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Is CRISPR a Solution to Familial Amyloid Polyneuropathy?

Posted in Genetics & Innovations in Treatment, Genetics & Pharmaceutical, Genome Biology, Neurodegenerative Diseases, Neurological Diseases, Neuroscience, tagged ATTR, cardiac amyloidosis, FAP, protein misfolding on April 13, 2016| Leave a Comment »

Is CRISPR a Solution to Familial Amyloid Polyneuropathy?

Author and Curator: Larry H. Bernstein, MD, FCAP

What FAP is

Familial amyloid polyneuropathy (FAP), also called transthyretin-related hereditary amyloidosis, transthyretin amyloidosis abbreviated also as ATTR ( hereditary form), or Corino de Andrade’s disease,^[1] is an autosomal dominant^[2] neurodegenerative disease. It is a form of amyloidosis, and was first identified and described by Portugueseneurologist Mário Corino da Costa Andrade, in 1952.^[3] FAP is distinct from senile systemic amyloidosis (SSA), which is not inherited, and which was determined to be the primary cause of death for 70% of supercentenarians who have been autopsied.^[4]

FAP is caused by a mutation of the TTR gene, located on human chromosome 18q12.1-11.2.^[5] A replacement of valine by methionine at position 30 (TTR V30M) is the mutation most commonly found in FAP.^[1] The variant TTR is mostly produced by the liver.^{[citation needed]} The transthyretin protein is a tetramer. The tetramer has to dissociate into misfolded monomers to aggregate into a variety of structures including amyloid fibrils. Because most patients are heterozygotes, they deposit both mutant and wild type TTR subnits.

FAP is inherited in an autosomal dominant manner.^[2] This means that the defective gene responsible for the disorder is located on anautosome (chromosome 18 is an autosome), and only one copy of the defective gene is sufficient to cause the disorder, when inherited from a parent who has the disorder.

FAP can be ameliorated by liver transplantation. Wikipedia https://en.wikipedia.org/wiki/Transthyretin-related_hereditary_amyloidosis

ATTRV30M Amyloidosis

ORPHA85447
Synonym(s)	ATTRV30M-related amyloidosis Familial amyloid polyneuropathy type I (Portuguese-Swedish-Japanese Type) TTR amyloid neuropathy Transthyretin amyloid neuropathy Transthyretin amyloid polyneuropathy
Prevalence	Unknown
Inheritance	Autosomal dominant
Age of onset	Adult

Familial amyloid polyneuropathy (FAP) or transthyretin (TTR) amyloid polyneuropathy is a progressive sensorimotor and autonomic neuropathy of adulthood onset. Weight loss and cardiac involvement are frequent; ocular or renal complications may also occur. The prevalence worldwide is unknown, but the prevalence in the general population in Japan has recently been estimated at around 1 per million.
FAP is clinically heterogeneous, with the clinical presentation depending on the genotype and geographic origin. FAP usually presents as a length-dependent sensory polyneuropathy with autonomic disturbances. Inaugural manifestations are paresthesiae, pain or trophic lesions of the feet, gastrointestinal disorders or weight loss. The most pronounced sensory loss involves pain and temperature sensation. Motor loss occurs later. Autonomic features include postural hypotension, and gastrointestinal and genitourinary disorders.
FAP is transmitted as an autosomal dominant trait and is caused by mutations in the TTR gene (18q12.1). 100 TTR mutations have been identified so far and are associated with varying patterns of organ involvement, age of onset and disease progression. The most common variant is the TTR Val30Met substitution for which several endemic foci have been identified most notably from Portugal, Japan and Sweden. However, the Val30Met phenotype varies between these countries.
Detection of amyloid-associated TTR mutations is required for diagnosis. However, identification of a disease-causing mutation is not considered as diagnostic because penetrance is variable. Clinical observation and tissue biopsy (from the nerve or kidney, labial salivary glands, subcutaneous fat tissue or rectal mucosa) are required for a definitive diagnosis: amyloid deposits are characterized by Congo red staining on light microscopy and green birefringence on polarized light microscopy.
The differential diagnosis should include diabetic neuropathy, chronic inflammatory demyelinating polyneuropathy (see this term), and light chain (AL), gelsolin and apolipoprotein A1 amyloidosis (see these terms). Antenatal diagnosis through chorionic villus sampling should be proposed to patients with early-onset (< 40 years) forms of FAP.
Genetic counseling should be offered to affected families and presymptomatic detection of relatives of an index case is important to allow early diagnosis.
Management of FAP should be multidisciplinary, involving a neurologist, geneticist, cardiologist and liver surgeon. Liver transplantation (LT) is currently the only treatment for preventing synthesis of the amyloidogenic variants of TTR. LT can stop progression of the disease during its early stages. Symptomatic treatments are essential for sensorimotor and autonomic neuropathy and visceral complications.
FAP is a severe and disabling disease. Severe cardiac, renal and ocular manifestations may develop. Death occurs within a mean interval of 10.8 years after onset of the inaugural symptoms and may occur suddenly or may be secondary to infections or cachexia.

Lancet Neurol. 2011 Dec;10(12):1086-97. doi: 10.1016/S1474-4422(11)70246-0.

Familial amyloid polyneuropathy

Planté-Bordeneuve V¹, Said G. Author information

Familial amyloid polyneuropathies (FAPs) are a group of life-threatening multisystem disorders transmitted as an autosomal dominant trait. Nerve lesions are induced by deposits of amyloid fibrils, most commonly due to mutated transthyretin (TTR). Less often the precursor of amyloidosis is mutant apolipoprotein A-1 or gelsolin. The first identified cause of FAP-the TTR Val30Met mutation-is still the most common of more than 100 amyloidogenic point mutations identified worldwide. The penetrance and age at onset of FAP among people carrying the same mutation vary between countries. The symptomatology and clinical course of FAP can be highly variable. TTR FAP typically causes a nerve length-dependent polyneuropathy that starts in the feet with loss of temperature and pain sensations, along with life-threatening autonomic dysfunction leading to cachexia and death within 10 years on average. TTR is synthesised mainly in the liver, and liver transplantation seems to have a favourable effect on the course of neuropathy, but not on cardiac or eye lesions. Oral administration of tafamidis meglumine, which prevents misfolding and deposition of mutated TTR, is under evaluation in patients with TTR FAP. In future, patients with FAP might benefit from gene therapy; however, genetic counselling is recommended for the prevention of all types of FAP.

The course and prognostic factors of familial amyloid polyneuropathy after liver transplantation

David Adams, Didier Samuel, Catherine Goulon-Goeau, …, Henri Bismuth, Gérard Said

DOI: http://dx.doi.org/10.1093/brain/123.7.1495 1495-1504

Familial amyloid polyneuropathy (FAP) associated with mutations of the transthyretin (TTR) gene is the most common type of FAP, a devastating disease causing death within 10 years after the first symptoms. Because most of the amyloidogenic mutated TTR is secreted by the liver, transplantation is widely used to treat these patients, but long-term quantitative evaluation of the effects of liver transplantation on the progression of the neuropathy are not available. We have treated 45 patients with symptomatic TTR-FAP, including 43 with the Met30 TTR gene mutation, and report on the results of periodic evaluation of markers of neuropathy in 25 of them, who have been followed for more than 2 years after liver transplantation (mean follow-up 4 years). The overall survival rates at 1 and 5 years were 82 and 60%, respectively. Urinary incontinence and a low Norris score at liver transplantation were associated with poorer outcome. The motor score stabilized in seven of 11 patients (64%) with mild sensorimotor neuropathy (walking unaided) and in two of the eight patients (25%) with severe sensorimotor deficit (walking with aid) at liver transplantation. In five other patients, deterioration of motor deficit occurred only within the first year after liver transplantation, but was progressive after this interval in two patients. None of the six patients with pure sensory neuropathy developed motor loss and superficial sensory loss remained unchanged. Two years after liver transplantation, the rate of myelinated axon loss in nerve biopsy specimens was markedly lower in seven transplanted patients (0.9/mm² of endoneurial area/month) than in non-transplanted patients (70/mm² of endoneurial area/month). Symptoms of dysautonomia and quantitated cardiocirculatory autonomic tests remained unchanged. In all patients, serum mutated TTR decreased to 2.5% of pre-liver transplantation values and remained at this level during follow-up. We presently recommend liver transplantation in FAP patients at onset of first symptoms and exclusion of those with a Norris score below 55 and/or with urinary incontinence.

Familial Amyloid Polyneuropathy (Amyloidotic transthyretin related neuropathy [ATTR]

Transthyretin (TTR) amyloidosis is an autosomal dominant disorder caused by the deposition of insoluble amyloid fibrils around peripheral nerves and in various tissues, including the heart muscle. Based on the predominant organ involvement, several distinct subtypes have been reported.

Familial amyloid polyneuropathy (FAP) aka TTR amyloid neuropathy is characterized by slowly progressive, peripheral sensorimotor polyneuropathy and autonomic dysfunction. Disease onset is usually in the third to fourth decade of life. Sensory neuropathy starts in the lower extremities with paresthesia, impaired pain and temperature sensation, followed by loss of motor function. Autonomic neuropathy usually manifests with orthostatic hypotension, constipation alternating with diarrhea, vomiting, impotence or hypohidrosis. Unrelated to neuropathy, other organs manifestations may include cardiomyopathy, vitreous opacities and CNS amyloidosis.

Leptomeningeal amyloidosis aka oculoleptomeningeal amyloidosis affects predominantly the central nervous system, sometimes combined with visual impairment.

Cardiac amyloidosis usually manifests in the sixth decade of life with progressive left ventricular hypertrophy and restrictive cardiomyopathy. In a subset of families with cardiac amyloidosis, peripheral neuropathy may be completely absent or very mild.

Treatment: Currently, the only effective treatment for FAP is an orthotopic liver transplant to stop production of misfolded amyloid protein. In patients with severe amyloid cardiomyopathy, a heart transplant may be necessary. Different drugs designed to prevent or alleviate accumulation of TTR amyloid protein (transthyretin amyloidois inhibitors) are currently under investigation.

Contemporary Reviews in Cardiovascular Medicine

Transthyretin (TTR) Cardiac Amyloidosis

Frederick L. Ruberg, John L. Berk

Circulation.2012; 126: 1286-1300 doi: 10.1161/CIRCULATIONAHA.111.078915

The systemic amyloidoses are a family of diseases induced by misfolded or misassembled proteins. Extracellular deposition of these proteins as soluble or insoluble cross β-sheets disrupts vital organ function.1 More than 27 different precursor proteins have the propensity to form amyloid fibrils.2 The particular precursor protein that misfolds to form amyloid fibrils defines the amyloid type and predicts the patient’s clinical course. Several types of amyloid can infiltrate the heart, resulting in progressive diastolic and systolic dysfunction, congestive heart failure, and death. Treatment of cardiac amyloidosis is dictated by the amyloid type and degree of involvement. Consequently, early recognition and accurate classification are essential.3

The diagnosis of amyloidosis requires histological identification of amyloid deposits. Congo Red staining renders amyloid deposits salmon pink by light microscopy, with a characteristic apple green birefringence under polarized light conditions (Figure 1). Additional immunohistochemical staining for precursor proteins identifies the type of amyloidosis (Figure 2).4 Ultimately, immunogold electron microscopy and mass spectrometry confer the greatest sensitivity and specificity for amyloid typing.5^,6

Transthyretin participates in beta-amyloid transport from the brain to the liver- involvement of the low-density lipoprotein receptor-related protein 1?

