SNCA and Parkinson disease: Parkinson’s disease (PD) is a neurodegenerative disorder characterized by loss of dopamine (DA)-producing neurons in the substantia nigra pars compacta (SNc), decreased levels of DA primarily in the caudate nucleus and putamen, accumulation of insoluble α-synuclein aggregates (i.e., Lewy bodies and Lewy neurites)1, and a slowly progressive worsening of clinical symptoms.