SNCA and Parkinson disease: Notably, the hallmark of PD is the presence of Lewy bodies (LBs) whose primary structural component is filamentous α-synuclein (α-syn) (Eriksen et al., 2005; Kouli et al., 2018) and the degeneration of dopaminergic neurons in the substantia nigra pars compacta responsible for the motor impairments (Moore et al., 2005).