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Archive - Nov 16, 2012

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Class of Small RNA Molecules Protects Germ Cells from Damage

Passing one's genes on to the next generation is a mark of evolutionary success. So it makes sense that the body would work to ensure that the genes the next generation inherits are exact replicas of the originals. New research by biologists at the University of Pennsylvania School of Veterinary Medicine (Penn Vet) has now identified one way the body does exactly that. This protective role is fulfilled in part by a class of small RNA molecules called pachytene piwi-interacting RNAs, or piRNAs. Without them, germ cell development in males comes to a halt. Because these piRNAs play such an important role in allowing sperm to develop normally, the research indicates that defects in these molecules or the molecules with which they interact may be responsible for some cases of male infertility. Dr. Jeremy Wang, an associate professor of developmental biology and director of the Center for Animal Transgenesis and Germ Cell Research at Penn Vet, and Dr. Ke Zheng, a postdoctoral researcher in Dr. Wang's lab, authored the study, which appeared November 15, 2012 in PLOS Genetics. Scientists know of 8 million different piRNAs in existence; they are the most abundant type of small non-coding RNA. The molecule piRNA gets its name because it forms complexes with piwi proteins. Earlier work had indicated that these piwi-piRNA complexes suppress the activity of transposable elements or "jumping genes," which are stretches of DNA that can change position and cause potentially damaging genetic mutations. These sequences are also known as transposons. "There are about 50 human diseases caused by transposable elements, so it's important for the body to have a way to try to repress them," Dr. Wang said.

Gene Variant Distinguishes Early Birds from Night Owls; Helps Predict Time of Day One Is Likely to Die

Many of the body's processes follow a natural daily rhythm or so-called circadian clock. There are certain times of the day when a person is most alert, when blood pressure is highest, and when the heart is most efficient. Several rare gene mutations have been found that can adjust this clock in humans, responsible for entire families in which people wake up at 3 a.m. or 4 a.m. and cannot stay up much after 8 at night. Now new research has, for the first time, identified a common gene variant that affects virtually the entire population, and which is responsible for up to an hour a day of your tendency to be an early riser or night owl. Furthermore, this new discovery not only demonstrates this common polymorphism influences the rhythms of people's day-to-day lives -- it also finds this genetic variant helps determine the time of day a person is most likely to die. The surprising findings, which appear in the September 2012 issue of the Annals of Neurology, could help with scheduling shift work and planning medical treatments, as well as in monitoring the conditions of vulnerable patients. "The internal 'biological clock' regulates many aspects of human biology and behavior, such as preferred sleep times, times of peak cognitive performance, and the timing of many physiological processes. It also influences the timing of acute medical events like stroke and heart attack," says first author Andrew Lim, M.D., who conducted the work as a postdoctoral fellow in the Department of Neurology at Beth Israel Deaconess Medical Center (BIDMC) in Boston. "Previous work in twins and families had suggested that the lateness or earliness of one's clock may be inherited and animal experiments had suggested that the lateness or earliness of the biological clock may be influenced by specific genes," adds Dr.

Vitamin D3 Deficiency Linked to Type 1 Diabetes

A study led by researchers from the University of California, San Diego School of Medicine has found a correlation between vitamin D3 serum levels and subsequent incidence of type 1 diabetes. The six-year study of blood levels of nearly 2,000 individuals suggests a preventive role for vitamin D3 in this disease. The research appears in the December 2012 issue of Diabetologia, a publication of the European Association for the Study of Diabetes (EASD). "Previous studies proposed the existence of an association between vitamin D deficiency and risk of type 1 diabetes, but this is the first time that the theory has been tested in a way that provides the dose-response relationship," said Cedric Garland, DrPH, FACE, professor in UCSD's Department of Family and Preventive Medicine. This study used samples from millions of blood serum specimens frozen by the Department of Defense Serum Registry for disease surveillance. The researchers thawed and analyzed 1,000 samples of serum from healthy people who later developed type 1 diabetes and 1,000 healthy controls whose blood was drawn on or near the same date but who did not develop type 1 diabetes. By comparing the serum concentrations of the predominant circulating form of vitamin D – 25-hydroxyvitamin D (25(OH)D) – investigators were able to determine the optimal serum level needed to lower an individual's risk of developing type 1 diabetes. Based mainly on results of this study, Dr. Garland estimates that the level of 25(OH)D needed to prevent half the cases of type 1 diabetes is 50 ng/ml. A consensus of all available data indicates no known risk associated with this dosage. "While there are a few conditions that influence vitamin D metabolism, for most people, 4000 IU per day of vitamin D3 will be needed to achieve the effective levels," Dr. Garland suggested.

Pig Genome Sequenced

An international scientific collaboration that includes two Kansas State University researchers is bringing home the bacon when it comes to potential animal and human health advancements, thanks to successfully mapping the genome of the domestic pig. The sequenced genome gives researchers a genetic blueprint of the pig. It includes a complete list of DNA and genes that give pigs their traits like height and color. Once all of the genetic information is understood, scientists anticipate improvements to the animal's health as well as human health, as pigs and humans share similar physiologies. "With the sequenced genome we have a better blueprint than we had before about the pig's genetics and how those genetic mechanisms work together to create (characteristics), such as the unique merits in disease resistance," said Dr. Yongming Sang, research assistant professor of anatomy and physiology at Kansas State University. For three years, Dr. Sang worked on the genome sequencing project with Dr. Frank Blecha, associate dean for the College of Veterinary Medicine and university distinguished professor of anatomy and physiology. A report of the international study appears as the cover story of the November 15 issue of the journal Nature. The sequencing effort was led by the Swine Genome Sequencing Consortium. Researchers with the consortium inviting Drs. Sang and Blecha to work on the project because of their expertise and published studies on the antimicrobial peptides and interferons that pigs use to genetically defend themselves against disease. Drs. Sang and Blecha focused on these two families of immune genes, looking for gene duplications and gene-family expansions throughout the pig's 21,640 protein-coding genes, in an effort to help scientists with future pig-related research. Dr.