ATXN1 and Ataxia: Importantly, while mice expressing ATXN1[30Q]-D776 in Purkinje cells manifested severe ataxia from an early age, i.e. as severe as mice with Purkinje cell expression of ATXN1[82Q], disease in ATXN1[30Q]-D776 mice was not progressive leading to Purkinje cell degeneration, i.e. atrophy of the molecular layer, as was observed in ATXN1[82Q] mice (Fig. 1A and B and [13]).