GABRB3 and ethylmalonic encephalopathy: The majority of clearly causative mutations were in genes already known to cause EE, including SCN1A, STXBP1, and CDKL5, but two new disease genes emerged: GABRB3 and ALG13. GABRB3 encodes the β3 subunit of the GABAA receptor, supporting the channelopathy hypothesis, while ALG13 encodes a subunit of the uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) transferase that is involved in N-linked glycosylation, an essential modification for protein folding and stability.