes are expressed as fold difference. (D–F) NeuroD1 in situ hybridization on sections from P5 mouse brain. No signal was detected along the lateral ventricle or in the RMS (D). In the olfactory bulb, individual NeuroD1+ cells were present in the GCL, whereas the MCL and the GL contained higher amounts (E, high magnification in F). A similar expression pattern was found after β-gal reaction on NeuroD1-lacZ-knockin tissue (G). (Scale bar: 200 μm in A; 100 μm inD and E; 20 μm in F and G).

 

Based on the purified and characterized cell populations, we performed microarray analyses to gain insight into the changes in gene expression during the neurogenic process. Investigation of expression dynamics of genes associated with either the precursor status or neuronal differentiation (Fig. S2 A and B) were used to validate the approach. Furthermore, these data were compared with those from an already available Serial Analysis of Gene Expression (SAGE) study (20).

Serial Analysis of Microarray (SAM) demonstrated the presence of groups of genes with comparable expression patterns (Fig. S2 C–E). Interestingly, only a relatively small fraction of genes were absent in the immature cell populations GP and PGP but highly represented in mature PGN (Fig. S2E). One of the genes showing such a pattern was NeuroD1, which was expressed more than 50-fold higher in PGN than in the immature populations (Fig. 1C). This was in agreement with the above-cited SAGE data, showing that NeuroD1 expression was below the detection level in neuronal precursors of the adult SVZ (20). Thus, expression of NeuroD1 was absent from precursors but coincided with terminal neuronal differentiation.

This late expression of NeuroD1 was in contrast to that of factors that have been functionally implicated in the specification of PGN, including Pax6, Sp8 and Sall3, which were expressed in both the immature populations and in the mature neurons (Fig. 1C; in situ hybridization for Pax6 in Fig. S3). Only Dlx2 showed a moderate increase in the PGN lineage outgoing, however, from an already considerable baseline level in migrating precursors (12) (Fig. 1C).

Next we analyzed the expression of NeuroD1 using in situ hybridization on P5 forebrain sections. Strong expression was found in the GL, whereas weaker expression was observed in the GCL and MCL (Fig. 1 Eand F). The transcript was undetectable in the periventricular region and the RMS (Fig. 1D). This staining was confirmed using NeuroD1-lacZ knockin mice (21) (Fig. 1G). In conclusion, these data demonstrated the absence of NeuroD1 from immature cells of the system and its strong expression in mature PGN. This pattern was coherent with a function in terminal neuronal differentiation.

NeuroD1 Induces Neuronal Differentiation in Vitro.

We studied the neurogenic potential of NeuroD1 in primary cultured neural stem cells using the neurosphere assay. In parallel to NeuroD1, we performed all experiments under the same conditions using the transcription factor Pax6, a well-described neurogenic signal in the system (9, 11, 12), to control for specificity of the observed effects. Neurosphere cells were coelectroporated with NeuroD1 or Pax6 expression vectors and GFP immediately before plating in differentiation conditions. One week after transfection, in the control condition, 14 ± 1% of the GFP-positive cells coexpressed the early neuronal marker Tuj1 (Fig. S4 A and D) whereas NeuroD1 induced Tuj1 expression in virtually all cells (98.0 ± 2%, Fig. S4 B and D). Pax6 gain-of-function led to an intermediate value (60.0 ± 3%, Fig. S4 C and D). NeuN, a later neuronal marker (22), was expressed by 21.1 ± 1% of the Tuj1-positive cells in the control situation (Fig. S4 E and H) but induced by NeuroD1 in almost all cells (93.9 ± 2%; Fig. S4 F and H). Surprisingly, Pax6 expression led to nearly complete disappearance of NeuN (1.7 ± 0.3%; Fig. S4 G and H). We investigated the induction of subtype specific markers by NeuroD1. Whereas tyrosine hydroxylase showed no augmentation, we found a 20% increase in calretinin labeling, in agreement with previous findings (23).

Next we investigated morphological parameters like process length as well as density and length of filopodia. Both NeuroD1 and Pax6 induced a significant, greater than 2-fold increase in process length (Fig. S4 I and L). We analyzed dendritic filopodia, structures that are believed to be precursors of dendritic spines (24). Expression of NeuroD1 induced a doubling in density and length of filopodia (Fig. S4 N, P, and Q). Interestingly, Pax6 reduced filopodia density to a level significantly below that of controls (Fig. S4 O and P), whereas length of the few remaining filopodia was not affected (7.0 ± 0.4 μm; Fig. S4Q).

Thus, the expression of NeuroD1 in neurosphere amplified neural stem cells induced neuronal commitment as well as morphological characteristics of mature neurons. Like NeuroD1, Pax6 favored neuronal commitment but appeared to actively suppress certain characteristics of terminal neuronal differentiation.

NeuroD1 Induces Ectopic Neurons in Vivo.