Mobina Alemi, Cristiana Gaiteiro, Carlos Alexandre Ribeiro, Luís Miguel Santos,João Rodrigues Gomes, Sandra Marisa Oliveira, ….., Maria João Saraiva & Isabel Cardoso

Scientific Reports 6, Article number: 20164 (2016) doi:10.1038/srep20164

Transthyretin (TTR) binds Aβ peptide, preventing its deposition and toxicity. TTR is decreased in Alzheimer’s disease (AD) patients. Additionally, AD transgenic mice with only one copy of the TTR gene show increased brain and plasma Aβ levels when compared to AD mice with both copies of the gene, suggesting TTR involvement in brain Aβ efflux and/or peripheral clearance. Here we showed that TTR promotes Aβ internalization and efflux in a human cerebral microvascular endothelial cell line, hCMEC/D3. TTR also stimulated brain-to-blood but not blood-to-brain Aβ permeability in hCMEC/D3, suggesting that TTR interacts directly with Aβ at the blood-brain-barrier. We also observed that TTR crosses the monolayer of cells only in the brain-to-blood direction, as confirmed by in vivo studies, suggesting that TTR can transport Aβ from, but not into the brain. Furthermore, TTR increased Aβ internalization by SAHep cells and by primary hepatocytes from TTR+/+ mice when compared to TTR−/− animals. We propose that TTR-mediated Aβ clearance is through LRP1, as lower receptor expression was found in brains and livers of TTR−/− mice and in cells incubated without TTR. Our results suggest that TTR acts as a carrier of Aβ at the blood-brain-barrier and liver, using LRP1.

Transthyretin (Prealbumin) in Health and Disease: Nutritional Implications

Annual Review of Nutrition

Vol. 14: 495-533 (Volume publication date July 1994)

DOI: 10.1146/annurev.nu.14.070194.002431

Y Ingenbleek, and V Young

Plasma Transthyretin as a Biomarker of Lean Body Mass and Catabolic States¹^,²

Yves Ingenbleek³^,* and Larry H Bernstein⁴

Adv Nutr Sep 2015; 6:572-580, 2015 doi: 10.3945/an.115.008508

Plasma transthyretin (TTR) is a plasma protein secreted by the liver that circulates bound to retinol-binding protein 4 (RBP4) and its retinol ligand. TTR is the sole plasma protein that reveals from birth to old age evolutionary patterns that are closely superimposable to those of lean body mass (LBM) and thus works as the best surrogate analyte of LBM. Any alteration in energy-to-protein balance impairs the accretion of LBM reserves and causes early depression of TTR production. In acute inflammatory states, cytokines induce urinary leakage of nitrogenous catabolites, deplete LBM stores, and cause an abrupt decrease in TTR and RBP4 concentrations. As a result, thyroxine and retinol ligands are released in free form, creating a second frontline that strengthens that primarily initiated by cytokines. Malnutrition and inflammation thus keep in check TTR and RBP4 secretion by using distinct and unrelated physiologic pathways, but they operate in concert to downregulate LBM stores. The biomarker complex integrates these opposite mechanisms at any time and thereby constitutes an ideally suited tool to determine residual LBM resources still available for metabolic responses, hence predicting outcomes of the most interwoven disease conditions.

Evaluating the binding selectivity of transthyretin amyloid fibril inhibitors in blood plasma
Hans E. Purkey, Michael I. Dorrell, and Jeffery W. Kelly*
Department of Chemistry and The Skaggs Institute of Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, MB12, La Jolla, CA 92037
http://www.pnas.org/content/98/10/5566.full.pdf

Transthyretin (TTR) tetramer dissociation and misfolding facilitate assembly into amyloid fibrils that putatively cause senile systemic amyloidosis and familial amyloid polyneuropathy. We have previously discovered more than 50 small molecules that bind to and stabilize tetrameric TTR, inhibiting amyloid fibril formation in vitro. A method is presented here to evaluate the binding selectivity of these inhibitors to TTR in human plasma, a complex biological fluid composed of more than 60 proteins and numerous small molecules. Our immunoprecipitation approach isolates TTR and bound small molecules from a biological fluid such as plasma, and quantifies the amount of small molecules bound to the protein by HPLC analysis. This approach demonstrates that only a small subset of the inhibitors that saturate the TTR binding sites in vitro do so in plasma. These selective inhibitors can now be tested in animal models of TTR amyloid disease to probe the validity of the amyloid hypothesis. This method could be easily extended to evaluate small molecule binding selectivity to any protein in a given biological fluid without the necessity of determining or guessing which other protein components may be competitors. This is a central issue to understanding the distribution, metabolism, activity, and toxicity of potential drugs.

Amyloid diseases are characterized by the conversion of soluble proteins or peptides into insoluble b-sheet-rich amyloid fibrils. There are currently 17 different human proteins known to form amyloid fibrils in vivo (1–4). These fibrils, or their oligomeric precursors, are thought to cause pathology either through disruption of normal cellular function or by direct toxicity (5–8). X-ray fibril diffraction and electron microscopy reconstruction of amyloid fibrils reveal filaments that have a lamellar cross b-sheet structure wrapped around one another (9–13). Folded proteins form amyloid fibrils through partial unfolding triggered by a change of local environment, a mutation in the protein, or both (8, 14–20).

Transthyretin (TTR) is a tetrameric protein composed of identical 127-aa subunits that fold into a b-sandwich tertiary structure. It is found in both the plasma (3.6 mM) and cerebrospinal fluid (CSF) (0.36 mM) of humans. The TTR tetramer has two negatively cooperative C2 symmetric thyroxine (T4)-binding sites (21–23). In the CSF, it binds and transports the thyroid hormone T4 and the retinol-binding protein (RBP), which in turn transports vitamin A. In the plasma, only 10–15% of TTR has T4 bound to it, as thyroid-binding globulin has an order of magnitude higher affinity for T4 than does TTR (24). TTR fibril formation is linked to two amyloid diseases in which the fibrils are composed of full-length protein. Deposition of wild-type TTR is associated with cardiac dysfunction in the disease senile systemic amyloidosis (SSA) (25, 26). More than 70 different single-site mutants have been linked to early-onset amyloid deposition in diseases with a spectrum of clinical manifestations, collectively referred to as familial amyloid polyneuropathy (FAP) (27–35).

We have discovered compounds, through both screening and structure-based design, that dramatically inhibit TTR amyloid fibril formation in vitro (36–42). To stabilize the TTR tetramer and thus prevent amyloid fibril formation in SSA and FAP, these small molecules must be able to selectively bind to TTR in human blood plasma over all other plasma proteins. Possible competitors include thyroid-binding globulin (TBG), which has an order of magnitude higher affinity for TTR’s natural ligand, T4; and albumin, which binds numerous hydrophobic small molecules and is present at a concentration two orders of magnitude higher than TTR, as well as the other plasma proteins. Historically, one was forced to choose two or three of the most likely protein competitors and evaluate their relative affinities for the small molecule in comparison to the protein of interest. The advantage of the approach outlined within this article is that the binding selectivity of TTR amyloid inhibitors in human plasma is determined without having to make assumptions as to which proteins may competitively bind the TTR ligand. Compounds that bind to TTR selectively in plasma are the best candidates for further evaluation in animal models and, ultimately, in human clinical trials.

Analysis of Nonsteroidal Antiinflammatory Drugs (NSAIDs)

The first compounds evaluated for selective binding to TTR in plasma were the NSAIDs previously identified to be potent TTR amyloid inhibitors in vitro (37, 42). Because these compounds are already approved by the Food and Drug Administration, they could easily be evaluated in human clinical trials for another indication if they proved to be selective TTR binders in human plasma. However, none of the NSAIDs exhibited significant selectivity for binding TTR in human plasma at a concentration of 10.8 mM (Table 1), although most exhibit a submicromolar Kd (37, 50). The most selective NSAIDs, flufenamic acid (1) and mefenamic acid (2), only had 0.2 eq of a maximum of 2 molar eq bound to TTR. However, fenoprofen (7), flurbiprofen (6), flufenamic acid (1), mefenamic acid (2), and diflunisal (4) all have maximal therapeutic plasma concentrations exceeding 20 mM (51, 52). When these compounds were incubated with plasma at their maximal therapeutic concentrations, flufenamic acid and diflunisal showed increased binding selectivity (stoichiometry) to TTR (Table 1). Diflunisal (4) is notable in that its 224 mM maximal therapeutic concentration leads to 0.85 eq of drug bound to TTR. Increasing the concentration of all other NSAIDs to their maximal therapeutic dose did not result in dramatic increases in binding selectivity, likely because of binding to other plasma proteins.

Analysis of the Remaining Lead Compounds. Approximately 40 additional small molecule amyloid inhibitors were evaluated for their ability to bind to TTR in plasma by using our immunoprecipitationyHPLC approach (Fig. 2). These compounds were derived from screening or structure-based design and identified as promising by an in vitro fibril formation assay (refs. 40–42; V. H. Oza, H. M. Petrassi, and J.W.K., unpublished data). Lead compounds having diverse structures including biaryls, biarylamines, stilbenes, and dibenzofurans showed promising selectivity (Table 2). Three compounds from this group (9-11) possess excellent TTR-binding selectivity in plasma. At a concentration of 10.8 mM, they exhibit saturation of .1 of the two possible binding sites in the TTR tetramer. Determination of the TTR-binding affinities of these three compounds in buffer shows that the Kd values do not correlate with the plasma binding selectivity (Table 2). For example, inhibitors 9 and 10 have greater than an order of magnitude difference in Kd but nearly identical binding selectivity (stoichiometry) to TTR in plasma. Moreover, compounds with modest binding selectivity, such as flufenamic acid (1), have been previously determined to have Kd values very similar to those exhibiting excellent selectivities (37). Mass spectrometry confirmed the identity of inhibitors 9-12 isolated by immunoprecipitation HPLC as the compounds that were initially incubated with plasma.

Binding to plasma proteins is an important factor in determining the overall distribution, metabolism, activity, and toxicity of a drug (55). In this particular case, we desire small molecules that bind to the plasma protein TTR over protein competitors whose identities are not known and likely change with the small molecule under evaluation. This binding is known to stabilize TTR’s normally folded state, thus preventing the conformational changes required for amyloidogenicity (14, 36). The immunoprecipitationyHPLCbased binding selectivity method outlined above allows quantification of the stoichiometry of small molecule binding to TTR in human plasma in the presence of all other plasma proteins and numerous competing small molecules without the use of tags, such as radiolabels, on the small molecule. Immunoprecipitation has been used previously to determine the stoichiometry of metal ion binding to specific plasma proteins (56, 57). However, to our knowledge, this is the first use of the technique to determine the binding selectivity of a small molecule to a single protein in human plasma. In principle, this approach is applicable to evaluate the binding selectivity of small molecules to any plasma protein, provided that a highly selective antibody for the protein can be generated, binding does not block the epitope or destroy it by conformational change, and appropriate wash steps can be introduced to avoid nonspecific binding of the small molecule and other proteins to the resin.

The Kelly Group Research

Transthyretin amyloid diseases: understanding the mechanism of proteotoxicity and inhibition of amyloid fibril formation

Figure 1: Three dimensional structure of the flufenamic acid-transthyretin tetramer complex. The small organic molecule, flufenamic acid, inhibits the conformational changes of transthyretin associated with amyloid fibril formation. Courtesy of Steven Johnson.

Transthyretin is a 55 kDa homotetrameric protein (Figure 1) that transports L-thyroxine and holo-retinol binding protein in the serum and cerebrospinal fluid of humans. We discovered that conformational changes alone enable transthyretin aggregation. Transthyretin amyloid formation in vivo is initiated by dissociation of the native tetramer under a denaturation stress of unknown origin. Subsequently, the resulting monomers can partially denature and misassemble into amyloid fibrils and other amorphous aggregates. Aggregation by transthyretin monomers under acidic conditions (conditions that render transthyretin amyloidogenesis fast on a laboratory time scale) occurs via a downhill polymerization mechanism, which means that every step along the amyloid formation pathway is energetically favorable and fast relative to tetramer dissociation. Thus, tetramer dissociation is rate limiting for transthyretin amyloid formation in the case of the wild type protein and for the vast majority of mutants.

