Historically, loss of Calb-immunoreactive (Calb+) Purkinje cells has been widely used as a surrogate for Purkinje cell degeneration in SCA mouse models, including models of SCA1 [24], SCA2 [43], SCA3 [44], and SCA17 [45]. Here, ATXN3 is linked to autosomal dominant cerebellar ataxia.