We asked whether NeuroD1 was also sufficient to induce neuronal differentiation in vivo. We used postnatal forebrain electroporation, an approach that allows efficient genetic manipulation of neural stem cells along the lateral ventricles and, consequently, of all transitory or permanent cell populations that are generated in the olfactory neurogenic process (25). The NeuroD1 expression vector or empty control plasmids were coelectroporated together with a GFP-containing vector that allowed visualization of transfected cells and their progeny at high resolution. Consequences of NeuroD1 gain-of-function were analyzed at 2, 4, 6, 8, and 15 days postelectroporation (dpe). As for the in vitro studies, results were compared with the effects of Pax6 gain-of-function.

At 2 dpe of a control vector into the lateral wall of the forebrain ventricle, 9.8 ± 1.3% (Fig. 2 A and K) of the GFP-expressing cells were localized in the VZ and had the morphology of radial glia (RG) (25). The majority of the GFP + cells, representing mainly neuronal precursors, were localized in the SVZ. Electroporation of a NeuroD1 expression vector induced a loss of GFP-positive RG cells (3.7 ± 0.5%; Fig. 2 B and K). The remaining cells in the VZ showed lower GFP levels than in controls (Fig. 2 A and B asterisks).

Fig. 2.

Fig. 2.

NeuroD1 induces neuronal morphology in vivo. Effect of NeuroD1 gain-of-function at different time points postelectroporation. (A and B) Coronal forebrain sections at the level of the lateral ventricle at 2 dpe. In the control condition, strongly GFP labeled RG are present in the VZ (A, asterisk). Expression of NeuroD1 induced a relative loss of radial glia and fainter GFP label (B, asterisk). (C and D) Coronal sections at the level of the lateral ventricle at 4 dpe. NeuroD1 expression induced an accumulation of transfected cells in the SVZ (D) and the almost total disappearance of radial glia (D). (E–F′) Sagittal sections of the RMS at 4 dpe. In the control situation, cells migrated toward the OB and presented the bipolar morphology specific of migrating precursors (E, E′, arrowheads). NeuroD1 electroporation induced loss of tangential orientation, induction of complex branching (F, F′, arrowhead), and invasion of the surrounding tissues (F, arrowheads). (G and H) Coronal section at the level of the olfactory bulb at 4 dpe. Although the majority of cells have reached the OB in the control situation (G), only a few cells were located in the center of the OB in the presence of NeuroD1 (H). (I and I′) Examples of cells presenting neuronal morphology in the SVZ at 4 dpe. (J) High magnification showing the presence of filopodia covering NeuroD1-expressing cells (arrowheads). (K) Quantification of GFP-positive cells presenting radial glia cell morphology along the lateral ventricle at 2 and 4 dpe. Control: 9.8 ± 1.3% (n= 6) at 2 dpe; 24 ± 11.8% at 4 dpe (n = 3); NeuroD1: 3.7 ± 0.5% at 2 dpe (n = 6); 1.6 ± 0.7% at 4 dpe (n = 3). (l) Distribution of the GFP-positive cells along the rostrocaudal axis. NeuroD1 expressing cells accumulated in proximal parts of the system. (M) Morphological analysis of cells in the SVZ/RMS. Three different classes were defined: (i) bipolar cells presenting tangential orientation, (ii) spherical cells, and (iii) branched cells presenting multiple processes in various directions (compare I). NeuroD1-expressing cells presented a highly branched morphology. Control: bipolar, 80.4%; spherical, 19.5%; branched, 0% (n = 133 cells). NeuroD1: bipolar, 5%; spherical, 16.8%; branched, 78% (n = 119 cells). Statistics: Mann-Whitney test. ns, not significant. **P < 0.01; ***P < 0.005. (Scale bar: 100 μm in E, F, G,and H; 25 μm in A, B, C, D,E, and F’; 10 μm in I; 5 μm in J.)

 

At 4 dpe, in the control situation, considerable amounts of strongly GFP+ RG cells were still present in the VZ (Fig. 2C asterisks), whereas NeuroD1 expression induced an almost complete loss of RG cells (Fig. 2 Dand K). At this time point, control cells were found along the entire SVZ and RMS. They showed generally tangential orientation and the typical morphology of migratory neuronal precursors. Large amounts of such cells were also found in the center of the OB (Fig. 2 G and L). NeuroD1 expression induced an accumulation of GFP-labeled cells in the SVZ (Fig. 2 D and L) at the expense of cells in the RMS (Fig. 2H,quantified in Fig. 2L). The accumulating cells did not have the appearance of migrating precursors but displayed complex multibranched morphologies (Fig. 2 F and F, examples in Fig. 2 I and I, quantified inFig. 2M). All principal processes of these cells were covered with small protrusions resembling filopodia (Fig. 2J). Such morphologically complex cells, strongly resembling neurons, were also predominant in and along proximal parts of the RMS (Fig. 2F). Interestingly, considerable amounts of multibranched cells were found outside of the periventricular region and the RMS, invading neighboring structures such as the striatum (Fig. 2F, arrows). There was a clear correlation between the quantity of transgene expression, as visualized by GFP fluorescence, and the above parameters. Thus, NeuroD1 induced dose-dependently a neuron-like morphology in cells in the SVZ, RMS, and surrounding tissues.

