Mutations in the small GTPase gene RAB39B are responsible for X-linked mental retardation associated with autism, epilepsy, and macrocephaly

A study reports that mutations in the small GTPase gene RAB39B are responsible for X-linked Human Mental Retardation (HMR) associated with autism, epilepsy, and macrocephaly. Analyses demonstrate that RAB39B, a novel GTPase of the RAB family, is a neuronal-specific protein required for synapse formation and maintenance, and its downregulation due to mutations impairs the development of neurons and human intellectual abilities.