Stabilizing the native tetrameric state of transthyretin should ameliorate transthyretin amyloid diseases. This hypothesis is supported by the observation of trans-suppression, in which compound heterozygotes expressing both a disease-associated mutation (e.g., V30M) and a trans-suppressor mutation (e.g., T119M) do not develop transthyretin amyloid disease. We have shown that the trans-suppressor mutation T119M inhibits amyloid formation by kinetically stabilizing (i.e., dramatically slowing the dissociation of) mixed transthyretin tetramers.

We have designed numerous small molecules based on the crystal structures of transthyretin that are now established to avidly bind to the unoccupied L-thyroxine binding sites within transthyretin. We have shown that small molecule binding to these sites inhibits amyloid formation in vitro by selectively stabilizing the native tetrameric state over the dissociative transition state, thus raising the energetic barrier for tetramer dissociation, dramatically slowing the rate-limiting step in the aggregation pathway. Over the past decade, we have identified and synthesized over 1000 small molecule inhibitors of transthyretin amyloid formation that group into half a dozen distinct families. The inhibitors are typically composed of two differentially-substituted aromatic rings connected by linkers of variable chemical composition.

These small molecule kinetic stabilizers either just bind to transthyretin or bind and then react chemoselectively with only one of eight lysine ε-amino groups within transthyretin. In collaboration with Dr. Ian Wilson (The Scripps Research Institute, Department of Molecular Biology), we systematically ranked a myriad of possibilities for the three substructures composing a typical transthyretin kinetic stabilizer. We used these data in a substructure combination strategy to develop very potent and selective transthyretin kinetic stabilizers. In collaboration with Dr. Joel Buxbaum (The Scripps Research Institute, Department of Molecular and Experimental Medicine), these and other compounds are being tested in cell and mouse models.

These data should allow us to be able to predict the structures of potent and selective transthyretin amyloidogenesis inhibitors that are largely devoid of characteristics undesirable for a clinical candidate.

In a recently completed placebo-controlled, double-blind clinical trial carried out by FoldRx Pharmaceuticals (a company that Kelly cofounded), benzoxazoles discovered by the Kelly Laboratory and developed by FoldRx Pharmaceuticals proved safe and effective at halting the progression of familial amyloid polyneuropathy by a myriad of metrics. This transthyretin kinetic stabilizer, now named Tafamidis, provides the first pharmacological evidence that the process of amyloid fibril formation causes the transthyretin amyloid diseases—reinvigorating efforts of other investigators and companies to do the same in other amyloid diseases. In collaboration with Dr. Martha Skinner and Dr. John Berk at Boston University, another kinetic stabilizer discovered by the Kelly Laboratory, diflunisal, is being tested in a second placebo-controlled human clinical trial for familial amyloid polyneuropathy that is currently enrolling patients.

In collaboration with Dr. Bill Balch (The Scripps Research Institute, Department of Cell Biology) and Dr. Luke Wiseman (The Scripps Research Institute, Department of Molecular and Experimental Medicine), we investigated the relationship between the secretion of destabilized transthyretin variants and the pathology of the disease they cause. The earliest onset (onset at 20-30 years of age) and most severe transthyretin amyloid diseases are generally associated with mutations that strongly destabilize the transthyretin tetramer, resulting in facile transthyretin dissociation and misfolded monomer misassembly into aggregates in the peripheral nerves. However, the most destabilized variants characterized to date, A25T and D18G transthyretin, do not cause an early onset systemic amyloid disease because they are intercepted by the degradation component of the proteostasis network within liver cells—the liver is where most of the transthyretin in the blood plasma is produced. Because of endoplasmic reticulum-associated degradation of these highly destabilized transthyretin variants within the secretory pathway of liver cells, the concentration of the destabilized mutant transthyretin in blood plasma would not be high enough to enable the amyloidogenesis responsible for pathology. Interestingly, these mutants lead to a very rare brain disease, with an intermediate age of onset (40-50 years old), because the choroid plexus is more permissive in its ability to secrete highly destabilized transthyretin variants for reasons that we are seeking to understand. These results suggest that endoplasmic reticulum-assisted folding mediated by the proteostasis network determines protein secretion in a tissue-specific manner, and we propose that its competition with endoplasmic reticulum-associated degradation may explain the appearance of tissue-selective amyloid diseases.

Is there a CRISPR alternative?

CRISPR biotech Intellia strikes licensing deal with Regeneron, readies IPO

By Ned Pagliarulo | April 11, 2016

http://www.biopharmadive.com/news/crispr-biotech-intellia-strikes-licensing-deal-with-regeneron-readies-ipo-1/417229/

Licensing deal with Regeneron to accelerate CRISPR biotech Intellia (Jennifer Doudna’s Start Up) for an IPO

Reporter: Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2016/04/12/licensing-deal-with-regeneron-to-accelerate-crispr-biotech-intellia-jennifer-doudnas-start-up-for-an-ipo/

Dive Brief:

Intellia Therapeutics, one of several companies working to develop CRISPR/Cas 9 technology commercially, on Monday filed to go public in an initially priced $120 million IPO. Concurrently, the biotech announced a collaboration and licensing deal with Regeneron Pharmaceuticals aimed at advancing up to 10 CRISPR-based programs, focusing primarily on liver diseases.
Regeneron will pay Intellia $75 million upfront, as well as investing $50 million in Intellia’s forthcoming IPO. Additionally, the agreement includes as much as $320 million in milestone payments, according to SEC filing documents.
The first program to be co-developed with Regeneron will target a rare genetic disorder known as ATTR, which can causes severely impaired nerve or cardiac function.

Intellia hopes CRISPR gene-editing can cure the genetic disorder ATTR, which is caused by a buildup of the transthyretin (TTR) protein in tissue. By “knocking out” TTR expression in the liver, Intellia could reduce or eliminate the disease-causing buildup.

A view by Larry H. Bernstein, MD, FCAP

I can only wish them success in a project that may well be a search for the Trojan Horse. TTR is also synthesized in the choroid plexus. In addition, knocking out TTR expression in the liver is not likely to fit a mechanism leading to TTR buildup in tissue. The TTR is a plasma tetrameric transport protein released into the circulation for transport of TH with a bound retinol-binding protein carrying one retinol per tetrameric protein. Other considerations are the nuclear release and the cell binding that have been extensively studied. The buildup in tissues is a misfolded protein – amyloid, which has extensively studied fibrils. Another issue is the actual functional transport of hormone and delivery of retinoid to cross the blood brain barrier.

Transthyretin participates in betaamyloid transport from the brain to the liver- involvement of the lowdensity lipoprotein receptor-related protein 1?

Mobina Alemi1,2,3, Cristiana Gaiteiro1,2, Carlos Alexandre Ribeiro1,2, Luís Miguel Santos1,2, João Rodrigues Gomes1,2, Sandra Marisa Oliveira1,2,3, Pierre-Olivier Couraud4, Babette Weksler5, Ignacio Romero6, Maria João Saraiva1,2 & Isabel Cardoso1
file:///C:/Users/Larry/Documents/Transthyretin%20participates%20in%20beta-amyloid%20transport%20from%20the%20brain%20to%20the%20liver%20srep20164.pdf

Distinctive binding and structural properties of piscine transthyretin

Claudia Follia, Nicola Pasquatob, Ileana Ramazzinaa, Roberto Battistuttab;c, Giuseppe Zanottib;c, Rodolfo Bernia;
FEBS Letters 555 (2003) 279-284

The thyroid hormone binding protein transthyretin (TTR) forms a macromolecular complex with the retinol-specific carrier retinol binding protein (RBP) in the blood of higher vertebrates. Piscine TTR is shown here to exhibit high binding affnity for L-thyroxine and negligible affnity for RBP. The 1.56 A % resolution X-ray structure of sea bream TTR, compared with that of human TTR, reveals a high degree of conservation of the thyroid hormone binding sites. In contrast, some amino acid differences in discrete regions of sea bream TTR appear to be responsible for the lack of protein-protein recognition, providing evidence for the crucial role played by a limited number of residues in the interaction between RBP and TTR. Overall, this study makes it possible to draw conclusions on evolutionary relationships for RBPs and TTRs of phylogenetically distant vertebrates.

Jeffery Kelly, Ph.D., Lita Annenberg Hazen Professor of Chemistry
Chairman, Department of Molecular and Experimental Medicine
California Campus, Scripps Institute
The Skaggs Institute for Chemical Biology
San Diego, CA

Studies directed at understanding the principles of b-sheet folding utilizing rapid kinetic and thermodynamic measurements are ongoing and focused on the WW domain, a 34-residue 3-stranded b-sheet. Chemical synthesis of the WW domain allows us to incorporate unique amino acids into the fold to probe structural determinants of transition state and ground state structure.

Awards & Professional Activities

Searle Scholar Award in Biomedical Sciences, 1991-1994
Camille and Henry Dreyfus Teacher Scholar Award, 1994
Texas A&M University Teacher Scholar Award, 1994-1995
The Biophysical Society National Lecturer, 1999
The Protein Society – Dupont Young Investigator Award, 1999
Alumni Distinguished Achievement Award, State University of New York at Fredonia, 2000
Arthur C. Cope Scholar Award, American Chemical Society, 2001

Selected References

Deechongkit, S.; Nguyen, H.; Dawson, P.E.; Gruebele, M.; Kelly, J.W. “Context Dependent Contributions of Backbone H-Bonding to b-Sheet Folding Energetics” Nature 2004, 430, 101-105.

Cohen,F.: Kelly, J.W. “Therapeutic Approaches to Protein Folding Diseases” Nature, 2003, 426, 905-910.

Hammarstrom, P.; Wiseman, R.L.; Powers, E.T.; Kelly, J.W., “Prevention of Transthyretin Amyloid Disease by Changing Protein Misfolding Energetics” Science 2003, 299, 713-716.

Sawkar, A.; Cheng, W-C.; Beutler, E.; Wong, C.-H.; Balch, W.E.; Kelly, J.W. “Chemical Chaperones Increase the Cellular Activity of N370S β glucosidase; A Therapeutic Strategy for Gaucher’s Disease” Proc.Natl.Acad.Sci., 2002, 99, 15428-15433.

Links

The Skaggs Institute for Chemical Biology

TSRI Scientists Discover Therapeutic Strategy for “Misfolding Diseases” Analogous to Alzheimer’s Disease

The Skaggs Institute Scientific Report

Colon Cancer

Posted in Bio Instrumentation in Experimental Life Sciences Research, Biological Networks, Gene Regulation and Evolution, Biomarkers & Medical Diagnostics, BioSimilars, CANCER BIOLOGY & Innovations in Cancer Therapy, Cancer Prevention: Research & Programs, Cell Biology, Signaling & Cell Circuits, Computational Biology/Systems and Bioinformatics, Disease Biology, Small Molecules in Development of Therapeutic Drugs, Drug Delivery Platform Technology, Genome Biology, Genomic Testing: Methodology for Diagnosis, Health Economics and Outcomes Research, Molecular Genetics & Pharmaceutical, Regulated Clinical Trials: Design, Methods, Components and IRB related issues, Technology Transfer: Biotech and Pharmaceutical, tagged APC, Clinical Trials, colon cancer, Colorectal cancer (CRC), EGFR mAb, FAP, KRAS, polyps on April 30, 2013| 4 Comments »

Colon Cancer

Author/Editor: Tilda Barliya PhD

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Word Cloud By Danielle Smolyar

Colorectal cancer is the third most common type of cancer diagnosed in the United States and is the third most common cause of cancer-related death. The majority of cases are sporadic, with hereditary colon cancer contributing up to 15% of all colon cancer diagnoses. Treatment consists of surgery for early-stage disease and the combination of surgery and adjuvant chemotherapy for advanced-stage disease. Management of metastatic disease has evolved from primary chemotherapeutic treatment to include resection of single liver and lung metastases in addition to resection of the primary disease and chemotherapy (1-4).