We characterized the NeuroD1 induced neuron-like cell population in the periventricular region using neuronal and glial markers (Fig. 3; examples in Fig. S5). Doublecortin (DCX), a microtubule-associated protein expressed in migratory neuronal precursors (26), was seen in 75.2 ± 4.5% of the cells in the control situation but showed a significant increase after expression of NeuroD1 (91.7 ± 2.2%). NeuN, a marker for most mature neuronal cell types in the brain (22) was low in controls (5.2 ± 1.4%, n = 8) but strongly induced by NeuroD1 (65.9 ± 4.5%, n = 9). Map2, a later generic neuronal marker (27), was also rare in control cells (14.1 ± 1.4%, n = 3) but highly expressed in the NeuroD1 condition (61.9 ± 2.7%, n = 3). GFAP and Olig2 did not show significant alterations due to NeuroD1 expression. Thus, the NeuroD1-induced ectopic cells with neuronal morphology in the SVZ and RMS showed molecular characteristics of neurons.

 

Fig. 3.

Fig. 3.

NeuroD1 induces generic neuronal markers in vivo Molecular phenotype of the cells located in the periventricular region (level 4 in Fig. 2l). Quantification representing the percentage of GFP-positive cells expressing the respective markers. DCX: control, 75.2 ± 4.5%, n = 5; NeuroD1, 91.7 ± 2.2%, n = 5. NeuN: control, 5.2 ± 1.4%, n = 8; NeuroD1, 65.9 ± 4.5%, n = 9. Map2: control, 14.1 ± 1.4%, n = 3; NeuroD1, 61.9 ± 2.7%, n = 3. Olig2: control, 6.8 ± 5%, n = 3; NeuroD1, 2.5 ± 0.5%, n = 3. GFAP: control, 0%, n = 3; NeuroD1, 0%, n = 2. Errors bars indicate SEM. Statistics: DCX and Map2, unpaired ttest; NeuN, Mann-Whitney test. ns, not significant. *P < 0.05; **P < 0.01; ***P < 0.005.

HighWire Press-hosted articles citing this article

  • ……..

    NeuroD1 Is Necessary For OB Interneuron Differentiation in Vivo.

    Next we asked whether NeuroD1 is essential for the generation of PGN. Given that NeuroD1 deficiency in mice is generally associated with perinatal lethality (14, 15, 21), we used a strategy based on RNAi in concert with postnatal in vivo electroporation to knock down NeuroD1 in the olfactory bulb neurogenic system. For validation, three different NeuroD1 specific shRNA vectors were cotransfected with a NeuroD1 expression construct into COS-7 cells. Western blot analysis demonstrated that two of the shRNAs, sh775 and sh776, efficiently inhibited production of the NeuroD1 protein, whereas sh777 induced a less efficient downregulation (sh775, 94.6%; sh776, 96.9%; sh777, 78.4%; corrected for loading against αtubulin; Fig. 4A). All three shRNAs were used for further in vivo studies.

    Fig. 4.

Fig. 4.

In vivo terminal neuronal differentiation of PGC is impaired in absence of NeuroD1. (A) Western blot analysis of protein extracts from cos-7 cells transfected with NeuroD1 or in combination with different NeuroD1 specific shRNAs. sh775 and sh776 strongly repressed NeuroD1 protein expression (94.6% and 96.9%, respectively), whereas sh777 repressed NeuroD1 by 74.8%. (B–H′′) Consequences of loss-of-function of NeuroD1 via in vivo postnatal electroporation at 4 and 15 dpe. (B–E) No differences were observed at the level of the lateral ventricle or in the RMS at 4 dpe. (F) Cell distribution along the rostro-caudal axis was normal (definition of levels in Fig. 2l). (G and H′′) Consequences of NeuroD1 knockdown on PGN morphology at 15 dpe. (G) Whereas shRNAs showing a strong effect on NeuroD1 expression strongly inhibited morphological differentiation, the weakly active shRNA 777 had only a minor effect compared with control. (H) Examples of cells that served for classification of PGN. Class1 cells present primary and secondary branching. Dendritic spines (arrowheads) indicate their synaptic integration in OB circuitry. Class 2 cells present a single primary branch. Class 3 cells present a spherical morphology and no branching. Errors bars indicate SEM. Statistics, unpaired t test. ns, not significant. **P < 0.01; ***P < 0.005. (Scale bar: 100 μm in B–E; 20 μm in H.

