STUB1 and cerebellar ataxia: Bolstering the evidence that loss-of-function mutations in CHIP are causal to ARCA, a second group using exome sequencing reported STUB1 mutations in six patients with ataxia and cerebellar degeneration from three unrelated families.18 In one family, all affected siblings demonstrated a homozygous mutation in STUB1, whereas the patients in the remaining families demonstrated compound heterozygous mutations (Figure 1a; Table 2), all of which were predicted to substantially affect CHIP protein function.