ITPR1 and spinocerebellar ataxia type 15/16: Spinocerebellar ataxia 15 (SCA15) and Spinocerebellar ataxia 16 (SCA16) are two forms of autosomal dominant pure cerebellar ataxia that involve enormous heterozygous deletions or missense mutations in IP3R1 [15-17] (see Figure 1b and Table 1).