Scientists "Switch Off" Down's Syndrome's Extra Chromosome in a Lab

In human cells in a lab, scientists have discovered a way to "switch off" the chromosome that causes Down's syndrome's symptoms.

Because Down's syndrome occurs when an individuals has three, rather than two, copies of chromosome 21, the study, published in the journal Nature, is seen as a major step in one day being able to treat the disorder.

Led by Dr. Jeanne Lawrence, a cell biologist at the University of Massachusetts Medical School, the team of researchers devised an approach that mimics the natural process that silences one of the two X chromosomes carried by all female mammals called XIST (the X-inactivation gene).

The researchers spliced the gene into one of three copies of chromosome 21 in cells from a person with Down's syndrome and inserted a genetic "switch" that allowed them to turn off XIST by dousing the cells in antibiotic doxycycline, Nature reported.

As they did this, the expression of individual genes along chromosome 21 thought to contribute to Down's syndrome's development problems were dampened.

The experiment used induced pluripotent stem cells, which are capable of developing into many different kinds of cells. For this reason, the researchers believe that they may one day be able to study the effects of Down's syndrome in a variety of organs and tissue types, which in turn could lead to treatments designed to address the multitude of degenerative symptoms those with Down's syndrome tend to develop.

"The idea of shutting off a whole chromosome is extremely interesting" in Down's syndrome research, stem-cell researcher Nissim Benvenisty of Hebrew University in Jerusalem told Nature.

He anticipates future studies, he added, that split altered cells into two batches: one with the extra chromosome 21 turned on, and one with it off. In so doing, researchers could then compare how they function and respond to treatments.

"The research means that we have a new way - right away - to study the cellular basis for Down's syndrome" that could one day lead to drugs designed to treat it, Lawrence told BBC News.

"At the same time, we have made it conceivable - not necessarily possible or effective, that still needs to be proven - but conceivable that you could use just a single gene to correct the over-expression of the whole chromosome."