This focus is driven in part because the death of dopaminergic neurons is primarily responsible for the motor features of PD, but also because the most prominent and distinctive neuropathological findings in PD are the presence of neuronal inclusions, termed Lewy bodies.1,2 The findings that alpha-synuclein (encoded by the gene SNCA) is predominantly expressed in neurons,2,3 is the major component of Lewy bodies,3,4 and mutations in SNCA give rise to autosomal dominant PD,5–8 provide a key link between SNCA function, neurons and disease pathogenesis. The gene discussed is SNCA; the disease is Parkinson disease.