Moreover, in vitro and in vivo overexpression of wild-type or mutant α-synuclein in neurons results in protein aggregation and toxicity, thus leading to phenotypes resembling PD (Giasson et al., 2002; Kirik et al., 2002; Lo Bianco et al., 2002; Vekrellis et al., 2009). This evidence concerns the gene SNCA and Parkinson disease.