PolyQ disorders include the following diseases: Huntington disease, dentatorubural-pallidoluysian atrophy (DRPLA), spinocerebellar ataxia type 1 (SCA1), SCA2, SCA3/Machado-Joseph disease (MJD), SCA6, SCA7, SCA17, and SBMA. Here, ATXN2 is linked to Machado-Joseph disease.