Xist marks the spot: How an RNA molecule silences the X chromosome

In one of the mysteries of mammalian development, every cell in the early female embryo shuts down one of its two copies of the X chromosome, leaving just one functional. For years, the mechanics behind this X chromosome inactivation have been murky, but scientists from theEli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLAhave now taken a major step forward in understanding the process.Their findings, based on research on mouse stem cells, upend previous assumptions about how X inactivation is initiated in female embryos and could lead to new ways to treat some genetic disorders, as well as a better understanding of how genes on other chromosomes are silenced.   “X inactivation is one of the most fundamentally important processes in development, and I think this study is a slam dunk in finally understanding it,” said Kathrin Plath, a professor of biological chemistry and senior author of the paper,published in the journal Cell.Because female cells have two X chromosomes and male cells have only one X and a Y, the inactivation process prevents females from receiving a double dose of X-related proteins. In some female cells, the X inherited from the mother is silenced, while in others, the X from the father is shut off — in a seemingly random fashion.Scientists have known for nearly three decades that an RNA molecule known as Xist is required for X chromosome inactivation early in embryonic development. They ’ve also known that hundred...
Source: UCLA Newsroom: Health Sciences - Category: Universities & Medical Training Source Type: news