USP19 and cerebellar ataxia: USP19, found in a proband with epileptic encephalopathy, DD, and hypotonia, encodes ubiquitin-specific protease 19, which is involved in the regulation of ataxin 3 (spinocerebellar ataxia, MIM 109150) and interacts with DOCK7 (epileptic encephalopathy, MIM 615859) and USP7 (autism spectrum disorder) (Additional file 2: Figure S2) [67–69].