Mutations in the gene encoding β-III spectrin (SPTBN2) lead to spinocerebellar ataxia type-5 (SCA5) (11) and spectrin-associated autosomal recessive cerebellar ataxia type-1 (SPARCA1) (12), two human neurodegenerative diseases involving gait ataxia and cerebellar atrophy. Here, SPTBN2 is linked to spinocerebellar ataxia type 5.