The authors concluded that this CAG expansion might affect PPP2R2B expression, and is probably causative due to the lack of such expansion in controls, and the correlation between expansion degree and disease (Holmes et al., 1999); however, no expression or functional studies were performed to conclusively point out PPP2R2B as the cause of spinocerebellar ataxia 12, or to elucidate the mechanism through which this disease manifests itself. This evidence concerns the gene PPP2R2B and cerebellar ataxia.