Loss-of-function mutations in RAB39B are associated with typical early-onset Parkinson disease

Rab proteins are small molecular weight guanosine triphosphatases involved in the regulation of vesicular trafficking.1 Three of 4 X-linked RAB genes are specific to the brain, including RAB39B . Recently, Wilson et al.2 reported that mutations in RAB39B cause X-linked intellectual disability (ID) and pathologically confirmed Parkinson disease (PD). They identified a ∼45-kb deletion resulting in the complete loss of RAB39B in an Australian kindred and a missense mutation in a large Wisconsin kindred. Here, we report an additional affected man with typical PD and mild mental retardation harboring a new truncating mutation in RAB39B . Acknowledgment: The authors are grateful to the patients and their families. They thank Merle Ruberg for critical reading of the manuscript and the DNA and Cell Bank of ICM for sample preparation.