Whereas both the GluD1 and GluD2 proteins are expressed in a variety of brain regions including the cerebral cortex, hippocampus, and cerebellum, GluD2 expression is highest in the cerebellum and present at higher levels than GluD1 [1], potentially explaining the occurrence of ataxia and cerebellar atrophy in patients with GRID2 variants. The gene discussed is GRID2; the disease is Ataxia.