………

When the two highly active NeuroD1-specific shRNAs sh775 and sh776 were electroporated, the vast majority of cells in the GL showed simple morphologies with few or no processes (classes 2 and 3), whereas cells with complex neuronal morphologies were sparse (Fig. 4G). When the less-efficient shRNA sh777 was expressed, an intermediate degree of neuronal maturation was observed (Fig. 4G), suggesting a dose-dependent action of NeuroD1 under these conditions. Comparable results were obtained for the GCL. As in the PGL, knockdown of NeuroD1 induced a dose-dependent inhibition of terminal neuronal differentiation (Fig. S9 A and B).

Thus, knockdown of NeuroD1 did not notably interfere with early steps of interneuron generation, but induced a specific defect in the acquisition of the differentiated neuronal phenotype in the OB.

 

Discussion

Although considerable information is available concerning the generation, specification, and migration of neurons, little is known concerning the factors and regulatory cascades that maintain the immature neuronal precursor status or induce the exit from this state and trigger terminal differentiation. Using a systematic approach, we identified NeuroD1 as a candidate for the latter function and validated this role using gain- and loss-of function approaches.

In Xenopus, a late function of NeuroD1 has been suggested based on two lines of evidence (13). First, NeuroD1 is transitorily expressed in territories where neuronal differentiation occurs. Second, misexpression of NeuroD1 causes the premature differentiation of neuronal precursors into neurons. However, the observation that NeuroD1 could also convert presumptive epidermal cells into neurons pointed toward a determination function. Therefore, a doubtless discrimination between a proneural and a terminal differentiation function was not possible.

The above-cited pioneering work in the frog has been extended through the analysis of mice with mutations in the NeuroD1 gene (14, 15, 21). In the hippocampal dentate gyrus of such animals, granule cell precursors are generated correctly in the neuroepithelium and invade the hippocampal anlage. However, in the target structure, precursors show a severe deficit in proliferation, and a defined dentate gryus is not formed (15). In the mutant cerebellum, generation and migration of early precursors appear not to be affected. Nevertheless, once these cells become postmitotic, massive cell death is observed and the cerebellum is severely affected (14). Thus, in these systems a late function of NeuroD1 is already suggested. However, because of the complexity of the models and the relatively low level of resolution, the available information is still fragmentary.

We attempted to clarify the role of NeuroD1 in neuronal differentiation by analyzing its function during olfactory neurogenesis. Using SAGE, microarray, in situ hybridization, and lacZ knockin into the NeuroD1 locus, we have demonstrated that NeuroD1 is expressed in mature neurons of the OB but is absent from immature stages. These findings are in contrast to recent expression data based on a NeuroD1 antibody, suggesting expression of the transcription factor already in the SVZ and RMS (23, 29). However, our loss-of-function approach based on RNAi shows that NeuroD1 is dispensable for generation and migration of precursors but is necessary for their transition into neurons in the target layer. These findings are in agreement with those of a recent study based on conditional NeuroD1 mutants, which showed a comparable defect in the OB (29).

……

This work demonstrates that expression of a single transcription factor can induce massive ectopic neuronal differentiation of neural stem cells in the vertebrate forebrain. The existence of postnatal and adult neurogenesis holds potential for the treatment of neurodegenerative diseases (34). However, in many experimental paradigms, transplanted or recruited cells fail to undergo differentiation into neurons and either transdifferentiate into glia or remain immature precursors (18, 35). It appears conceivable to combine such approaches with the strong neuronal differentiation inducing activity of NeuroD1.

