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Written By: Agencies | Published : January 11, 2016 5:15 PM IST
Nearly every girl and woman on Earth carries two X chromosomes in each of her cells -- but one of them does (mostly) nothing. Do you know why?
That is because it has been silenced, keeping most of its DNA locked up and unread like a book in a cage, scientists led by an Indian-American researcher from the University of Michigan Medical School have revealed. A wide range of relatively rare diseases - as well as relatively common conditions such as autism, haemophilia and muscular dystrophy - are linked to problems with genes found on the X chromosome. The findings could help lead to new ways of fighting diseases linked to X chromosomes in girls and women -- the kind that occur when the X chromosome that does get read has misprints and defects. The team found that a known molecule called Xist RNA is insufficient to silence the X chromosome. (Read: Lack of Y chromosome increases cancer risk in men)
Xist is widely believed to be both necessary and sufficient for X silencing, said team leader Sundeep Kalantry. We, for the first time, show that it is not sufficient and there have to be other factors - on the X-chromosome itself that activate 'Xist' and then cooperate with 'Xist RNA' to silence the X-chromosome, he elaborated. In the future, it may be possible to change the level of these other factors in cells and turn on the healthy, silenced copy of a gene that lies on the inactive X-chromosome, Kalantry added. Although most genes on the inactive X chromosome are fully silenced, a handful of the genes on the inactive X are, in fact, active. It is this set of X-inactivation escapees that the research team was focused on. (Read: X chromosome plays a role in sperm production)
Since the escapee genes are expressed from both the active and the inactive X-chromosomes in females, they produce more gene product in female cells than in male cells which only have a single X. According to Kalantry, it is this higher dose in females that triggers X-inactivation selectively in females; the lower dose in males is insufficient. That means that if researchers can determine exactly which factors cause X-inactivation to occur, they could find ways to affect the activity of genes on the X chromosomes - specifically, genes involved in certain diseases. the authors noted. Many of them have an impact on an individual's thinking and memory capacity, and other aspects of cognition and intelligence. (Read: World hemophilia day 5 interesting facts you didnt know)
In females, we could envision 'reawakening' a healthy copy of an X-linked gene on the inactive X chromosome, by modulating the dose of these so-called escapee genes and ameliorating the effects of the unhealthy copy, Kalantry explained. Unfortunately, this approach probably won't help males with X-linked diseases, because they only have a single X chromosome in each cell and inactivating it would be harmful. The new paper appeared in the journal Proceedings of the National Academy of Sciences.
Source: IANS
Photo source: Getty images
