In a finding that could pave the way for new treatments, scientists say they’ve found an “off switch” that can be applied to the extra chromosome responsible for Down syndrome.

Researchers reported Wednesday that they were able to silence the extra twenty-first chromosome in human stem cells in the laboratory. The finding, published in the journal Nature, offers the first evidence that it may be possible to suppress the genetic defect that causes Down syndrome.

“Our hope is that for individuals living with Down syndrome, this proof of principle opens up multiple exciting new avenues for studying the disorder now, and brings into the realm of consideration research on the concept of ‘chromosome therapy’ in the future,” said the study’s lead author, Jeanne Lawrence, a professor of cell and developmental biology at the University of Massachusetts Medical School.

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More immediately, researchers say the development dramatically enhances the opportunities to learn more about Down syndrome. Compared to other disorders caused by a single gene, studying the impact of an entire extra chromosome has been much more difficult.

For the study, Lawrence and her colleagues looked at a RNA gene called XIST that’s typically responsible for turning off one of the two X chromosomes found in females. They strategically inserted the XIST gene into stem cells that were derived from an individual with Down syndrome. Doing so, effectively silenced the extra chromosome, the researchers said.

“We now have a powerful tool for identifying and studying the cellular pathologies and pathways impacted directly due to over-expression of chromosome 21,” said Lawrence who now plans to use her findings to investigate whether chromosome therapy can be effective in mouse models of Down syndrome.