It was possible – in the laboratory – to block the activity of the extra chromosome that causes Down syndrome with a single gene, Nature says.
The normal number of chromosomes a human is born with in a cell is 23 pairs, or 46 in total (2 of these chromosomes are sex chromosomes). People with Down’s syndrome have 47 chromosomes, because chromosome 21 is not in two but three copies.
The extra chromosome causes Down syndrome symptoms such as the characteristic appearance, mild to moderate intellectual disability, cardiovascular and digestive problems, and the early development of Alzheimer’s syndrome.
Scientists from the team of Dr. Jeanne Lawrence (University of Massachusetts Medical School) managed to block the excess chromosome using the XIST gene, introduced into laboratory-grown stem cells taken from a person with Down syndrome.
The XIST gene plays an important role in normal cell development in female embryos – it blocks the action of one of the two X chromosomes.
The authors of the research emphasize that the way to the practical use of this type of methods in the treatment of people with Down syndrome is still long (we are talking about decades), but until recently the very idea of blocking the entire chromosome with gene therapy methods seemed unrealistic. So far, scientists have had a hard time (or even failed) to block a single defective gene (PAP)