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Wednesday, July 17, 2013

New Genetic Therapy Could Erase Down Syndrome

Erin Witkowski, of Port Jervis, N.Y., and her 16-month-old son Grady pose for photos in New York's Central Park, June 6, 2011. (Richard Drew/AP)

Erin Witkowski, of Port Jervis, N.Y., and her 16-month-old son Grady pose for photos in New York’s Central Park, June 6, 2011. (Richard Drew/AP)

Down syndrome affects nearly six million people worldwide. The genetic disorder impairs physical growth and intelligence, and it can cause serious medical problems, from heart defects to early dementia.

Down syndrome is caused by a chromosome defect and today, the journal Nature reports that researchers may have found a way to correct that defect, though it will be years before it could be used as a therapy in humans.

It’s an application of the idea behind gene therapy. The premise is that if you have a disease that’s caused by a defect in a single gene, a virus engineered to carry a “fix-it” gene can be sent in to remove and replace the abnormal gene.

The new application of this idea is called chromosome therapy.

Down syndrome is caused by the presence of a third copy of chromosome number 21. Chromosome therapy could be used to “silence” or turn off the extra copy, which contains hundreds of genes, with the hope that that would turn off the effects of Down Syndrome.

Guest

Transcript

ROBIN YOUNG, HOST:

It's HERE AND NOW. And today, the journal Nature is reporting that researchers may, may have found a way to turn off the genetic effect that causes Down syndrome even after people are born with it. Down syndrome affects nearly six million people worldwide. It's a genetic disorder that impairs physical growth and intelligence and can cause serious medical problems, from heart defects to early dementia.

This new technique is being called chromosome therapy. It'll be years before it's even used in humans, but even its initial promise is sure to raise questions. And Carey Goldberg, the health reporter at her home station, WBUR, is here to try to answer some. Carey, we know chromosomes are in cells, they hold our genes, we've heard about gene therapy, so what's chromosome therapy and why is that important for people with Down?

CAREY GOLDBERG, BYLINE: Well, gene therapy, that's the still somewhat futuristic idea that if you have a disease that's caused by a defect in a single gene, then we can send in a virus engineered to carry a sort of fix-it gene to cure you. Well, this is an even bolder concept. Chromosome therapy would aim to fix a whole chromosome, which is hundreds of genes, and that's the problem in Down syndrome is that it involves a whole extra copy of chromosome number 21.

YOUNG: So how would you fix that extra copy of chromosome number 21?

GOLDBERG: Well, that's the cracks of the papers that's just out today in the journal Nature. Researchers at the University of the Massachusetts Medical School found a way to silence the extra chromosome. Meaning that it's still there, but its genes don't get turned on. They don't function and cause problems. Here's Jeanne Lawrence, the lead researcher.

DR. JEANNE LAWRENCE: The first time that a single gene has been used to silence a chromosome for the purposes of therapy in a chromosomal abnormality.

GOLDBERG: So possibly in the future, you could use this technique to silence other chromosome problems besides Down syndrome.

YOUNG: Just briefly tell us, what - how would you do that?

GOLDBERG: Well, what they did in this paper was they found a way to reuse something that already occurs in us naturally, which is a gene called XIST. That's X-I-S-T. And in female mammals like me, it already functions to kind of ratchet down one of our X chromosomes. So Dr. Lawrence and her team got what's called a high-risk, high-impact, which means a long shot grant, to try to use this gene that normally affects the X chromosome in order to silence the gene that's a problem in Down syndrome, which is chromosome 21, and it seems to have worked.

YOUNG: OK. But this was just cells in a lab, so, I mean...

GOLDBERG: Right.

YOUNG: ...a lot of questions here. Very early stages, what does it mean for people who already have Down syndrome, and what does it mean for parents who - expecting parents who might have prenatal testing?

GOLDBERG: Right. It's very early work, first of all. Jeanne Lawrence says that in the short term, this ability to silence that extra chromosome could be a really important scientific tool to figure out what goes wrong, and that could lead to drugs that could treat it. And then eventually, it could lead to methods to just turn off that extra chromosome in people who have Down syndrome. But on the prenatal front, I spoke with Dr. Brian Skotko, the co-director of the Down syndrome program at Massachusetts General Hospital, he says that expected parents often ask him whether there's a cure for Down syndrome, and now his answer is going to change.

DR. BRIAN SKOTKO: I can now insert into my conversation research is being done and that there is promise that one day they might be able to figure out how to turn off most of the effects of that extra chromosome.

GOLDBERG: So in other words, these incredibly difficult prenatal Down syndrome decisions might get even harder now, but at least this is a clear advance for Down syndrome.

YOUNG: Wow. Decisions prenatally, but also if someone already has Down syndrome, potentially in the future or something. Carey Goldberg, health reporter at WBUR, thank you so much.

GOLDBERG: You're welcome, Robin. Transcript provided by NPR, Copyright NPR.


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