New Compound Reverses Down Syndrome in Mice: Implications for Future Research

First Posted: Sep 05, 2013 08:04 AM EDT

Scientists have taken another step forward when it comes to treating Down syndrome. They've discovered a compound that dramatically bolsters learning and memory in mice that have had Down syndrome-like symptoms since birth. This "reversal" of the syndrome could help with future research.

Down syndrome is a condition that occurs when people have three, rather than the usual two, copies of chromosome 21. As a result of this, people with Down syndrome have extra copies of the more than 300 genes that are housed on that chromosome. This, in turn, leads to intellectual disabilities, distinctive facial features and sometimes heart problems and other health effects.

The compound is a small molecule known as a sonic hedgehog pathway agonist. Currently, it has not been proven safe to try in people with Down syndrome. Yet this latest discovery does hold promise for developing drugs like it.

"Most people with Down syndrome have a cerebellum that's about 60 percent of the normal size," said Roger Reeves, one of the researchers, in a news release. "We treated the Down syndrome-like mice with a compound we thought might normalize the cerebellum's growth, and it worked beautifully. What we didn't expect were the effects on learning and memory, which are generally controlled by the hippocampus, not the cerebellum."

In the experiment, the researchers used mice that were genetically engineered to have extra copies of about half of the genes found on human chromosome 21. This causes the mice to have many characteristics similar to people with Down syndrome. The scientists injected the compound into the Down syndrome-like mice just once on the day of their birth while their cerebellums were still developing. They then tested the treated mice against untreated Down syndrome-like mice and normal mice.

It turned out that the treated mice performed just as well as normal mice in tests. This is a huge step toward potentially developing drugs for human use. Currently, the researchers plan to conduct more research to find out exactly why the treatment works. Yet the scientists remain cautious.

"Down syndrome is very complex, and nobody thinks there's going to be a silver bullet that normalizes people," said Reeves. "Multiple approaches will be needed."

The findings are published in the journal Science Translational Medicine.

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