Courtesy WebMD site

In the United States, colorectal cancer (CRC) is the third most common type of cancer diagnosed and the third most common cause of cancer-related death in men and women. In 2010, an estimated 102,900 new cases of colon cancer were diagnosed (49,470 male, 53,430 female) and 51,370 patients (26,580 male, 24,790 female) died from CRC. The death rate from colon cancer decreased over the preceding decade, from 30.77 per 100,000 people to 20.5 per 100,000 people. The lifetime risk of developing colon cancer in industrialized nations is 5% and is stable or decreasing. In contrast, the incidence in developing countries continues to rise, hypothesized to be due to increased exposure to risk factors. It has been estimated that 1.5 million people in the United States will be living with CRC by 2020.The financial burden of caring for this population is significant: $4.5 to $9.6 billion per year.

Colon Cancer is divided into 5 types:

Sporadic: 60-85%
Familial: 10-30%
Hereditary non-Polyposis Colon Cancer (HNPCC): 5%
Familial Adenomatous Polyposis (FAP): 1%
Autosomal Dominant Inheritance

The molecular defects are of two types:

alterations that lead to novel or increased function of oncogenes
alterations that lead to loss of function of tumor-suppressor genes (TSGs)

Multiple genes are associated with the initiation and progression of the different syndromes of colon cancer and are summarized by Fearon ER in Table 1 (6):

**Table 1** Genetics of inherited colorectal tumor syndromes^a
Syndrome	Common features	Gene defect(s)
FAP	Multiple adenomatous polyps (>100) and carcinomas of the colon and rectum; duodenal polyps and carcinomas; fundic gland polyps in the stomach; congenital hypertrophy of retinal pigment epithelium	APC (>90%)
Gardner syndrome	Same as FAP; also, desmoid tumors and mandibular osteomas	APC
Turcot’s syndrome	Polyposis and colorectal cancer with brain tumors (medulloblastomas); colorectal cancer and brain tumors (glioblastoma)	APC
		MLH1, PMS2
Attenuated adenomatous polyposis coli	Fewer than 100 polyps, although marked variation in polyp number (from 5 to >1,000 polyps) observed in mutation carriers within a single family	APC(predominantly 5′ mutations)
Hereditary nonpolyposis colorectal cancer	Colorectal cancer without extensive polyposis; other cancers include endometrial, ovarian and stomach cancer, and occasionally urothelial, hepatobiliary, and brain tumors	MSH2
		MLH1
		PMS2
		GTBP, MSH6
Peutz-Jeghers syndrome	Hamartomatous polyps throughout the GI tract; mucocutaneous pigmentation; increased risk of GI and non-GI cancers	LKB1, STK11(30–70%)
Cowden disease	Multiple hamartomas involving breast, thyroid, skin, central nervous system, and GI tract; increased risk of breast, uterus, and thyroid cancers; risk of GI cancer unclear	PTEN (85%)
Juvenile polyposis syndrome	Multiple hamartomatous/juvenile polyps with predominance in colon and stomach; variable increase in colorectal and stomach cancer risk; facial changes	DPC4 (15%)
		BMPR1a(25%)
		PTEN (5%)
MYH-associated polyposis	Multiple adenomatous GI polyps, autosomal recessive basis; colon polyps often have somatic KRAS mutations	MYH

^aAbbreviations: FAP, familial adenomatous polyposis; GI, gastrointestinal.

Essentially all of the genes discussed above are conclusively implicated in subsets of CRC due to speciﬁc somatic defects that either activate or inactivate gene and protein function. It is hypothesized that essentially any gene with dysregulated expression in CRC—either increased or decreased expression—may have a functionally signiﬁcant role as an oncogene or a TSG, respectively. The aggregate data on the mutations and function of any given gene must be carefully evaluated to establish whether the gene truly contributes to CRC pathogenesis and whether it should be designated as an oncogene or a TSG (5,6).

The first proposed genetic model of CRC assumed that most CRCs arise from preexisting adenomatous lesions and that the accumulation of multiple gene defects is required for CRCs.

Benign GI tumors are a varied group, but localized lesions that project above the surrounding mucosa are commonly termed polyps. In humans, most colorectal polyps, particularly small polyps less than 5 mm in size, are hyperplastic (6). Most data indicate that hyperplastic polyps are not a major precursor to CRC; rather, the adenomatous polyp, or adenoma, is probably the important precursor lesion (7).

” Adenomas arise from glandular epithelium and are characterized by dysplastic morphology and altered differentiation of the epithelial cells in the lesion. The prevalence of adenomas in the United States is approximately 25% by age 50 and approximately 50% by age 70 (8)”. Only a fraction of adenomas progress to cancer, and progression probably occurs over years to decades. Individuals affected by syndromes that strongly predispose to adenomas, such as FAP, invariably develop CRCs by the third to ﬁfth decade of life if their colons are not removed”.

A more recent and modified version of the genetic model postulate that each gene defect described in the model occurs at high frequency only at particular stages of tumor development. This observation is the basis for assigning a relative order to the defects in a multistep pathway.

Colon Cancer and clinical Trails:

Mutations in the KRAS proto-oncogene are found in 40-45% of patients with CRC and occur mainly in exon 2 (codon 12 and 13) and to a lesser extent in exon 3 (codon 61) and exon 4 (codon 146). A number of studies have evaluated a potential prognostic role of KRAS in clinical practice for the treatment of colorectal cancer. However, clinical study design, reproducibility, interpretation and reporting of the clinical data remain important challenges.

Laurent-Puig’s group was the first to show the negative predictive value of KRAS mutations for response to the EGFR monoclonal antibody (mAb) cetuximab (11, 12, 13). Ever since then, a number of large phase II-III randomized studies have confirmed the negative predictive value of KRAS mutations for response to cetuximab and panitumumab treatment.

The role of KRAS mutations in predicting response to other therapies remains unclear. A subset analysis of patients treated in the phase III study of bevacizumab plus IFL (irinotecan, bolus 5-FU, and folinic acid) versus IFL showed that the clinical benefit of bevacizumab is independent of KRAS mutational status (11, 14).

“The KRAS biomarker story is unique in several ways. It represents the first biomarker integrated into clinical practice in CRC“.

The high prevalence of KRAS mutations in CRC and its strong negative predictive value for EGFR mAb therapies, has led to its rapid acceptance as a valuable biomarker. The EMEA, FDA and ASCO47 now recommend that all patients with metastatic CRC who are candidates for anti-EGFR mAb therapy should be tested for KRAS mutations and, if a KRAS mutation in codon 12 or 13 is detected, then patients should not receive anti-EGFR antibody therapy.

More so, Data from the PETACC-3 trial, presented at ASCO 2010, have shown that KRAS and BRAF mutant CRC tumors induce different gene-expression profiles, further reiterating that these tumors have a distinct underlying biology. Despite intensive progress in the field of genomic research, none of these genomic markers are used routinely in clinical trials. Only, nowadays, trials are starting to use specific gene-pathway” target in CRC clinical trials.

Samuel Constant et al. Colon Cancer: Current Treatments and Preclinical Models for the Discovery and Development of New Therapies

Summary:

Early studies are underway to understand the role of DNA methylation, chromatin modiﬁcation, changes in the patterns of mRNA and noncoding RNA expression, and changes in protein expression and posttranslational modiﬁcation. However, we do not yet have an indepth and comprehensive understanding of the pathogenesis of the biologically and clinically distinct subsets of CRC. Careful design of clinical trials end points and validation of the genes as potential prognostic markers will allow a better outcome for these patients.

Ref:

1. Sarah Popek, MD, and Vassiliki Liana Tsikitis, MD. Colorectal Cancer: A Review. OncLive November 10, 2011. http://www.onclive.com/publications/contemporary-oncology/2011/fall-2011/Colorectal-Cancer-A-Review

x. Martin Hefti., H.Maximilian Mehdorn., Ina Albert and Lutz Dörner. Fluorescence-Guided Surgery for Malignant Glioma: A Review on Aminolevulinic Acid Induced Protoporphyrin IX Photodynamic Diagnostic in Brain Tumors. Current Medical Imaging Reviews, 2010, 6, 1-5. http://www.hirslanden.ch/content/global/en/startseite/gesundheit_medizin/mediathek_bibliothek/fachartikel/verschiedenes/fluorescence_guidedsurgeryformalignantglioma/_jcr_content/download/file.res/FluorescenceGuidedSurgeryforMalignantGlioma.pdf

2. Oguz Akin, Sandra B. Brennan., D. David Dershaw., Michelle S. Ginsberg., Marc J. Gollub., Heiko Sch€oder., David M. Panicek, and Hedvig Hricak. Advances in Oncologic Imaging: Update on 5 Common Cancers. CA CANCER J CLIN 2012;62:364–393. http://onlinelibrary.wiley.com/doi/10.3322/caac.21156/pdf

3. O’Donnell, Kevin et al. Nanoparticulate systems for oral drug delivery to the colon. International Journal of Nanotechnology, 2010, 8, 1/2, 4-20. “Colonic Navigation: Nanotechnology Helps Deliver Drugs to Intestinal Target”. http://www.sciencedaily.com/releases/2010/11/101104154553.htm

4. Perumal V. Molecular Therapy and Nanocarrier Based Drug Delivery to Colon Cancer: Targeted Molecular Therapy (AEE788 and Celecoxib) and Drug Delivery (Celecoxib) To Colon Cancer. http://www.amazon.com/Molecular-Therapy-Nanocarrier-Delivery-Cancer/dp/3659162558

5. Xiaoyun Liao, Paul Lochhead, Reiko Nishihara, Teppei Morikawa, Aya Kuchiba, Mai Yamauchi, Yu Imamura, Zhi Rong Qian, Yoshifumi Baba, Kaori Shima, Ruifang Sun, Katsuhiko Nosho, Jeffrey A. Meyerhardt, Edward Giovannucci, Charles S. Fuchs, Andrew T. Chan, Shuji Ogino. Aspirin Use, TumorPIK3CAMutation, and Colorectal-Cancer Survival. New England Journal of Medicine, 2012; 367 (17): 1596 DOI:10.1056/NEJMoa1207756. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3532946/

Gene Mutation Identifies Colorectal Cancer Patients Who Live Longer With Aspirin Therapy. http://www.sciencedaily.com/releases/2012/10/121024175357.htm

6. Fearon ER. Molecular Genetics of Colorectal Cancer. Annual Review of Pathology: Mechanisms of Disease 2011; 6: 479-507.http://www.annualreviews.org/doi/pdf/10.1146/annurev-pathol-011110-130235

7. Jass JR. 2007. Classiﬁcation of colorectal cancer based on correlation of clinical, morphological and molecular features. Hisopathology 50:113–130. http://www.amedeoprize.com/ap/pdf/histopathology.pdf

8. Rex DK, Lehman GA, Ulbright TM, Smith JJ, Pound DC, et al. Colonic neoplasia in asymptomatic persons with negative fecal occult blood tests: inﬂuence of age, gender, and family history. Am. J. Gastroenterol 1993. 88:825–831.http://www.ncbi.nlm.nih.gov/pubmed/8503374

9. Kerber RA, Neklason DW, Samowitz WS, Burt RW. Frequency of familial colon cancer and hereditary nonpolyposis colorectal cancer (Lynch syndrome) in a large population database. Fam. Cancer 2005; 4:239–44. http://www.ncbi.nlm.nih.gov/pubmed/16136384

10. Kinzler KW, Vogelstein B. Lessons from hereditary colorectal cancer. Cell 1996: 87:159–170. http://users.ugent.be/~fspelema/les%204-5%20HMG/kinzler%20clon.pdf

