RAB3B and Parkinson disease: Our work on Rab function in PD first demonstrated that Rab3B, which is enriched in synaptic vesicles and involved in exocytosis and neurotransmitter release, is intrinsically more highly expressed in A10 dopaminergic neurons, which are less vulnerable to degeneration in PD, than in A9 substantia nigra pars compacta neurons [30, 31].