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.
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