11. Sandra Van Schaeybroeck, Wendy L. Allen, Richard C. Turkington & Patrick G. Johnston. Implementing prognostic and predictive biomarkers in CRC clinical trials.(colorectal cancer)(Clinical report). Nature Reviews Clinical Oncology 2011: 8; 222-232. http://www.nature.com/nrclinonc/journal/v8/n4/abs/nrclinonc.2011.15.html

12. Lievre, A. et al. KRAS mutation status is predictive of response to cetuximab therapy in colorectal cancer. Cancer Res. 66 2006: 3992-3995. http://hwmaint.cancerres.aacrjournals.org/cgi/content/full/66/8/3992

13. Lievre, A. et al. KRAS mutations as an independent prognostic factor in patients with advanced colorectal cancer treated with cetuximab. J. Clin. Oncol. 2008: 26, 374-379. http://jco.ascopubs.org/content/26/3/374.full.pdf

14. Hurwitz, H. I., Yi, J., Ince, W., Novotny, W. F. & Rosen, O. The clinical benefit of bevacizumab in metastatic colorectal cancer is independent of K-ras mutation status: analysis of a phase III study of bevacizumab with chemotherapy in previously untreated metastatic colorectal cancer. Oncologist 2009: 14, 22-28. http://theoncologist.alphamedpress.org/content/14/1/22.full

Amyloidosis with Cardiomyopathy

Posted in Biomarkers & Medical Diagnostics, Cardiovascular Pharmacogenomics, Cerebrovascular and Neurodegenerative Diseases, Chemical Biology and its relations to Metabolic Disease, Chemical Genetics, Disease Biology, Small Molecules in Development of Therapeutic Drugs, Frontiers in Cardiology and Cardiovascular Disorders, Genome Biology, Genomic Testing: Methodology for Diagnosis, Human Immune System in Health and in Disease, International Global Work in Pharmaceutical, Liver & Digestive Diseases Research, Medical and Population Genetics, Medical Imaging Technology, Image Processing/Computing, MRI, CT, Nuclear Medicine, Ultra Sound, Molecular Genetics & Pharmaceutical, Personalized and Precision Medicine & Genomic Research, Pharmaceutical Industry Competitive Intelligence, Pharmacotherapy and Cell Activity, Pharmacotherapy of Cardiovascular Disease, Proteomics, Systemic Inflammatory Response Related Disorders, tagged AL amyloidosis, Amyloidosis, Conditions and Diseases, Familial Amyloid, FAP, health, Transthyretin, Transthyretin-related hereditary amyloidosis, TTR, United States on March 31, 2013| 11 Comments »

Amyloidosis with Cardiomyopathy

Author: Larry H Bernstein, MD, FACP

Introduction

Amyloidosis describes the various clinical syndromes that occur as a result of damage by amyloid deposits in tissues and organs throughout the body. Systemic amyloidosis is a relatively rare multisystem disease caused by the deposition of misfolded protein in various tissues and organs. The term amyloid describes the deposition in the extracellular space of certain proteins in a highly characteristic, insoluble fibrillar form. The disease entity is a disorder of misfolded or misassembled proteins. There is extracellular amyloid fiber laid down as cross β-sheets disrupting organ function, which may affect the pancreas, kidney, autonomic nervous system, the heart, and in one form causes carpal tunnel syndrome.

It may present to almost any specialty, and diagnosis is frequently delayed. Cardiac involvement is a leading cause of morbidity and mortality, especially in primary light chain (AL) amyloidosis and in both wild-type and hereditary transthyretin amyloidosis. The heart is also occasionally involved in acquired serum amyloid A type (AA) amyloidosis and other rare hereditary types. Clinical phenotype varies greatly between different types of amyloidosis, and even the cardiac presentation has a great spectrum. The incidence of amyloidosis is uncertain, but it is thought that the most frequently diagnosed AL amyloidosis has an annual incidence of 6 to 10 cases per million population in the United Kingdom and United States.

The molecular basis for this particular phenomenon came with the extensive work done on multiple myeloma, antibody structure, and light chains. In 1950, the discovery of a familial amyloid polyneuropathy was described in Portugal, and there were similar diseases in Sweden and Japan. There were 72 known variants of transthyretin (TTR) in 1995, and now there are 100. In addition, the occurance of different TTR associated variants with and without (amyloid) is found is Brazil, UK, US, Israel, Spain, France, Germany, Denmark, and Africa. The table of variants, organ damage, and geographic location is too large to place on this document. If we refer to amyloid cardiomyopathy, it is exclusively a primary amyloidopathy, not secondary to light chain disorders or an inflammatory disease. If we consider amyloidosis, we also have to consider family history, organ dysfunction, and we have to make a distinction between primary cardiac involvement, autonomic nervous system instability, and the two coexisting. Familial amyloid polyneuropathy (FAP) is an extremely debilitating and progressive disease that is only treatable by liver transplantation. Primary amyloid cardiomyopathy has been treated by heart transplant. The qualifying statement here is, it depends.

Primary and Secondary Amyloidoses

Amyloid was originally described by pathologists based on microscopy. Amyloidoses are a systemic primary or secondary disease. There are distinctions to be made based on location and type. The clinical significance of amyloid disease varies enormously, ranging from incidental asymptomatic deposits to localized disease through to rapidly fatal systemic forms that can affect multiple vital organs.

Common causes of secondary amyloidosis are – light chain production (AL) as in plasma cell dyscrasia, amyloid A (AA), senile systemic amyloidosis (diagnosed rarely in life). The systemic amyloidoses are designated by a capital A (for amyloid) followed by the abbreviation for the chemical identity of the fibril protein. Thus, TTR amyloidosis is abbreviated ATTR, and immunoglobulin light chain type amyloidosis is abbreviated AL. Both normal-sequence TTR and variant-sequence TTR form amyloidosis. Normal-sequence TTR forms cardiac amyloidosis in elderly people, termed senile cardiac amyloidosis (SCA). When it was recognized that SCA is often accompanied by microscopic deposits in many other organs, the alternative name senile systemic amyloidosis (SSA) was proposed. Both terms are now used.

Currently available therapy is focused on reducing the supply of the respective amyloid fibril precursor protein and supportive medical care, which together have greatly improved survival. Chemotherapy and anti-inflammatory treatment for the disorders that underlie AL and AA amyloidosis are guided by serial measurements of the respective circulating amyloid precursor proteins, i.e. serial serum free light chains in AL and serum amyloid A protein in AA type.

Quality of life and prognosis of some forms of hereditary systemic amyloidosis can be improved by liver and other organ transplants. Various new therapies, ranging from silencing RNA, protein stabilizers to monoclonal antibodies, aimed at inhibiting fibril precursor supply, fibril formation or the persistence of amyloid deposits, are in development; some are already in clinical phase.

Ann Clin Biochem May 2012; 49(3 ): 229-241 http://acb.2011.011225v1 49/3/229

What is transthyretin (TTR)?

TTR is a tetramer of 4 127 amino acid subunits synthesized by the liver that circulates as a transporter of thyroxin, and with retinol-binding protein, transports vitamin A. It was originally defined by the migration in electrophoresis more anodal to albumin, hence, prealbumin. It is present in cerebrospinal fluid, secreted by the choroid plexus. The TTR monomer contains 8 antiparallel beta pleated sheet domains. TTR can be found in plasma and in cerebrospinal fluid and is synthesized by the choroid plexus of the brain and, to a lesser degree, by the retina. Its gene is located on the long arm of chromosome 18 and contains 4 exons and 3 introns.

The concentration in serum can be expected to be above 20 mg/dL in a health adult, but the protein decreases by 1 mg/dL/day postoperatively, and it decreases with acute or chronic renal failure, pneumonia or sepsis, rising again with the onset of anabolism. Patients in the pulmonary intensive care unit have TTR levels that remain low for 7-10 days, but followup data for the remainder of the hospital stay or in relationship to readmission in the six months after release from hospital care was not part of the study.

A decrease in TTR is associated with the systemic inflammatory response, whereby, the liver reprioritizes the synthesis of proteins with an increase in acute phase reactants (APRs), namely, C-reactive protein (CRP) and a-1 acid glycoprotein, and decreased albumin and TTR. The inflammatory condition maintains a euthyroid status with decreased TTR because of the availability of free thyroxine in equilibrium with the lower binding protein. This has been referred to sick euthyroid status. The role in thyroxine transport is not insignificant, as chronic protein malnutrition is associated with hypothyroidism, as originally described by Prof. Yves Ingenbleek, Univ. Louis Pateur, Starsbourg, Fr. in Senegalese children with Kwashiorkor. However, the importance of TTR as a unique biomarker is not to be downgraded because of what is often refered to as “an inverted APR”.

Transthyretin was discovered to be a good reflection of the “lean body mass”, by Vernon Young, MIT, and Ingenbleek, as a result of 3 decades of study. The ratio of S:N being 1:20 in plant proteins and 1:12.5 in animal sources, is closely related to methylation reactions and sustained deficiency of S intake results in elevated homocysteine level.

What is FAP?

Familial amyloid polyneuropathy (FAP), also called transthyretin-related hereditary amyloidosis, transthyretin amyloidosis or Corino de Andrade’s disease, is an autosomal dominant neurodegenerative disease. It is a form of amyloidosis, and was first identified and described by Portuguese neurologist Mário Corino da Costa Andrade, in the 1950s.FAP is distinct from senile systemic amyloidosis (SAS), which is not inherited, and which was determined to be the primary cause of death for 70% of supercentenarians who have been autopsied.

Familial amyloid polyneuropathy (FAP) is an extremely debilitating and progressive disease that is only treatable by liver transplantation. Primary amyloid cardiomyopathy has been treated by heart transplant. The qualifying statement here is, it depends. Those patients with TTR-amyloidopathy have a specific gene substitution in the TTR gene. Consequently, there is circulation TTR, but it is not effectively involved in thyroxine transport.

Characteristics.

Usually manifesting itself between 20 and 40 years of age, it is characterized by pain, paresthesia, muscular weakness and autonomic dysfunction. In its terminal state, the kidneys and the heart are affected. FAP is characterized by the systemic deposition of amyloidogenic variants of the transthyretin protein, especially in the peripheral nervous system, causing a progressive sensory and motor polyneuropathy. The age at symptom onset, pattern of organ involvement, and disease course vary, but most mutations are associated with cardiac and/or nerve involvement. The gastrointestinal tract, vitreous, lungs, and carpal ligament are also frequently affected. When the peripheral nerves are prominently affected, the disease is termed familial amyloidotic polyneuropathy (FAP). When the heart is involved heavily but the nerves are not, the disease is called familial amyloid cardiomyopathy (FAC). Regardless of which organ is primarily targeted, the general term is simply amyloidosis-transthyretin type, abbreviated ATTR.

Genetics.

TTR mutations accelerate the process of TTR amyloid formation and are the most important risk factor for the development of clinically significant ATTR. More than 85 amyloidogenic TTR variants cause systemic familial amyloidosis. The variant TTR is mostly produced by the liver. Amyloidogenic TTR mutations destabilize TTR monomers or tetramers, allowing the molecule to more easily attain an amyloidogenic intermediate conformation. The tetramer has to dissociate into misfolded monomers to aggregate into a variety of structures including amyloid fibrils. Because most patients are heterozygotes, they deposit both mutant and wild type TTR subnits.
Familial amyloid polyneuropathy has an autosomal dominant pattern of inheritance. FAP is caused by a mutation of the TTR gene, located on human chromosome 18q12.1-11.2. A replacement of valine by methionine at position 30 (TTR V30M) is the mutation most commonly found in FAP.
The disease in the TTR V30M kindreds was termed FAP because early symptoms arose from peripheral neuropathy, but these patients actually have systemic amyloidosis, with widespread deposits often involving the heart, gastrointestinal tract, eye, and other organs.
TTR V122I: This variant, carried by 3.9% of African Americans and over 5% of the population in some areas of West Africa, increases the risk of late-onset (after age 60 years) cardiac amyloidosis. It appears to be the most common amyloid-associated TTR variant worldwide. Affected patients usually do not have peripheral neuropathy.
TTR T60A: This variant causes late-onset systemic amyloidosis with cardiac, and sometimes neuropathic, involvement. This variant originated in northwest Ireland and is found in Irish and Irish American patients.
TTR L58H: Typically affecting the carpal ligament and nerves of the upper extremities, this variant originated in Germany. It has spread throughout the United States but is most common in the mid-Atlantic region.
TTR G6S: This is the most common TTR variant, but it appears to be a neutral polymorphism not associated with amyloidosis. It is carried by about 10% of people of white European descent.