Scientists Unveil Critical Mechanism of Memory Formation

In a new study that could have implications for future drug discovery efforts for a number of neurodegenerative diseases, scientists from the Florida campus of The Scripps Research Institute (TSRI) have found that the interaction between a pair of brain proteins has a substantial and previously unrecognized effect on memory formation.
The study, which was published November 19, 2015 by the journal Cell, focuses on two receptors previously believed to be unrelated—one for the neurotransmitter dopamine, which is involved in learning and memory, reward-motivated behavior, motor control and other functions, and the other for the hormone ghrelin, which is known for regulating appetite as well as the distribution and use of energy.
“Our immediate question was, what is the ghrelin receptor doing in the brain since the natural ligand—ghrelin—for it is missing? What is it’s functional role?” said Roy Smith, chair of TSRI’s Department of Metabolism and Aging. “We found in animal models that when these two receptors interact, the ghrelin receptor changes the structure of the dopamine receptor and alters its signaling pathway.”
“This concept has potentially profound therapeutic implications,” said Andras Kern, the first author of the study and a staff scientist in the Smith lab, “pointing to a possible strategy for selective fine-tuning of dopamine signaling in neurons related to memory. By using small molecules binding to the ghrelin receptor we can enhance or inhibit dopamine signaling.”
Challenging the current theory, which involves canonical dopamine signaling in neurons, the new study shows that the biologically active ghrelin-dopamine receptor complex produces synaptic plasticity, the ability of the brain’s synapses (parts of nerve cells that communicate with other nerve cells) to grow and expand, the biological process underpinning long-term memory formation.
In addition, when the researchers blocked the ghrelin receptor, dopamine-dependent memory formation was inhibited in animal models, demonstrating the mechanism is essential to that process.
Combined with conclusions from earlier studies that showed a significant role for the ghrelin receptor in neurons that regulate food intake, insulin release and immune system deterioration due to aging, the new study further expands the ghrelin receptor’s importance. In animal models, ghrelin inhibits neuronal loss associated with Parkinson’s disease, and stroke, Smith noted, and the new study underlines its possible role in treating memory loss, age related or otherwise.
“All in all, it’s a pretty amazing receptor,” he said.
In addition to Smith and Kern, other authors of the study, “Hippocampal Dopamine/DRD1 Signaling Dependent on the Ghrelin Receptor,” are Maria Mavrikaki, Celine Ullrich, Rosie Albarran-Zeckler and Alicia Faruzzi Brantley of TSRI.
This work was supported by the National Institutes of Health (grant R01AG019230).
Hippocampal Dopamine/DRD1 Signaling Dependent on the Ghrelin Receptor
Andras Kern, Maria Mavrikaki3, Celine Ullrich4, Rosie Albarran-Zeckler, Alicia Faruzzi Brantley, Roy G. Smith
Figure thumbnail fx1
  • In hippocampal neurons GHSR1a and DRD1 forms heteromers in a complex with Gαq
  • DRD1-induced hippocampal synaptic plasticity is dependent on GHSR1a and Gαq
  • DRD1 mediated learning and memory is dependent on Gαq-PLC rather than Gαs signaling
  • DRD1-induced hippocampal memory is regulated by allosteric DRD1:GHSR1a interactions

The ghrelin receptor (GHSR1a) and dopamine receptor-1 (DRD1) are coexpressed in hippocampal neurons, yet ghrelin is undetectable in the hippocampus; therefore, we sought a function for apo-GHSR1a. Real-time single-molecule analysis on hippocampal neurons revealed dimerization between apo-GHSR1a and DRD1 that is enhanced by DRD1 agonism. In addition, proximity measurements support formation of preassembled apo-GHSR1a:DRD1:Gαqheteromeric complexes in hippocampal neurons. Activation by a DRD1 agonist produced non-canonical signal transduction via Gαq-PLC-IP3-Ca2+ at the expense of canonical DRD1 GαscAMP signaling to result in CaMKII activation, glutamate receptor exocytosis, synaptic reorganization, and expression of early markers of hippocampal synaptic plasticity. Remarkably, this pathway is blocked by genetic or pharmacological inactivation of GHSR1a. In mice, GHSR1a inactivation inhibits DRD1-mediated hippocampal behavior and memory. Our findings identify a previously unrecognized mechanism essential for DRD1 initiation of hippocampal synaptic plasticity that is dependent on GHSR1a, and independent of cAMP signaling.

 

 

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Studying Alzheimer’s biomarkers in Down syndrome

Larry H. Bernstein, MD, FCAP, Curator

LPBI

 

NIH supports new studies to find Alzheimer’s biomarkers in Down syndrome

Groundbreaking initiative will track dementia onset, progress in Down syndrome volunteers

http://www.nih.gov/news-events/news-releases/nih-supports-new-studies-find-alzheimers-biomarkers-down-syndrome

 

The National Institutes of Health has launched a new initiative to identify biomarkers and track the progression of Alzheimer’s in people with Down syndrome. Many people with Down syndrome have Alzheimer’s-related brain changes in their 30s that can lead to dementia in their 50s and 60s. Little is known about how the disease progresses in this vulnerable group. The NIH Biomarkers of Alzheimer’s Disease in Adults with Down Syndrome Initiative will support teams of researchers using brain imaging, as well as fluid and tissue biomarkers in research that may one day lead to effective interventions for all people with dementia.

The studies will be funded by the National Institute on Aging (NIA) and the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), both part of NIH. The institutes are jointly providing an estimated $37 million over five years to two highly collaborative projects, which enlist a number of leading researchers to the effort. To advance Alzheimer’s research worldwide, the teams will make their data and samples freely available to qualified researchers.

“This is the first large-scale Alzheimer’s biomarker endeavor to focus on this high-risk group,” said Laurie Ryan, Ph.D., chief of the Dementias of Aging Branch in NIA’s Division of Neuroscience, which leads NIH research on Alzheimer’s.  “Much like the long-established Alzheimer’s Disease Neuroimaging Initiative, the goal of this initiative is to develop biomarker measures that signal the onset and progression of Alzheimer’s in people with Down syndrome. Hopefully, one day, we will also use these biomarkers to determine the effectiveness of promising treatments.”

