Larry H. Bernstein, MD, FCAP, Curator
http://pharmaceuticalintelligence.com/7/7/2014/Bzzz! Are fruitflies like us?
We are following closely the developments in genomics that have had a progression since the Double-Helix dogma served the Nobel Prize to Watson and Crick, and that achievement led to the completion of a provisional Human Genome at the birth of the 21st century. Since then there has been exploration of cellular regulation, signaling pathways, and protein-protein as well as protein membrane interactions in eukaryotes. But we can go further back prior to the double-helix and remind ourselves of the huge contributions that led up to the double helix. This was a time of great research that set the tone for what is now called molecular biology. We associate the work with the genetic studies of Thomas Hunt Morgan on the fruit fly. There may yet be a new chapter that is stradling the gap between DNA, RNA and transcription turning toward a deeper understanding of gene expression and organ specificities. Is it a new beginning? There is certainly going to be a deeper understanding of the several roles of RNA as well as proteins.
The Gateway Opens
THOMAS HUNT MORGAN AT COLUMBIA UNIVERSITY
Genes, Chromosomes, and the Origins of Modern Biology
2000 recipent of Nobel Prize in Medicine
University Professor & Kavli Professor of Brain Science,
Co-director, Mind Brain Behavior Initiative
Director, The Kavli Institute for Brain Science
Senior Investigator, Howard Hughes Medical Institute
Columnia University
When future historians turn to examine the major intellectual accomplishments of the twentieth century, they will undoubtedly give a special place to the extraordinary achievements in biology, achievements that have revolutionized our understanding of life’s processes and of disease. Important intimations of what was to happen in biology were already apparent in the second half of the nineteenth century. Darwin had delineated the evolution of animal species, Mendel had discovered some basic rules about inheritance, and Weissman, Roux, Driesch, de Vries, and other embryologists were beginning to decipher how an organism develops from a single cell. What was lacking at the end of the nineteenth century, however, was an overarching sense of how these bold advances were related to one another.
The insight that unified these three fields- heredity, evolution, and development- and set biology on the course toward its current success came only at the beginning of the twentieth century. It derived from the discovery that the gene, localized to specific positions on the chromosome, was at once the unit of Mendelian heredity, the driving force for Darwinian evolution, and the control switch for development. This remarkable discovery can be traced directly to one person and to one institution: Thomas Hunt Morgan and Columbia University. Much as Darwin’s insights into the evolution of animal species first gave coherence to nineteenth-century biology as a descriptive science, Morgan’s findings about genes and their location on chromosomes helped transform biology into an experimental science.
“ aware that abstract thinking, remote from, and even antagonistic to the study of nature, leads easily into dogma, taboos and fettering of free thinking because it does not carry its own corrective, the recourse to factual evidence. The scientist, therefore, with all respect for the many facets of the human mind, is more impressed by the revolutions in thinking brought about by great factual discoveries, which by their very nature lead to generalizations which change at once the outlook of many, if not all, lines of thought.”
. . . . the rise and development of genetics to mature age is another instance of an all-comprising and all-affecting generalization based upon an overwhelming body of integrated facts, . . . [and] will rank in the history of science with such other great events ..”
–Richard B. Goldschmidt, The Impact of Genetics Upon Science (1950)
Even more important, Morgan’s discoveries made it possible to address a series of questions regarding the function and structure of genes. What is their chemical nature? How do genes duplicate themselves? What goes wrong when genes mutate? How do genes provide the basis for understanding genetic disease? How do genes determine the properties of cells, the development of organisms, and the course of evolution?
July 7, 2014
This investigation of the fruit fly’s transcriptome—the complete collection of the genome’s RNA—unearthed thousands of new genes, transcripts, and proteins
Scientists have teased another level of information out of the genome. This time, the new insights were developed from studies of the fruit fly’s transcriptome. This knowledge will give pathologists another channel of information that may be useful in developing assays to support more precise diagnosis and therapeutic decisions.
The findings were published in a recent issue of Nature. The study focused on the transcriptome—a complete collection of the genome’s RNA—of the common fruit fly−Drosophila melangogaster.
Why Studies of the Fruit Fly Are Useful
The fruit fly has been used as a genetics model to study human genetics for more than a 100 years. Not only are they easy to care for and work with, but they share 75% of the same genes as humans. Today, the fruit fly genome has emerged as a critical tool tor understanding human biology and disease, by providing an understanding of genes and life processes that are conserved over extensive evolutionary changes.
The research consortium included 41 researchers from 11 universities and institutes that are members of the National Human Genome Research Institute’s Model Organism Encyclopedia of DNA Elements, called modENCODE for short. This project used state-of-the-art gene sequencing to study all of the expressed RNAs produced by a genome in greater detail than ever before accomplished.
RNA Sequenced in Diverse Tissues at Different Stages of Development
RNA was sequenced at different stages of development, in diverse tissues, in cells growing in culture, and in flies stressed by environmental contaminants, stated a IU press release issued by Indiana University Bloomington (IUB).
