Compound Reverses Down Syndrome-like Learning Deficits in Mice

Researchers have identified a compound capable of bolstering learning and memory in mice with a Down syndrome-like condition.

Down syndrome is a condition caused when a person is born with three copies of chromosome 21, rather than two; on average, individuals with Down syndrome have a cerebellum roughly 60 percent of the normal size.

For the experiment, the scientists genetically engineered mice with extra copies of roughly half of the genes found on human chromosome 21. The result was a number of characteristics found in individuals with Down syndrome, including relatively small cerebellums and difficulty learning.

The scientists then administered a single-dose of a small molecule known as a "sonic hedgehog pathway agonist" on the day of the mice's birth and watched as the animals' cerebellum grew to a normal size over time.

"We were able to completely normalize growth of the cerebellum through adulthood with that single injection," Roger Reeves, a professor in the McKusick-Nathans Institute of Genetic Medicine at the Johns Hopkins University School of Medicine, said in a statement.

The team went on to test the treated mice against untreated genetically engineered mice as well as a third group of control mice. The results showed that the treated mice did just as well as the control group in memory and learning tests.

However, the researchers caution, the molecule has yet to be proven safe in humans, though they say they are currently working to develop similar drugs based on the study's results.

As far as the compound's potential as a drug for humans, Reeves warns that it could have a number of unintended consequences, including deadly ones such as cancer.

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

Still, the researchers believe the study may very well mark a step in the right direction.