Cardiac transthyretin (TTR) amyloidosis

Cardiac amyloidosis of transthyretin fibril protein (ATTR) type is an infiltrative cardiomyopathy characterised by ventricular wall thickening and diastolic heart failure. More than 27 different precursor proteins have the propensity to form amyloid fibrils. The particular precursor protein that misfolds to form amyloid fibrils defines the amyloid type and predicts the patient’s clinical course. Several types of amyloid can infiltrate the heart, resulting in progressive diastolic and systolic dysfunction, congestive heart failure, and death. Increased access to cardiovascular magnetic resonance imaging has led to a marked increase in referrals to St George’s University of London, London (Dr. Jason Dungu) of Caucasian patients with wild-type ATTR (senile systemic) amyloidosis and Afro-Caribbean patients with the hereditary ATTR V122I type. Both subtypes present predominantly as isolated cardiomyopathy. The differential diagnosis includes cardiac amyloid light-chain (AL) amyloidosis, which has a poorer prognosis and can be amenable to chemotherapy.

Clinical Presentation

Cardiac amyloidosis, irrespective of type, presents as a restrictive cardiomyopathy characterized by progressive diastolic and subsequently systolic biventricular dysfunction and arrhythmia.1 Key “red flags” to possible systemic amyloidosis include nephrotic syndrome, autonomic neuropathy (eg, postural hypotension, diarrhea), soft-tissue infiltrations (eg, macroglossia, carpal tunnel syndrome, respiratory disease), bleeding (eg, cutaneous, such as periorbital, gastrointestinal), malnutrition/cachexia and genetic predisposition (eg, family history, ethnicity). Initial presentations may be cardiac, with progressive exercise intolerance and heart failure. Other organ involvement, particularly in AL amyloidosis, may cloud the cardiac presentation (eg, nephrotic syndrome, autonomic neuropathy, pulmonary or bronchial involvement). Pulmonary edema is not common early in the disease process, but pleural and pericardial effusions and atrial arrhythmias are often seen. Syncope is common and a poor prognostic sign. It is typically exertional or postprandial as part of restrictive cardiomyopathy, sensitivity to intravascular fluid depletion from loop diuretics combined with autonomic neuropathy, or conduction tissue involvement (atrioventricular or sinoatrial nodes) or ventricular arrhythmia. The latter may rarely cause recurrent syncope. Disproportionate septal amyloid accumulation mimicking hypertrophic cardiomyopathy with dynamic left ventricular (LV) outflow tract obstruction is rare but well documented. Myocardial ischemia can result from amyloid deposits within the microvasculature. Atrial thrombus is common, particularly in AL amyloidosis

Diagnosis and Treatment

imaging – Cardiovascular Magnetic Resonance in Cardiac Amyloidosis*.

Cardiac amyloidosis can be diagnostically challenging. Cardiovascular magnetic resonance (CMR) can assess abnormal myocardial interstitium. In cardiac amyloidosis, CMR shows a characteristic pattern of global subendocardial late enhancement coupled with abnormal myocardial and blood-pool gadolinium kinetics. The findings agree with the transmural histological distribution of amyloid protein and the cardiac amyloid load.

*AM Maceira; J Joshi; SK Prasad; J Charles Moon, et al. Royal Brompton Hospital, London;

The diagnosis of amyloidosis requires histological identification of amyloid deposits. Congo Red staining renders amyloid deposits salmon pink by light microscopy, with a characteristic apple green birefringence under polarized light conditions. Additional immunohistochemical staining for precursor proteins identifies the type of amyloidosis. Ultimately, immunogold electron microscopy and mass spectrometry confer the greatest sensitivity and specificity for amyloid typing.

Treatment of cardiac amyloidosis is dictated by the amyloid type and degree of involvement. Consequently, early recognition and accurate classification are essential.

Novel diagnostic and surveillance approaches using imaging (echocardiography, cardiovascular magnetic resonance), biomarkers (brain natriuretic peptide [BNP], high-sensitivity troponin), new histological typing techniques, and current and future treatments, including approaches directly targeting the amyloid deposits.

Etiology

Amyloidosis is caused by the extracellular deposition of autologous protein in an abnormal insoluble β-pleated sheet fibrillary conformation—that is, as amyloid fibrils. More than 30 proteins are known to be able to form amyloid fibrils in vivo, which cause disease by progressively damaging the structure and function of affected tissues. Amyloid deposits also contain minor nonfibrillary constituents, including serum amyloid P component (SAP), apolipoprotein E, connective tissue components (glycosaminoglycans, collagen), and basement membrane components (fibronectin, laminin). Amyloid deposits can be massive, and cardiac or other tissues may become substantially replaced. Amyloid fibrils bind Congo red stain, yielding the pathognomonic apple-green birefringence under cross-polarized light microscopy that remains the gold standard for identifying amyloid deposits.

Heart 2012;98:1546-1554 http://dx.doi.org/10.1136/heartjnl-2012-301924

AL Amyloidosis

AL amyloidosis is caused by deposition of fibrils composed of monoclonal immunoglobulin light chains and is associated with clonal plasma cell or other B-cell dyscrasias. The spectrum and pattern of organ involvement is very wide, but cardiac involvement occurs in half of cases and is sometimes the only presenting feature. Cardiac AL amyloidosis may be rapidly progressive. Low QRS voltages, particularly in the limb leads, are common. Thickening of the LV wall is typically mild to moderate and is rarely >18 mm even in advanced disease. Cardiac AL amyloid deposition is accompanied by marked elevation of the biomarkers BNP and cardiac troponin, even at an early stage. Involvement of the heart is the commonest cause of death in AL amyloidosis and is a major determinant of prognosis; without cardiac involvement, patients with AL amyloidosis have a median survival of around 4 years, but the prognosis among affected patients with markedly elevated BNP and cardiac troponin (Mayo stage III disease) is on the order of 8 months.

Hereditary Amyloidoses

Mutations in several genes, such as transthyretin, fibrinogen, apolipoprotein A1, and apolipoprotein A2 can be responsible for hereditary amyloidosis, but by far the most common cause is variant ATTR amyloidosis (variant ATTR) caused by mutations in the transthyretin gene causing neuropathy and, often, cardiac involvement.

TTR gene mutation

The most common is the Val122Ile mutation. In a large autopsy study that included individuals with cardiac amyloidosis, the TTR Val122Ile allele was present in 3.9% of all African Americans and 23% of African Americans with cardiac amyloidosis. Penetrance of the mutation is not truly known and is associated with a late-onset cardiomyopathy that is indistinguishable from senile cardiac amyloidosis.

Pathology, Presentation, and Management of Amyloidoses

More than 100 genetic variants of TTR are associated with amyloidosis. Most present as the clinical syndrome of progressive peripheral and autonomic neuropathy. Unlike wild-type ATTR or variant ATTR Val122Ile, the features of other variant ATTR include vitreous amyloid deposits or, rarely, deposits in other organs. Cardiac involvement in variant ATTR varies by mutations and can be the presenting or indeed the only clinical feature. For example, cardiac involvement is rare in variant ATTR associated with Val30Met (a common variant in Portugal or Sweden), but it is almost universal and develops early in individuals with variant ATTR due to Thr60Ala mutation (a mutation common in Ireland).

Senile Systemic Amyloidosis (Wild-Type ATTR)

Wild-type TTR amyloid deposits are found at autopsy in about 25% of individuals >80 years of age. The prevalence of wild-type TTR deposits leading to the clinical syndrome of wild-type ATTR cardiac amyloidosis is unknown. Wild-type ATTR is a predominantly cardiac disease, and the only other significant extracardiac feature is a history of carpal tunnel syndrome, often preceding heart failure by 3 to 5 years. Extracardiac involvement is most unusual.

Both wild-type ATTR and ATTR due to Val122Ile are diseases of the >60-year age group and are often misdiagnosed as hypertensive heart disease. Wild-type ATTR has a strong male predominance, and the natural history remains poorly understood, but studies suggest a median survival of about 7 years from presentation. Recent developments in cardiac magnetic resonance (CMR), which have greatly improved detection of cardiac amyloid during life, suggest that wild-type ATTR is more common than previously thought: It accounted for 0.5% of all patients seen at the UK amyloidosis center until 2001 but now accounts for 7% of 1100 cases with amyloidosis seen since the end of 2009. There appears to be an association between wild-type ATTR and history of myocardial infarctions, G/G (Val/Val) exon 24 polymorphism in the alpha2-macroglobulin (alpha2M), and the H2 haplotype of the tau gene36; the association of tau with Alzheimer’s disease raises interesting questions as both are amyloid-associated diseases of aging.

Figure 1 http://jaha.ahajournals.org/content/1/2/e000364/F1.small.gif

ECG of a patient with cardiac AL amyloidosis showing small QRS voltages (defined as ≤6 mm height), predominantly in the limb leads and pseudoinfarction pattern in the anterior leads.

Echocardiography is characteristic. Typical findings include concentric ventricular thickening with right ventricular involvement, poor biventricular long-axis function with normal/near-normal ejection fraction and valvular thickening (particularly in wild-type or variant ATTR). Diastolic dysfunction is the earliest echocardiographic abnormality and may occur before cardiac symptoms develop. Biatrial dilatation in presence of biventricular, valvular, and interatrial septal thickening 53 is a useful clue to the diagnosis.

Figure 2 http://jaha.ahajournals.org/content/1/2/e000364/F2.medium.gif

Transthoracic echocardiogram with speckle tracking. The red and yellow lines represent longitudinal motion in the basal segments, whereas the purple and green lines represent apical motion. This shows loss of longitudinal ventricular contraction at the base compared to apex.

Biomarkers.

High-sensitivity troponin is abnormal in >90% of cardiac AL patients, and the combination of BNP/NT-proBNP plus troponin measurements is used to stage and risk-stratify patients with AL amyloidosis at diagnosis. Very interestingly, the concentration of BNP/NT-proBNP in AL amyloidosis may fall dramatically within weeks after chemotherapy that substantially reduces the production of amyloidogenic light chains. The basis for this very rapid phenomenon, which is not mirrored by changes on echocardiography or CMR, remains uncertain, but a substantial fall is associated with improved outcomes.

Cardiac Magnetic Resonance.

CMR provides functional and morphological information on cardiac amyloid in a similar way to echocardiography, though the latter is superior for evaluating and quantifying diastolic abnormalities. An advantage of CMR is in myocardial tissue characterization. Amyloidotic myocardium reveals subtle precontrast abnormalities (T1, T2), but extravascular contrast agents based on chelated gadolinium provide the key information.

Figure 3 http://jaha.ahajournals.org/content/1/2/e000364/F3.small.gif

CMR with the classic amyloid global, subendocardial late gadolinium enhancement pattern in the left ventricle with blood and mid-/epimyocardium nulling together.

Recently, the technique of equilibrium contrast CMR has demonstrated much higher extracellular myocardial volume in cardiac amyloid than any other measured disease. It is anticipated that accurate measurements of the expanded interstitium in amyloidosis will prove useful in serial quantification of cardiac amyloid burden.

