CLP1 and pontocerebellar hypoplasia: Additionally, mutations in exosome core subunits and in CLP1, which has been implicated in snRNA 3′ end processing (Hallais et al. 2013), have shown to be causal to other subtypes of PCH (Wan et al. 2012; Boczonadi et al. 2014; Schaffer et al. 2014), consistent with the idea that maintaining the balance of enzyme activity at the 3′ end of RNA is crucial to proper neurological function.