The link between Alzheimer’s and Down syndrome is well-known. People with Down syndrome are born with an extra copy of chromosome 21, which contains the amyloid precursor protein gene. This gene plays a role in the production of harmful amyloid plaque, sticky clumps that build up outside neurons in Alzheimer’s disease. Having three copies of this gene is a known risk factor for early-onset Alzheimer’s that can occur in people in their 30s, 40s and 50s. By middle age, most but not all adults with Down syndrome develop signs of Alzheimer’s, and a high percentage go on to develop symptoms of dementia as they age into their 70s.

The initiative establishes funding for two research teams that will pool data and standardize procedures, increase sample size, and collectively analyze data that will be made widely available to the research community. The teams will employ an array of biomarkers to identify and track Alzheimer’s-related changes in the brain and cognition for over 500 Down syndrome volunteers, aged 25 and older. The measures include:

  • Positron emission tomography (PET) scans that track levels of amyloid and glucose (energy used by brain cells); MRI of brain volume and function; and levels of amyloid and tau in cerebrospinal fluid and blood;
  • Blood tests to identify biomarkers in blood, including proteins, lipids and markers of inflammation;
  • Blood tests to collect DNA for genome-wide association studies that identify the genetic factors that may confer risk, or protect against, developing Alzheimer’s;
  • Evaluations of medical conditions and cognitive and memory tests to determine levels of function and monitor any changes;
  • For the first time in people with Down syndrome, PET brain scans that detect levels of tau, the twisted knots of protein within brain cells that are a hallmark Alzheimer’s disease.

Aside from earlier onset, Alzheimer’s in people with Down syndrome is similar to Alzheimer’s in others. The first symptom may be memory loss, although people with Down syndrome initially tend to show behavior changes and problems with walking.

“Over the past 30 years, the average lifespan of people with Down syndrome has doubled to 60 years—a  bittersweet achievement when faced with the possibility of developing Alzheimer’s,” said Melissa Parisi, M.D., Ph.D., chief of the NICHD Intellectual and Developmental Disabilities Branch, which leads NIH’s Down syndrome research. “There is much to learn about Alzheimer’s in Down syndrome, and we’re hopeful that these new projects will provide some answers. One mystery we hope to solve is whether or not the disease progresses at a faster rate in this group.”

Parisi noted that research into Alzheimer’s in Down syndrome is a key focus of the National Plan to Address Alzheimer’s Disease(link is external), which calls for improved care for specific populations that are unequally burdened by the disease, including people with Down syndrome, and for increased research that may lead to possible Alzheimer’s therapies.

Benjamin Handen, Ph.D., Department of Psychiatry, University of Pittsburgh, heads a team that involves investigators and data from: Banner Alzheimer’s Institute, Phoenix; Cambridge University, England; Alzheimer’s Disease Cooperative Study, San Diego; Laboratory of Neuro Imaging, University of Southern California, Los Angeles. Nicole Schupf, Ph.D., Columbia University Medical Center, New York City, leads a team involving investigators at: University of California, Irvine; Kennedy Krieger Institute/Johns Hopkins University, Baltimore; Massachusetts General Hospital/Harvard University, Boston; and the University of North Texas Health Sciences Center, Fort Worth.

Learn more about this topic at https://www.nia.nih.gov/alzheimers/publication/alzheimers-disease-people-down-syndrome.

About the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD): The NICHD sponsors research on development, before and after birth; maternal, child, and family health; reproductive biology and population issues; and medical rehabilitation. For more information, visit the Institute’s website at http://www.nichd.nih.gov.

About the National Institute on Aging: The NIA leads the federal government effort conducting and supporting research on aging and the health and well-being of older people. It provides information on age-related cognitive change and neurodegenerative disease specifically at its Alzheimer’s Disease Education and Referral (ADEAR) Center at www.nia.nih.gov/alzheimers.

About the National Institutes of Health (NIH): NIH, the nation’s medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.

 

 

NATIONAL PLAN TO ADDRESS ALZHEIMER’S DISEASE: 2015 UPDATE

pdf-document/national-plan-address-alzheimer%E2%80%99s-disease-2015-update (58 PDF pages)

Introduction

Vision Statement

National Alzheimer’s Project Act

Alzheimer’s Disease and Related Dementias

The Challenges

Framework and Guiding Principles

Goals as Building Blocks for Transformation

2015 Update

 

The Connection between Down Syndrome and Alzheimer’s Disease

Many, but not all, people with Down syndrome develop Alzheimer’s disease when they get older. Alzheimer’s is an irreversible, progressive brain disorder that slowly destroys memory and thinking skills and, eventually, the ability to carry out simple tasks.

Alzheimer’s disease is the most common cause of dementia among older adults. Dementia is the loss of cognitive functioning—thinking, remembering, and reasoning—and behavioral abilities to such an extent that it interferes with a person’s daily life and activities.

People with Down syndrome are born with an extra copy of chromosome 21, which carries the APP gene. This gene produces a specific protein called amyloid precursor protein (APP). Too much APP protein leads to a buildup of protein clumps called beta-amyloid plaques in the brain. By age 40, almost all people with Down syndrome have these plaques, along with other protein deposits, called tau tangles, which cause problems with how brain cells function and increase the risk of developing Alzheimer’s dementia.

