US researchers experimented on the Ts65Dn mouse which “recapitulates some major brain structural and behavioral phenotypes of [Down’s syndrome]”. They found that “a single treatment of newborn mice with the Sonic hedgehog pathway agonist SAG 1.1 (SAG) result[ed] in normal cerebellar morphology in adults.” [Science, volume 5, issue 201] If such postnatal therapy could be administered in humans, it would avoid the ethical problems of germline genetic manipulation.