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Investigators genotyped exome regions in three consanguineous families of patients who had autism, seizures (or electroencephalographic abnormality), and intellectual impairment.
Affected people had various mutations in the branched chain ketoacid dehydrogenase gene (BCKDH). This gene encodes a protein that catabolizes branched chain amino acids (BCAAs; leucine, isoleucine, and valine). Mice with this gene knocked out had low BCAA levels in plasma and in the brain and exhibited neurological impairments that are observed in other autism models — including seizures, tremors, and hind-limb grasping. The knockout mice also showed perturbations in BCAA transporters (which also transport major neurotransmitters) across the blood–brain barrier, as …