The modENCODE study revealed that the fruit fly genome is far more complex than previously suspected. These new findings suggest that this also may be true for the genomes of higher animals. Specifically, the researchers found that:
- a small set of genes in the nervous system is responsible for much of the complexity;
- long regulatory and antisense RNA (asRNA), a single-stranded RNA complementary to a messenger RNA transcribed within a cell, are prominent during gonadal development;
- splicing factors, proteins involved in controlling maturation of RNAs, are themselves spliced in complex ways; and,
- the fruit fly transcriptome undergoes major changes in response toenvironmental stressors.
How Study of Fruit Fly RNA Benefits Human Genome Research
“The modENCODE work is intended to provide a new baseline for research using Drosophila,” declared Peter Cherbas, Ph.D., an IUB Professor Emeritus of Biology and one of 10 IUB researchers who served as co-authors of the study. “The goal is to provide researchers working on particular processes with much of the detailed background information they would otherwise need to collect for themselves.
Click here for photo
Peter Cherbas, Ph.D. (pictured), Professor Emeritus of Biology at Indiana University Bloomington, says that the modENCORE study of the fruit fly’s complete RNA answered a lot of questions about the genome of organisms, but raised even more questions that science will want to answer. (Photo copyright Indiana University Bloomington.)
“As usual in science, we’ve answered a number of questions and raised even more,” observed Cherbas. “For example, we identified 1,468 new genes, of which 536 were found to reside in previously uncharacterized gene-free zones.”
“We think these results could influence gene regulation research in all animals,” added Thom Kaufman, Ph.D., IUB Distinguished Professor of Biology who also co-authored the study. “This exhaustive study also identified a number of phenomena previously reported only in mammals, and that alone is really telling about the versatility of Drosophila melanogaster as a model organism. The new work provides a number of new potential uses for this powerful model system,” he stressed.
Click here for photo
Thom Kaufman, Ph.D. (pictured), Indiana University Bloomington Distinguished Professor of Biology, says that the modENCORE study provides a powerful model for studying gene regulation in all organisms. (Photo copyright Indiana University Bloomington.)
Impact of Environmental Stressors on Gene Expression
Both Kaufman and Cherbas cited perturbation experiments that identified genes and transcripts. The new genes were identified after subjecting adult fruit flies to heat and cold shock, then exposing them to heavy metals, caffeine and the herbicide paraquat. Fruit fly larvae were treated with heavy metals, caffeine, ethanol, or the insecticide rotenone.
These environmental stressors generated small changes in the expression level of thousands of genes. One treatment experiment resulted in four newly modeled genes being expressed altogether differently, noted the researchers. Perturbation experiments, in fact, revealed a total of 5,249 transcript models for 811 genes.
In fact, the findings from these perturbation experiments mirror similar findings made following the 2010 British Petroleum Deepwater Horizon oil spill in the Gulf of Mexico. Researchers studying the impact on marsh fishes found that, similar to the fruit flies, these fish responded to chronic hydrocarbon exposure with a number of expressions beyond the heat shock pathway. These expressions included the down regulation of genes encoding eggshell and yolk proteins.
The response overlap between species indicates that the modENCODE consortium may have identified a conserved metazoan [animal] stress response that enhances metabolism and suppresses genes involved in reproduction.
What This Means for Pathologists and Laboratory Professionals
This study is significant for pathologists and medical laboratory professionals because it peels away another layer of information encoded in DNA and RNA. The findings of this study also show how genomic knowledge is moving to the next level in the quest to understand the origins of disease.
—by Patricia Kirk
Study of complete RNA collection of fruit fly uncovers unprecedented complexity
IU plays key role in consortium; 1,468 new genes discovered March 17, 2014
BLOOMINGTON, Ind. — Scientists from Indiana University are part of a consortium that has described the transcriptome of the fruit fly Drosophila melanogaster in unprecedented detail, identifying thousands of new genes, transcripts and proteins.
In the new work, published Sunday in the journal Nature, scientists studied the transcriptome — the complete collection of RNAs produced by a genome — at different stages of development, in diverse tissues, in cells growing in culture, and in flies stressed by environmental contaminants. To do so, they used contemporary sequencing technology to sequence all of the expressed RNAs in greater detail than ever before possible.
The paper shows that the Drosophila genome is far more complex than previously suspected and suggests that the same will be true of the genomes of other higher organisms. The paper also reports a number of novel, particular results: that a small set of genes used in the nervous system are responsible for a disproportionate level of complexity; that long regulatory and so-called “antisense” RNAs are especially prominent during gonadal development; that “splicing factors” (proteins that control the maturation of RNAs by splicing) are themselves spliced in complex ways; and that the Drosophila transcriptome undergoes large and interesting changes in response to environmental stresses.
The importance of Drosophila melanogaster as a model system cannot be overstated. Using it, the mechanisms of heredity were worked out about 100 years ago. Today, as biologists have developed increasing appreciation of how well genes and critical life processes are conserved over long evolutionary distances, flies have emerged as critical tools for understanding human biology and disease. Drosophila research is an area that has long had associations with IU, beginning with Nobel Laureate Herman J. Muller.
