Technique could 'switch off' Down's
A way to "switch off" the genetic defect responsible for Down's syndrome has been developed by scientists.
The technique has only been tried on laboratory cell cultures but researchers hope it could pave the way for a new form of "chromosomal therapy".
Children with Down's syndrome are born with three copies of a particular DNA package rather than the usual two.
The extra version of chromosome 21 leads to the characteristic physical appearance associated with Down's, as well as a multitude of health problems and shortened life span.
Correcting Down's with gene therapy has been too great a challenge for scientists even to contemplate. But now researchers in the US have demonstrated a way to silence the whole unwanted chromosome, turning off hundreds of genes at once and removing the root cause of the disorder.
They did it by harnessing a naturally occurring chromosome "off switch", the XIST gene. XIST 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's 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.
The team, whose findings are published in the journal Nature, remain cautious about where the research might lead. But the scientists plan to see if the technique can be used to correct Down's syndrome defects in mice.
Neurogeneticist Dr Lucy Raymond, from Cambridge University, said: "This is an exciting breakthrough, but this process is still at a very early (cellular) stage and we are nowhere near seeing this procedure being used in the treatment of Down's syndrome in people."