Figure 4 http://jaha.ahajournals.org/content/1/2/e000364/F4.small.gif

Sequential static images from a CMR TI scout sequence. As the inversion time (TI) increases, myocardium nulls first (arrow in image 3), followed by blood afterwards (arrow in image 6), implying that there is more gadolinium contrast in the myocardium than blood—a degree of interstitial expansion such that the “myocrit” is smaller than the hematocrit.

Tissue biopsy.

To confirm amyloidosis, including familial TTR amyloidosis, the demonstration of amyloid deposition on biopsied tissues is essential. With Congo red staining, amyloid deposits show a characteristic yellow-green birefringence under polarized light. Tissues suitable for biopsy include: subcutaneous fatty tissue of the abdominal wall, skin, gastric or rectal mucosa, sural nerve, and peritendinous fat from specimens obtained at carpal tunnel surgery. Sensitivity of endoscopic biopsy of gastrointestinal mucosa is around 85%; biopsy of the sural nerve is less sensitive. It is ideal to show that these amyloid deposits are specifically immunolabeled by anti-TTR antibodies.

Serum variant TTR protein.

TTR protein normally circulates in serum or plasma as a soluble protein having a tetrameric structure [Kelly 1998, Rochet & Lansbury 2000]. Normal plasma TTR concentration is 20-40 mg/dL (0.20-0.40 mg/mL). Pathogenic mutations in TTR cause conformational change in the TTR protein molecule, disrupting the stability of the TTR tetramer, which is then more easily dissociated into pro-amyloidogenic monomers.

After immunoprecipitation with anti-TTR antibody, serum variant TTR protein can be detected by mass spectrometry. Approximately 90% of TTR variants so far identified are confirmed by this method. Mass shift associated with each variant TTR protein is indicated.

Molecular genetic testing.

TTR is the only gene in which mutations are known to cause familial TTR amyloidosis.
Identified in many individuals of different ethnic backgrounds; found in large clusters in Portugal, Sweden, and Japan.
The gene has four exons; and all the hitherto-identified mutations are in exons 2, 3, or 4.

GeneReviews designates a molecular genetic test as clinically available only if the test is listed in the GeneTests Laboratory Directory by either a US CLIA-licensed laboratory or a non-US clinical laboratory.

Molecular genetic testing of TTR by sequence analysis (may be preceded by targeted mutation analysis)
Although deletion/duplication testing is available clinically, no exonic or whole-gene deletions or duplications involving TTR have been reported to cause familial transthyretin amyloidosis.
However, with newly available deletion/duplication testing methods, it is theoretically possible that such mutations may be identified in affected individuals in whom prior testing by sequence analysis of the entire coding region was negative.
Predictive testing for at-risk asymptomatic adult family members requires prior identification of the disease-causing mutation in the family.
Prenatal diagnosis and preimplantation genetic diagnosis (PGD) for at-risk pregnancies require prior identification of the disease-causing mutation in the family.

Genetically Related (Allelic) Disorders

Familial euthyroid hyperthyroxinemia is caused by normal allelic variants in TTR, including Gly6Ser, Ala109Thr, Ala109Val, and Thr119Met (see Table 5) [Nakazato 1998, Benson 2001, Saraiva 2001]. The TTR protein binds approximately 15% of serum thyroxine. These mutations increase total serum thyroxine concentration because of their increased affinity for thyroxine, however, they increase neither free thyroxine nor free triiodothyronine. Therefore, individuals with these sequence variants develop no clinical symptoms (i.e., they are euthyroid).

Senile systemic amyloidosis (SSA; previously called senile cardiac amyloidosis) results from the pathologic deposition of wild-type TTR, predominantly in the heart. Pathologic deposits are also seen in the lungs, blood vessels, and the renal medulla of the kidneys [Westermark et al 2003]. SSA affects mainly the elderly but is rarely diagnosed during life.

Sensorimotor neuropathy and autonomic neuropathy progress over ten to 20 years. Various types of cardiac conduction block frequently appear. Cachexia is a common feature at the late stage of the disease. Affected individuals usually die of cardiac failure, renal failure, or infection.

Cardiac amyloidosis.

Cardiac amyloidosis, mainly characterized by progressive cardiomyopathy, has been reported with more than two thirds of TTR mutations. In some families with specific TTR mutations, such as Asp18Asn, Val20Ile, Pro24Ser, Ala45Thr, Ala45Ser, His56Arg, Gly57Arg, Ile68Leu, Ala81Thr, Ala81Val, His88Arg, Glu92Lys, Arg103Ser, Leu111Met, or Val122Ile, cardiomyopathy without peripheral neuropathy is a main feature of the disease.

Cardiac amyloidosis is usually late onset. Most individuals develop cardiac symptoms after age 50 years; cardiac amyloidosis generally presents with restrictive cardiomyopathy. The typical electrocardiogram shows a pseudoinfarction pattern with prominent Q wave in leads II, III, aVF, and V1-V3, presumably resulting from dense amyloid deposition in the anterobasal or anteroseptal wall of the left ventricle. The echocardiogram reveals left ventricular hypertrophy with preserved systolic function. The thickened walls present “a granular sparkling appearance.”

Among the mutations responsible for cardiac amyloidosis, Val122Ile is notable for its prevalence in African Americans. Approximately 3.0%-3.9% of African Americans are heterozygous for Val122Ile . The high frequency of Val122Ile partly explains the observation that in individuals in the US older than age 60 years, cardiac amyloidosis is four times more common among blacks than whites.

Leptomeningeal (oculoleptomeningeal) amyloidosis.

Amyloid deposition is seen in the pial and arachnoid membrane, as well as in the walls of vessels in the subarachnoid space associated with TTR mutations including Leu12Pro, Asp18Gly, Ala25Thr, Val30Gly, Ala36Pro, Gly53Glu, Gly53Ala, Phe64Ser, Tyr69His, or Tyr114Cys. Individuals with leptomeningeal amyloidosis show CNS signs and symptoms including: dementia, psychosis, visual impairment, headache, seizures, motor paresis, ataxia, myelopathy, hydrocephalus, or intracranial hemorrhage. When associated with vitreous amyloid deposits, leptomeningeal amyloidosis is known as familial oculolepto-meningeal amyloidosis (FOLMA). In leptomeningeal amyloidosis protein concentration in the cerebrospinal fluid is usually high, and gadolinium-enhanced MRI typically shows extensive enhancement of the surface of the brain, ventricles, and spinal cord.

Genotype-Phenotype Correlations.

In subsets of families with the Val30Met mutation, considerable variation in phenotypic manifestations and age of onset is observed. It is hypothesized that genetic modifiers and non-genetic factors contribute to the pathogenesis and progression of familial TTR amyloidosis. The vast majority of individuals with familial TTR amyloidosis are heterozygous for a TTR mutation. It has been clinically and experimentally demonstrated that the normal allelic variant c.416C>T (Thr119Met) has a protective effect on amyloidogenesis in individuals who have the Val30Met mutation.

Cardiac amyloidosis is caused by Asp18Asn, Val20Ile, Pro24Ser, Ala45Thr, Ala45Ser, His56Arg, Gly57Arg, Ile68Leu, Ala81Thr, Ala81Val, His88Arg, Glu92Lys, Arg103Ser, Leu111Met, or Val122Ile. Peripheral and autonomic neuropathy are absent or less evident in persons with these mutations.

Leptomeningeal amyloidosis is associated with Leu12Pro, Asp18Gly, Ala25Thr, Val30Gly, Ala36Pro, Gly53Glu, Gly53Ala, Phe64Ser, Tyr69His, or Tyr114Cys.

Penetrance.

It is generally accepted that the penetrance is much higher in individuals in endemic foci than outside of endemic foci. In Portugal, cumulative disease risk in individuals with the Val30Met mutation is estimated at 80% by age 50 and 91% by age 70 years, whereas the risk in French heterozygotes is 14% by age 50 and 50% by age 70 years. In Sweden, the penetrance is much lower: 1.7% by age 30, 5% by age 40, 11% by age 50, 22% by age 60, 36% by age 70, 52% by age 80, and 69% by age 90, respectively.

Nomenclature

The neuropathy associated with TTR mutations, now called familial TTR amyloidosis, was formerly referred to as one of the following:

Familial amyloid polyneuropathy type I (or the Portuguese-Swedish-Japanese type)
Familial amyloid polyneuropathy type II (or the Indiana/Swiss or Maryland/German type)

Prevalence

The Val30Met mutation, found worldwide, is the most widely studied TTR variant and is responsible for the well-known large foci of individuals with TTR amyloid polyneuropathy in Portugal, Sweden, and Japan. Numerous families with various non-Val30Met mutations have also been identified worldwide.

Small transthyretin (TTR) ligands as possible therapeutic agents in TTR amyloidoses.

Almeida MR, Gales L, Damas AM, Cardoso I, Saraiva MJ. Porto, Portugal.

Curr Drug Targets CNS Neurol Disord. 2005 Oct;4(5):587-96.

In transthyretin (TTR) amyloidosis TTR variants deposit as amyloid fibrils giving origin, in most cases, to peripheral polyneuropathy, cardiomyopathy, carpal tunnel syndrome and/or amyloid deposition in the eye. The amino acid substitutions in the TTR variants destabilize the tetramer, which may dissociate into non native monomeric intermediates that aggregate and polymerize in amyloid fibrils that further elongate. Since this is a multi-step process there is the possibility to impair TTR amyloid fibril formation at different stages of the process namely by tetramer stabilization, inhibition of fibril formation or fibril disruption. Based on the proposed mechanism for TTR amyloid fibril formation we discuss the action of some of the proposed TTR stabilizers such as derivatives of some NSAIDs (diflunisal, diclofenac, flufenamic acid, and derivatives) and the action of amyloid disrupters such as 4′-iodo-4′-deoxydoxorubicin (I-DOX) and tetracyclines. Among all these compounds, TTR stabilizers seem to be the most interesting since they would impair very early the process of amyloid formation and could also have a prophylactic effect.

Clusterin regulates transthyretin amyloidosis.

Lee KW, Lee DH, Son H, Kim YS, Park JY, et al. Gyeongnam National University, South Korea

Biochem Biophys Res Commun 2009;388(2):256-60. http://dx.doi.org/10.1016/j.bbrc.2009.07.166.

Clusterin has recently been proposed to play a role as an extracellular molecular chaperone, affecting the fibril formation of amyloidogenic proteins. The ability of clusterin to influence amyloid fibril formation prompted us to investigate whether clusterin is capable of inhibiting TTR amyloidosis. Here, we report that clusterin strongly interacts with wild-type TTR and TTR variants V30M and L55P under acidic conditions, and blocks the amyloid fibril formation of TTR variants. In particular, the amyloid fibril formation of V30M TTR in the presence of clusterin is reduced to level similar to wild-type TTR. We also demonstrated that clusterin is an effective inhibitor of L55P TTR amyloidosis, the most aggressive form of TTR diseases. The mechanism by which clusterin inhibits TTR amyloidosis appears to be through stabilization of TTR tetrameric structure.

Prognosis.

Cardiac amyloidosis in general has a poor prognosis, but this differs according to amyloid type and availability and response to therapy. Treatment may be classified as follows: supportive therapy (ie, modified heart-failure treatment including device therapy); therapies that suppress production of the respective amyloid fibril precursor protein (eg, chemotherapy in AL amyloidosis); and novel strategies to inhibit amyloid fibril formation or to directly target the amyloid deposits or stabilize the precursor protein (especially in ATTR with drugs such as tafamidis or diflunisal). Cardiac transplantation, although rarely feasible, can be very successful in carefully selected patients.

Reducing Amyloid Fibril Precursor Protein Production

Treatment of amyloidosis is currently based on the concept of reducing the supply of the respective amyloid fibril precursor protein. In AL amyloidosis, therapy is directed toward the clonal plasma cells using either cyclical combination chemotherapy or high-dose therapy with autologous stem cell transplantation.

