Down’s Syndrome Cells, science, medical research, Y chromosome,extra chromosome, XIST technique, Phenomena:
But some disorders pose greater challenges. Down’s syndrome, for example, happens when people are born with three copies of the 21st chromosome, rather than the usual two. This condition, called trisomy, leads to hundreds of abnormally active genes rather than just one. You cannot address it by correcting a single gene. You’d need a way of shutting down an entire chromosome.
But half of us do that already. Women are masters of chromosomal silencing.
Even if that worked, it would be very challenging to use the XIST technique in people—you’d need to get the giant gene into the right cells at the right stage. “I doubt that XIST by itself has the potential to become a therapeutic agent in patients,” says Stylianos Antonarakis from the University of Geneva.
Lawrence agrees, but she thinks there might be exceptions. For example, many children with Down’s develop myoproliferative disease, where they produce too many blood cells and run a high risk of leukaemia. If doctors saw kids with this condition, it might be possible to activate XIST in their blood stem cells, to prevent them from developing cancer. “That’s one of the more likely possible uses,” says Lawrence.
The study also has more immediate benefits: “It’s a way of getting at the biology that underlies the different aspects of Down’s,” says Lawrence. The syndrome includes dozens of symptoms across many different organs, including intellectual disabilities, heart problems, leukaemia and Alzheimer’s at an early age. Matching these up to the hundreds of genes on chromosome 21 has been a herculean task. “There are many studies that point to different genes but it’s still a pretty confused field,” says Lawrence.