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Archive - May 14, 2015

Structure of Surface Protein of Very Large Mimiviruses Identified, May Provide New Clues to This Highly Mysterious Virus

Researchers have discovered the structure of a key protein on the surface of an unusually large virus called the mimivirus, aiding efforts to determine its hosts and unknown functions. The mimivirus was initially thought to be a bacterium because it is much larger than most viruses. It was isolated by French scientists in 1992, but was not confirmed to be a virus until 2003. In the laboratory, the virus has been studied while infecting amoebas, but its natural hosts in the wild and many other details about the virus remain unknown, said Dr. Michael Rossmann, Purdue University's Hanley Distinguished Professor of Biological Sciences. He led a team of researchers who discovered the structure of a key, enzyme-like protein called R135, which is contained in fibers on the outer surface of the virus. The structure of R135 is similar to an enzyme called aryl alcohol oxidase, which is found in a fungus and is involved in biodegrading lignin in plant cell walls. "This could tell us something about the mimivirus's natural hosts," Dr. Rossmann said. "We think there must be another host, something different than amoebas, and that this enzyme helps the virus get into this host. Perhaps R135 participates in the degradation of lignin so that the virus can enter a host such as lignin-containing algae." Also suggesting the possibility of alternative hosts is the recent discovery that mimivirus has been found to be abundant in oysters. Antibodies against mimivirus have been found in humans, and the virus has been discovered inside specialized cells in humans called macrophages, but whether it actually infects people is not known. "I wouldn't say it infects humans, but it can propagate in humans because macrophages take up this virus and it can propagate in these," said Dr.

Maternal Famine in First 10 Weeks of Gestation Adversely Affects Embryo’s DNA Methylation Status, Leading to Suppression of Genes for Growth, Development, and Metabolism As Adult

Researchers at Columbia University's Mailman School of Public Health and at Leiden University in the Netherlands found that children whose mothers were malnourished at famine levels during the first 10 weeks of pregnancy had changes in DNA methylation known to suppress genes involved in growth, development, and metabolism documented at age 59. This is the first study to look at prenatal nutrition and genome-wide DNA patterns in adults exposed to severe under-nutrition at different periods of gestation. The findings were published online on May 5, 2015 in an open-access article in the International Journal of Epidemiology. Tha article is titled “Early Gestation As the Critical Time-Window for Changes in the Prenatal Environment to Affect the Adult Human Blood Methylome.” The study evaluated how famine exposure -- defined as 900 calories daily or less -- during the Dutch Hunger Winter of 1944-1945 (see image) affected genome-wide DNA methylation levels. The researchers also studied the impact of short-term exposure, pre-conception and post-conception. The study used blood samples of 422 individuals exposed to the famine at any time during gestation and 463 controls without prenatal famine exposure. The authors examined individuals born between February 1945 and March 1946 whose mothers were exposed to the famine during or immediately preceding pregnancy, individuals conceived between March and May 1945 at the time of extreme famine, and controls born in the same institutions whose mothers did not experience famine while pregnant, as well as sibling controls who were also not exposed to famine in pregnancy. The findings show associations between famine exposure during weeks 1-10 of gestation and DNA changes, but not later in pregnancy.

Free Extracellular miRNA Functionally Targets Cells by Targeting Exosomes from Their Companion Cells

A Yale-led research team has described a novel pathway for the delivery of microRNA (miRNA), the tiny RNA molecules that can move between cells to regulate gene expression. The study was published online on April 29, 2015 in the open-access journal PLOS ONE. Scientists had previously described how miRNA transfers genetic regulatory information from cell to cell within protective nano-vesicles (sacs) known as exosomes. In this study, the Yale team — led by Professorof Medicine (Immunology) Philip Askenase (photo), M.D., in collaboration with visiting Professor Krzysztof Bryniarski from Jagiellonian University in Krakow, Poland — examined how miRNAs from mouse immune T cells are delivered independently of these exosome vesicles. Although such “free” extracellular RNA, or exRNA, is the dominant form of RNA in the circulation, the function of exRNA was not known. However, the researchers discovered that exRNA can associatewith exosomes from companion cells of the targeted cells (in this case, companion immune system B cells) to transfer the genetic messages via specific structures (antigens) on the final targeted cell. The findings are significant, say the researchers, because they show, not only how freely circulating miRNA transfers between cells, but also how it can influence the function of targeted cells in an antigen-specific way. The research provides a model for future study of miRNA information transfer between cells, and as a basis for the potential development of unique RNA genetic therapies for human diseases, including allergy, autoimmunity, and even cancer. Other authors of the PLOS ONE article include Wlodzimierz Ptak, Katarzyna Nazimek, Emilia Martin, Marian Szczepanik, and Marek Sanak. The Yale press release for this news was written by Ziba Kashef.

New Study Elucidates Genetic Differences Between Morning Fruit Flies (“Larks”) and Evening Fruit Flies (‘Owls”); Likely Clues to Human Differences Also

A new study by geneticists from the University of Leicester has for the first time identified the genetic clues behind what makes you a ‘lark’ or an ‘owl’. Based on analysis of a fruit fly, the scientists have discovered nearly 80 genes associated with “morningness” and “eveningness.” Researcher Dr. Eran Tauber, one of the three authors of the study, published online on May 8, 2015 in an open-access article in Frontiers in Neurology, said: “Most people find that their performance is at peak at specific times of day. A great variation in this diurnal preference is found, from early risers ‘larks’ to late night ‘owls.’ The impact of this preference (‘chronotype’) on health and behaviour is well documented, but the molecular basis is largely unknown. The article is titled “Gene Expression Associated with Early and Late Chronotypes in Drosophila melanogaster.” “In this new study, we have used fruit flies, whose gene clocks are very similar to human, to get a first insight into the molecular basis of ‘morningness/eveningness’ preference. Because this genetic system is so similar between insects and human, there is a good chance that some of the genes that we have identified in flies, would be also important for diurnal preference in humans. Most of these genes are present in the mammalian genome and would therefore be useful starting points for research in human. For example, a relatively large number of genes were associated with a molecular signalling pathway called MAPK which is also present in human and is implicated in the development of many cancers.” Dr. Tauber, Lecturer in Molecular Evolution at the University of Leicester, worked with Dr. Ezio Rosato and Professor Bambos Kyriacou in the Department of Genetics. Their work was funded by the BBSRC. Dr.