OPRM1 and cerebellar ataxia: While cerebellar tissue has a broad expression profile, a neural cell culture model would express only a small subset of these molecules, so further validation experiments were focused on Oprm1, which exhibited an exceptional exon-splicing index of 39.7, and which acts to dampen glutamatergic neurotoxicity in the contacts between cerebellar granule neuron projections (parallel fibres) and Purkinje neuron dendrites [198,199,200], which is the cerebellar site most vulnerable to ataxia pathogenesis [201,202].