ATXN2 and spinocerebellar ataxia type 2: The study was conducted with the hypothesis that lowering ATXN2 expression might be therapeutic because of a gene dose-phenotype relationship in polyQ diseases: SCA2 patients and mice homozygous for the mutated ATXN2 allele have more severe SCA2 phenotypes vs. heterozygous individuals [5,6], and phenotypes of other polyQ disease models are reversible [7–10].