Ataxin-2 has many functions such as endocytic receptor cycling, translational regulation, embryonic development, energy metabolism and weight regulation. Mutations of the Ataxin-2 gene cause spinocerebellar ataxia 2 (SCA2), a neurodegenerative disorder leading to predominant loss of Purkinje cells in the cerebellum and impairment of motor coordination. In SCA2, expansion of a CAG repeat in exon 1 of the Ataxin-2 (ATXN2) gene causes expansion of a polyQ domain in the ATXN2 protein.