ATXN1 and Huntington disease: SCA1 belongs to a group of polyglutamine (polyQ) disorders that also includes SCA2, 3, 6, 7, 17, spinobulbar muscular atrophy, Huntington’s disease (HD), and dentatorubropallidoluysian atrophy (Genis et al., 1995; Gusella and MacDonald, 2000; La Spada and Taylor, 2010).