Down Syndrome 'Reversed' in Mice Researchers were able to affect the growth of the cerebellum By Arden Dier, Newser Staff Posted Sep 5, 2013 11:03 AM CDT 22 comments Comments A Tuesday, Jan. 24, 2006 file photo shows a laboratory mouse at the Jackson Laboratory. (AP Photo/Robert F. Bukaty, File) (Newser) – We'll start by tempering expectations: The breakthrough you're about to read about has "no direct link" to a human treatment, reports AFP, but it's noteworthy nonetheless. Scientists say they've identified a molecule that "reverses" the effects of Down syndrome in mice. The molecule is called sonic hedgehog pathway agonist, and it was administered to mice who were genetically altered to have characteristics akin to those of Down syndrome. The molecule, which is not approved as safe for humans, spurs a gene to make a protein tied to development. "Most people with Down syndrome have a cerebellum that's about 60% of the normal size," says one of the Johns Hopkins researchers. Science World Report notes that the mice were injected on the day they were born, at which point their cerebellums hadn't fully developed. The single injection appeared to normalize the cerebellum's growth. In an added surprise, memory and learning, "which are generally controlled by the hippocampus, not the cerebellum," were also positively affected. But the researcher explains that applying the treatment to humans is a tricky proposition, and could have unintended consequences, like raising cancer risk.