Down syndrome research welcomed

Down Syndrome Ireland has given a cautious welcome to news that scientists in the US have been able to switch off or "silence" the extra chromosome responsible for Down syndrome in laboratory cell cultures.

“We welcome this research but think we’re still a long way from having a viable therapy,” chief executive of Down Syndrome Ireland Pat Clarke said.

“It is one thing to say something is possible, but it will be a long, long time before there will be any kind of realistic and viable therapy or method of delivering it; you’re certainly talking many, many years,” he added.

Mr Clarke was commenting on a study by US researchers who say they have demonstrated a way to silence the extra chromosome responsible for Down syndrome. The findings were published in the science journal Nature.

The technique has only been tried on laboratory cell cultures but researchers hope it could pave the way for a new form of “chromosome therapy”.

Children with Down syndrome are born with three copies of chromosome 21 rather than the usual two. The researchers have demonstrated a way to silence the extra chromosome, turning off hundreds of genes at once.

'Off switch'

They did so by harnessing a naturally occurring chromosome “off switch”, the XIST gene, which normally has the job of silencing one of the two X chromosomes in female cells. In this way, X chromosome activity in women matches that of men, who only have one X chromosome.

The scientists first created "induced" stem cells from skin cells donated by Down syndrome patients, each of which contained three copies of chromosome 21 in its nucleus. By inserting the XIST gene into a specific location in one copy of chromosome 21, they were able to deactivate it. Gene activity from chromosome 21 then returned to normal.
Additional reporting: PA