However, not all people with these brain plaques will develop the symptoms of Alzheimer’s. Estimates suggest that 50 percent or more of people with Down syndrome will develop dementia due to Alzheimer’s disease as they age into their 70s.

Alzheimer’s Disease Symptoms

Many people with Down syndrome begin to show symptoms of Alzheimer’s disease in their 50s or 60s. But, like in all people with Alzheimer’s, changes in the brain that lead to these symptoms are thought to begin at least 10 years earlier. These brain changes include the buildup of plaques and tangles, the loss of connections between nerve cells, the death of nerve cells, and the shrinking of brain tissue (called atrophy).

The risk for Alzheimer’s disease increases with age, so it’s important to watch for certain changes in behavior, such as:

  • increased confusion
  • short-term memory problems (for example, asking the same questions over and over)
  • reduction in or loss of ability to do everyday activities

Other possible symptoms of Alzheimer’s dementia are:

  • seizures that begin in adulthood
  • problems with coordination and walking
  • reduced ability to pay attention
  • behavior and personality changes, such as wandering and being less social
  • decreased fine motor control
  • difficulty finding one’s way around familiar areas

Currently, Alzheimer’s disease has no cure, and no medications have been approved to treat Alzheimer’s in people with Down syndrome.

Down Syndrome and Alzheimer’s Disease Research

Alzheimer’s can last several years, and symptoms usually get worse over time.  Scientists are working hard to understand why some people with Down syndrome develop dementia while others do not. They want to know how Alzheimer’s disease begins and progresses, so they can develop drugs or other treatments that can stop, delay, or even prevent the disease process.

Research in this area includes:

  • Basic studies to improve our understanding of the genetic and biological causes of brain abnormalities that lead to Alzheimer’s
  • Observational research to measure cognitive changes in people over time
  • Studies of biomarkers (biological signs of disease), brain scans, and other tests that may help diagnose Alzheimer’s—even before symptoms appear—and show brain changes as people with Down syndrome age
  • Clinical trials to test treatments for dementia in adults with Down syndrome. Clinical trials are best the way to find out if a treatment is safe and effective in people.

 

Alzheimers Disease Neuroimaging Initiative (ADNI)

A public-private partnership, the purpose of ADNI is to develop a multisite, longitudinal, prospective, naturalistic study of normal cognitive aging, mild cognitive impairment (MCI), and early Alzheimer’s disease as a public domain research resource to facilitate the scientific evaluation of neuroimaging and other biomarkers for the onset and progression of MCI and Alzheimer’s disease.

Dr. Laurie Ryan of the NIA gives a brief overview of ADNI in this video:

https://youtu.be/0rBVe0Fwnik

Dr. Thomas Obisesan of Howard University, an ADNI study participant, and a study companion describe ADNI and what it’s like to be involved in the study

https://youtu.be/rK1yWvvHHl8

Learn more about this topic at https://www.nia.nih.gov/alzheimers/publication/alzheimers-disease-people-down-syndrome.

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Behavior

Curator: Larry H Bernstein, MD, FCAP

 

Behavior Brief

The Scientist

http://www.the-scientist.com//?articles.view/articleNo/43904/title/Behavior-Brief/

Wasp-directed webs make better cocoons?

Scientists have uncovered more detail about the unique relationship between the parasitic ichneumon wasp (Reclinervellus nielseni) and its arachnid host, the orb-weaving spider (Cyclosa argenteoalba). While the spider carries the wasp’s egg—and later, hatched larva—within its abdomen, the arachnid spins an atypical web, according to a study published last month (August 5) in The Journal of Experimental Biology. When the larva emerges, killing the spider host, the wasp uses the modified webbing to build a cocoon.

“This discovery—of enhanced behavior as opposed to merely switched behavior—is completely new, impressively demonstrated, and rather unexpected I think,” Mark Shaw an entomologist at the National Museum of Scotland, who was not involved in the study, told Newsweek.

According to The Vergescientists from Kobe University in Japan along with their collaborators determined that the modified web is similar to the orb-weaving spider’s resting web that it uses when it molts—only it is 40 times stronger. This may help the wasp larva build a more durable cocoon. Ecologist Sophie Labaude of the University of Burgundy in France, who was not involved in the work told The Verge that the altered web composition may be a coincidental side effect of chemicals thought to be introduced into the spider during the course of the parasitic infection.

Catharus ustulatus with a tracker on its back J. CRAVES

Some songbirds don’t set cruising altitude

A study published last month (August 12) in The Auk: Ornithological Advances reported the first complete flight-altitude data for a songbird, revealing that one species, the Swainson’s thrush (Catharus ustulatus), changes its altitude intermittently throughout its migration.