The newer treatment options include bortezomib (a proteosome inhibitor)105 and the newer immunomodulatory drugs lenalidomide and pomalidomide. Bortezomib combinations appear to be especially efficient in amyloidosis with high rates of near-complete clonal responses, which appear to translate into early cardiac responses.106–108 Phase II (bortezomib in combination with cyclophosphamide or doxorubicin) and phase III (bortezomib, melphalan, and dexamethasone compared to melphalan and dexamethasone as front-line treatment) trials are underway.

AA amyloidosis is the only other type of amyloidosis in which production of the fibril precursor protein can be effectively suppressed by currently available therapies. Anti-inflammatory therapies, such as anti-tumor necrosis factor agents in rheumatoid arthritis, can substantially suppress serum amyloid A protein production, but very little experience has been obtained regarding cardiac involvement, which is very rare in this particular type of amyloidosis.

TTR is produced almost exclusively in the liver, and TTR amyloidosis has lately become a focus for novel drug developments aimed at reducing production of TTR through silencing RNA and antisense oligonucleotide therapies. ALN-TTR01, a systemically delivered silencing RNA therapeutic, is already in phase I clinical trial. Liver transplantation has been used as a treatment for variant ATTR for 20 years, to remove genetically variant TTR from the plasma. Although this is a successful approach in ATTR Val30Met, it has had disappointing results in patients with other ATTR variants, which often involve the heart. The procedure commonly results in progressive cardiac amyloidosis through ongoing accumulation of wild-type TTR on the existing template of variant TTR amyloid. The role of liver transplantation in non-Val30Met–associated hereditary TTR amyloidosis thus remains very uncertain.

Inhibition of Amyloid Formation

Amyloid fibril formation involves massive conformational transformation of the respective precursor protein into a completely different form with predominant β-sheet structure. The hypothesis that this conversion might be inhibited by stabilizing the fibril precursor protein through specific binding to a pharmaceutical has lately been explored in TTR amyloidosis. A key step in TTR amyloid fibril formation is the dissociation of the normal TTR tetramer into monomeric species that can autoaggregate in a misfolded form. In vitro studies identified that diflunisal, a now little used nonsteroidal anti-inflammatory analgesic, is bound by TTR in plasma, and that this enhances the stability of the normal soluble structure of the protein. Studies of diflunisal in ATTR are in progress. Tafamidis is a new compound without anti-inflammatory analgesic properties that has a similar mechanism of action. Tafamidis has just been licensed for neuropathic ATTR, but its role in cardiac amyloidosis remains uncertain, and clinical trial results are eagerly awaited. Higher-affinity “superstabilizers” are also in development.

Conclusion

Cardiac amyloidosis remains challenging to diagnose and to treat. Key “red flags” that should raise suspicion include clinical features indicating multisystem disease and concentric LV thickening on echocardiography in the absence of increased voltage on ECG; the pattern of gadolinium enhancement on CMR appears to be very characteristic. Confirmation of amyloid type is now possible in most cases through a combination of immunohistochemistry, DNA analysis, and proteomics. A variety of novel specific therapies are on the near horizon, with potential to both inhibit new amyloid formation and enhance clearance of existing deposits.

Circulation 2012; 126:1286-1300 http://dx.doi.org/10.1161/CIRCULATIONAHA.111.078915

Future Prospects

Jeffery W. Kelly, the former Dean of Graduate Studies (2000-2008) and Vice President of Academic Affairs (2000-2006), currently is the Chairman of Molecular and Experimental Medicine and the Lita Annenberg Hazen Professor of Chemistry within the Skaggs Institute of Chemical Biology at The Scripps Research Institute in La Jolla, California.

The work on folding proteins by the Kelly Group focuses on

[1] understanding protein misfolding and aggregation and on developing both chemical

[2] and biological strategies

[3] to ameliorate diseases caused by protein misfolding and/or aggregation.

Besides studying the structural and energetic basis behind protein folding, his laboratory also studies the etiology of neurodegenerative diseases linked to protein aggregation, including Alzheimer’s disease, Parkinson’s Disease, and the familial gelsolin and transthyretin-based amyloidoses–publishing over 250 peer-reviewed papers in this area to date. He has also provided insight into genetic diseases associated with loss of protein function, such as lysosomal storage diseases.

Kelly has cofounded three biotechnology companies, FoldRx Pharmaceuticals (with Susan Lindquist), now owned by Pfizer, Proteostasis Therapeutics, Inc. (with Andrew Dillin and Richard Morimoto) (a private corporation) and Misfolding Diagnostics (with Xin Jiang and Justin Chapman; a private corporation). The Kelly laboratory discovered the first regulatory agency-approved drug that slows the progression of a human amyloid disease using a structure-based design approach. This drug, now called Tafamidis or Vyndaqel, slowed the progression of familial amyloid polyneuropathy in an 18 month placebo controlled trial and in an 18 month extension study sponsored by FoldRx Pharmaceuticals (acquired by Pfizer in 2010). Vyndaqel or Tafamidis was approved for the treatment of Familial amyloid Polyneuropathy by the European Medicines Agency in late 2011. Kelly also discovered that diflunisal kinetically stabilizes transthyretin, enabling a placebo controlled clinical trial with it to ameliorate familial amyloid polyneuropathy–the results of which will be announced in 2013. Proteostasis Therapeutics, Inc. is developing first-in-class drugs that adapt the proteostasis network to ameliorate both loss-of-function misfolding diseases and gain-of-toxic function diseases linked to protein aggregation.

In addition to discovering the first drug that slows the progression of a human amyloid disease, the Kelly Laboratory is credited with demonstrating that transthyretin conformational changes alone are sufficient for amyloidogenesis, discovering the first example of functional amyloid in mammals, making major contributions toward understanding β-sheet folding, discovering the “enhanced aromatic sequon”–sequences that are more efficiently glycosylated by cells and sequences which stabilize the proteins that they are incorporated into as a consequence of N-glycosylation and was corresponding author on and contributed some of the key experimental data demonstrating that altering cellular proteostasis capacity has the potential to alleviate protein misfolding and aggregation diseases.

http://www.scripps.edu/kelly/research.php?a=l&cid=3&lsc=t&lscid=23

http://www.scripps.edu/kelly/images/tsri_logo.gif

http://www.scripps.edu/kelly/photos/fig01.jpg

Native state kinetic stabilization as a strategy to ameliorate protein misfolding diseases: a focus on the transthyretin amyloidoses. Johnson SM, Wiseman RL, Sekijima Y, Green NS, Adamski-Werner SL, Kelly JW. http://www.ncbi.nlm.nih.gov/pubmed/16359163

Small molecule-mediated protein stabilization inside or outside of the cell is a promising strategy to treat protein misfolding/misassembly diseases. Herein we focus on the transthyretin (TTR) amyloidoses and demonstrate that preferential ligand binding to and stabilization of the native state over the dissociative transition state raises the kinetic barrier of dissociation (rate-limiting for amyloidogenesis), slowing and in many cases preventing TTR amyloid fibril formation. Since T119M-TTR subunit incorporation into tetramers otherwise composed of disease-associated subunits also imparts kinetic stability on the tetramer and ameliorates amyloidosis in humans, it is likely that small molecule-mediated native state kinetic stabilization will also alleviate TTR amyloidoses.

Energetic characteristics of the new transthyretin variant A25T may explain its atypical central nervous system pathology.

Sekijima Y, Hammarström P, Matsumura M, Shimizu Y, Iwata M, Tokuda T, Ikeda S, Kelly JW.

Lab Invest. 2003 Mar;83(3):409-17. http://www.ncbi.nlm.nih.gov/pubmed/12649341

Transthyretin (TTR) is a tetrameric protein that must misfold to form amyloid fibrils. Misfolding includes rate-limiting tetramer dissociation, followed by fast tertiary structural changes that enable aggregation. Amyloidogenesis of wild-type (WT) TTR causes a late-onset cardiac disease called senile systemic amyloidosis. The aggregation of one of > 80 TTR variants leads to familial amyloidosis encompassing a collection of disorders characterized by peripheral neuropathy and/or cardiomyopathy. Prominent central nervous system (CNS) impairment is rare in TTR amyloidosis. Herein, we identify a new A25T TTR variant in a Japanese patient who presented with CNS amyloidosis at age 42 and peripheral neuropathy at age 44. The A25T variant is the most destabilized and fastest dissociating TTR tetramer published to date, yet, surprising, disease onset is in the fifth decade. Quantification of A25T TTR in the serum of this heterozygote reveals low levels relative to WT, suggesting that protein concentration influences disease phenotype. Another recently characterized TTR CNS variant (D18G TTR) exhibits strictly analogous characteristics, suggesting that instability coupled with low serum concentrations is the signature of CNS pathology and protects against early-onset systemic amyloidosis. The low A25T serum concentration may be explained either by impaired secretion from the liver or by increased clearance, both scenarios consistent with A25T’s low kinetic and thermodynamic stability. Liver transplantation is the only known treatment for familial amyloid polyneuropathy. This is a form of gene therapy that removes the variant protein from serum preventing systemic amyloidosis. Unfortunately, the choroid plexus would have to be resected to remove A25T from the CSF-the source of the CNS TTR amyloid. Herein we demonstrate that small-molecule tetramer stabilizers represent an attractive therapeutic strategy to inhibit A25T misfolding and CNS amyloidosis. Specifically, 2-[(3,5-dichlorophenyl)amino]benzoic acid is an excellent inhibitor of A25T TTR amyloidosis in vitro.

Prevention of Transthyretin Amyloid Disease by Changing Protein Misfolding Energetics

Per Hammarström*, R. Luke Wiseman*, Evan T. Powers, Jeffery W. Kelly†

Science 31 Jan 2003; 299(5607):713-716 http://dx.doi.org/10.1126/science.1079589

Genetic evidence suggests that inhibition of amyloid fibril formation by small molecules should be effective against amyloid diseases. Known amyloid inhibitors appear to function by shifting the aggregation equilibrium away from the amyloid state. Here, we describe a series of transthyretin amyloidosis inhibitors that functioned by increasing the kinetic barrier associated with misfolding, preventing amyloidogenesis by stabilizing the native state. The trans-suppressor mutation, threonine 119 → methionine 119, which is known to ameliorate familial amyloid disease, also functioned through kinetic stabilization, implying that this small-molecule strategy should be effective in treating amyloid diseases.

R104H may suppress transthyretin amyloidogenesis by thermodynamic stabilization, but not by the kinetic mechanism characterizing T119 interallelic trans-suppression.

Sekijima Y, Dendle MT, Wiseman RL, White JT, D’Haeze W, Kelly JW.

Amyloid. Jun 2006;13(2):57-66. http://www.ncbi.nlm.nih.gov/pubmed/16911959

The tetrameric protein transthyretin (TTR) forms amyloid fibrils upon dissociation and subsequent monomer misfolding, enabling misassembly. Remarkably, the aggregation of one of over 100 destabilized TTR variants leads to familial amyloid disease. It is known that trans-suppression mediated by the incorporation of T119M subunits into tetramers otherwise composed of the most common familial variant V30M, ameliorates disease by substantially slowing the rate of tetramer dissociation, a mechanism referred to as kinetic stabilization of the native state. R104H TTR has been reported to be non-pathogenic, and recently, this variant has been invoked as a trans-suppressor of amyloid fibril formation. Here, we demonstrate that the trans-suppression mechanism of R104H does not involve kinetic stabilization of the tetrameric structure, instead its modest trans-suppression most likely results from the thermodynamic stabilization of the tetrameric TTR structure. Thermodynamic stabilization increases the fraction of tetramer at the expense of the misfolding competent monomer decreasing the ability of TTR to aggregate into amyloid fibrils. As a consequence of this stabilization mechanism, R104H may be capable of protecting patients with modestly destabilizing mutations against amyloidosis by slightly lowering the overall population of monomeric protein that can misfold and form amyloid.