SNCA and Parkinson disease: Specifically, genetic loss of α-synuclein significantly attenuates the loss of tyrosine hydroxylase-positive DA neurons and PD-like symptoms upon MPTP exposure (Dauer et al., 2002; Schluter et al., 2003), and MPTP treatment reciprocally exacerbates Lewy body pathology in mutant α-synuclein transgenic models (Nieto et al., 2006; Yu et al., 2008).