Rab GTPase dysfunction including impaired RAB geranylgeranylation (i.e., essential post-translational modification that allows Rab proteins to interact with intracellular membranes) is associated with the pathogenesis of neurodegeneration (e.g., Alzheimer's and Parkinson's diseases) and neurogenesis impairment (e.g., ASD) (55–59). The gene discussed is RAB6A; the disease is Parkinson disease.