Decoded: What 'silences' X chromosome in girls

New York, Jan 11: 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 D 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 R” is insufficient to silence the X chromosome. “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 R’ to silence the X-chromosome,” he elaborated.  (IANS)