That program seems to go awry in a rare degenerative disease of the nervous system called spinocerebellar ataxia type 1 (SCA1), caused by a mutation similar to the one behind Huntington's disease. (sciencemag.org)
Well, the ataxin - 2 gene can develop an expanded CAG repeat, and when it does, it causes a polyQ disease called spinocerebellar ataxia type 2 (SCA2). (en.hdbuzz.net)
«Fruit flies reveal normal function of gene mutated in spinocerebellar ataxia type 7.» (sciencedaily.com)