IU has 10 co-authors on the paper from the IU Bloomington College of Arts and Sciences’ Department of Biology and the university’s Center for Genomics and Bioinformatics. They are included among the 41 co-authors from 11 universities and institutes that are members of the National Human Genome Research Institute’s Model Organism Encyclopedia of DNA Elements project, or modENCODE. Among the IU co-authors are Professor Emeritus of Biology Peter Cherbas, who helped manage the expansive project, and Distinguished Professor of Biology Thom Kaufman, who helped oversee design of the project and the production of biological samples.
“The modENCODE work is intended to provide a new baseline for research using Drosophila,” Cherbas said. “The goal is to provide researchers working on particular processes with much of the detailed background information they would otherwise need to collect for themselves.
“As usual in science, we’ve answered a number of questions and raised even more. For example, we identified 1,468 new genes, of which 536 were found to reside in previously uncharacterized gene-free zones.”
“We think these results could influence gene regulation research in all animals,” Kaufman said. “This exhaustive study also identified a number of phenomena previously reported only in mammals, and that alone is really telling about the versatility of Drosophila melanogaster as a model organism. The new work provides a number of new potential uses for this powerful model system.”
An example they pointed to was the perturbation experiments that identified new genes and transcripts. New genes were identified in experiments where adults were challenged with heat shock, cold shock, exposure to heavy metals, the drug caffeine and the herbicide paraquat, while larvae were treated with heavy metals, caffeine, ethanol or the insecticide rotenone.
Those environmental stresses resulted in small changes in expression level at thousands of genes; and in one treatment, four newly modeled genes were expressed altogether differently. In total, 5,249 transcript models for 811 genes were revealed only under perturbed conditions.
As did the flies in this new research, scientists who studied the Deepwater Horizon incident in the Gulf of Mexico found that marsh fishes responding to chronic hydrocarbon exposure had a number of expressional responses beyond the heat shock pathway, including the down regulation of genes encoding eggshell and yolk proteins as did the flies. To see this response overlap across phyla means the consortium may have identified a conserved metazoan stress response involving enhanced metabolism and the suppression of genes involved in reproduction.
Indiana University co-authors with Cherbas and Kaufman were co-first author Robert Eisman, Justen Andrews, Lucy Cherbas, Brian D. Eads, David Miller, Keithanne Mockaitis, Johnny Roberts and Dayu Zhang. All were associated with the Department of Biology and/or the Center for Genomics and Bioinformatics.
“Diversity and dynamics of the Drosophila transcriptome,” published March 16 in the journal Nature, also included 31 other co-authors whose affiliations were with the University of California, Berkeley; Lawrence Berkeley National Laboratory; University of Connecticut Health Center; Cold Spring Harbor Laboratory; Sloan-Kettering Institute; National Institute of Diabetes and Digestive and Kidney Diseases; RIKEN Yokohama Institute (Japan); Harvard Medical School; and Howard Hughes Medical Institute.
Antisense RNA
From Wikipedia, the free encyclopedia
Antisense RNA (asRNA) is a single-stranded RNA that is complementary to a messenger RNA (mRNA) strand transcribed within a cell. Some authors have used the term micRNA (mRNA-interfering complementary RNA) to refer to these RNAs but it is not widely used.[1]
Antisense RNA may be introduced into a cell to inhibit translation of a complementary mRNA by base pairing to it and physically obstructing the translation machinery.[2] [3] This effect is therefore stoichiometric. An example of naturally occurring mRNA antisense mechanism is the hok/sok system of the E. coli R1 plasmid. Antisense RNA has long been thought of as a promising technique for disease therapy; the only such case to have reached the market is the drug fomivirsen. One commentator has characterized antisense RNA as one of “dozens of technologies that are gorgeous in concept, but exasperating in [commercialization]”.[4] Generally, antisense RNA still lack effective design, biological activity, and efficient route of administration.[5]
Historically, the effects of antisense RNA have often been confused with the effects of RNA interference (RNAi), a related process in which double-stranded RNA fragments called small interfering RNAs trigger catalytically mediated gene silencing, most typically by targeting the RNA-induced silencing complex (RISC) to bind to and degrade the mRNA. Attempts to genetically engineer transgenic plants to express antisense RNA instead activate the RNAi pathway, although the processes result in differing magnitudes of the same downstream effect; gene silencing. Well-known examples include the Flavr Savr tomato and two cultivars of ringspot-resistant papaya.[6][7]
Transcription of longer cis-antisense transcripts is a common phenomenon in the mammalian transcriptome.[8] Although the function of some cases have been described, such as the Zeb2/Sip1 antisense RNA, no general function has been elucidated. In the case of Zeb2/Sip1,[9] the antisense noncoding RNA is opposite the 5′ splice site of an intron in the 5’UTR of the Zeb2 mRNA. Expression of the antisense ncRNA prevents splicing of an intron that contains a ribosome entry site necessary for efficient expression of the Zeb2 protein. Transcription of long antisense ncRNAs is often concordant with the associated protein-coding gene,[10] but more detailed studies have revealed that the relative expression patterns of the mRNA and antisense ncRNA are complex.[11][12]
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