Researchers Able to Turn Off the Genes That Cause Down's Syndrome

 Genetics  

Researchers working with induced pluripotent stem cells have found a way to block the extra chromosome responsible for Down syndrome—the work may eventually lead to chromosome-level gene therapy to treat Down's and other conditions.

According to a study published in Nature, he insertion of one gene can muzzle the extra copy of chromosome 21 that causes Down’s syndrome,. The method could help researchers to identify the cellular pathways behind the disorder's symptoms, and to design targeted treatments.

“It’s a strategy that can be applied in multiple ways, and I think can be useful right now,” says Jeanne Lawrence, a cell biologist at the University of Massachusetts Medical School in Worcester, and the lead author of the study.

“Genetic correction of hundreds of genes across an entire extra chromosome has remained outside the realm of possibility,” said Lawrence in a release. “Our hope is that for individuals 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.”

Image Source: Jeanne Lawrence Lab

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Lawrence and her team came up with an approach to mimic the natural process that silences one of the two X chromosomes carried by all female mammals. Both chromosomes contain a gene called XIST(the X-inactivation gene), which, when activated, produces an RNA molecule that coats the surface of a chromosome like a blanket, blocking other genes from being expressed. In female mammals, one copy of the XIST gene is activated — silencing the X chromosome on which it resides.

Lawrence’s team spliced the XIST gene into one of the three copies of chromosome 21 in cells from a person with Down’s syndrome. The team also inserted a genetic 'switch' that allowed them to turn on XIST by dosing the cells with the antibiotic doxycycline. Doing so dampened expression of individual genes along chromosome 21 that are thought to contribute to the pervasive developmental problems that comprise Down's syndrome.

The experiment used induced pluripotent stem cells (iPS), which can develop into many different types of mature cells, so the researchers hope that one day they will be able to study the effects of Down’s syndrome in different organs and tissue types. That work could lead to treatments that address degenerative symptoms of Down’s syndrome, such as the tendency of people with the disorder to develop early dementia.

The approach could yield fresh treatments for Down's syndrome — and prove useful for studying other chromosome disorders such as Patau syndrome, a developmental disorder caused by a third copy of chromosome 13.

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SOURCE  Nature

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