“I really thought that the birds would mostly behave like commercial aircraft, ascending to a particular altitude, leveling off and cruising near that altitude, and then coming down just before they landed,” study coauthor Melissa Bowlin of the University of Michigan-Dearborn said in a statement. “I was shocked when I made the first graph for the first bird, and thought it was an anomaly. The more data we obtained, however, the more often we saw the up-and-down pattern to the birds’ flight.”

Bowlin and her colleagues attached radio transmitters to nine Swainson’s thrushes captured from a forest in Illinois during the birds’ spring migration seasons between 2011 and 2013. Once the birds took off, the researchers followed them in a car, keeping track of the birds’ altitudes as they flew through different landscapes. The researchers found that the birds often altered their altitudes by more than 100 meters during their migration. While the authors noted that the precise locations at which the birds ascended and descended cannot be determined until more data are analyzed, they speculated that the birds’ decisions to change altitude may be related to atmospheric changes.

“Dr. Bowlin and her colleagues’ unique yet perplexing records of migrant altitudes raise a number of thought-provoking questions that have implications for species conservation,” Robert Diehl of the US Geological Survey’s Northern Rocky Mountain Science Center said in a statement.

FLICKR, LAGGEDONUSER

Bonobos reuse “peeps”

Humans may not be the only species that can disassociate their communication from their environment. Bonobos (Pan paniscus) also seem to produce the same high-pitched “peep” noises to express psychological states regardless of their context or circumstances, according to study published last month (August 4) in PeerJ. This ability, called functional flexibility, is analogous to the cries or laughter of a human infant, the study’s authors wrote.

“When I studied the bonobos in their native setting in the Congo, I was struck by how frequent their peeps were, and how many different contexts they produce them in,” study coauthor Zanna Clay, a psychologist at the University of Birmingham, told The Guardian. “It became apparent we couldn’t always differentiate between peeps. We needed to understand the context to get to the root of their communication.”

Clay and her colleagues recorded bonobo peeps made during a range of situations, including feeding, sleeping, and traveling. The researchers found that peeps produced during positive situations, such as feeding were indistinguishable from those made within neutral contexts such as resting. However, in negative circumstances such as a state of alarm, the bonobos’ peeps were acoustically different.

“We interpret this evidence as an example of an evolutionary early transition away from fixed vocal signaling towards functional flexibility,” Clay told The Guardian.

An ant (Pristomyrmex punctatus) stands guard over a Japanese oakblue caterpillar (Narathura japonica).WIKIMEDIA, L. SHYAMAL

Manipulation or mutalism?

A new study suggests that a species of Japanese ant (Pristomyrmex punctatus) that imbibes the sweet nectar secreted by Japanese oakblue butterfly (Narathura japonica) caterpillars must pay a price. According to a study published this summer (July 28) in Current Biology, chemicals in the nectar can effectively brainwash the ants, turning them into loyal bodyguards for the caterpillars.

An international group of researchers led by investigators at Kobe University found that ants who fed upon N. japonica’s sweet secretion displayed more aggressive behavior and had lower levels of dopamine in their brains than ants found near caterpillars that didn’t consume the nectar, according toScience.

The results suggest that the relationship between the ants and caterpillar may not be mutualistic, as previously thought, but may have an aspect of parasitism.

“It’s possible that these common food-for-defense interactions, which are typically assumed to be mutualistic, may in fact be maintained primarily through parasitic manipulation of ant behavior,” the authors wrote in their report.

NATURE COMMUNICATIONS, J. COSTELLO ET AL.

Young siphonophores take the lead

For physonect siphonophores (Nanomia bijuga), jellyfish-like marine creatures that travel together as a single unit, the youngest colony members alwaysride shotgun, according to a study published yesterday (September 1) in Nature Communications.

To cover distances of up to 200 meters a day to find food, N. bijuga colony members have to work together. “The younger swimming bells at the tip of the colony are responsible for turning. They generate a lot of torque,” study coauthor Kelly Sutherland, an oceanographer at the University of Oregon, said in a statement. “The older swimming bells toward the base of the colony are responsible for thrust.”

Sutherland and her colleagues recorded swimming colonies from Friday Harbor, Washington, and tracked how the organism displaced particles around it to discern the contribution each unit makes to the movement. They found that even small amounts of water displacement exerted by the youngest members at the tip of the colony had big impacts on which direction the unit travelled.

“They are like the handle of a door,” study coauthor John Costello, a biologist at the Marine Biological Laboratory in Woods Hole, Massachusetts, said in a statement. “If you push on a door near its hinges—its axis of rotation—the door is hard to open. But if you push on the door handle, which is far from the axis of rotation, the door opens easily. A little force placed with a big lever arm has a big effect on turning.”

The authors suggested that the siphonophore’s strategy involving multiple propulsion “engines” and efficient directional control could inspire improved designs for underwater vehicles.

Tags

songbirdplanktonparasitismparasitic wasporb web spidernon-human primatesmigration

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