Moreover, polymorphisms within the locus encoding α-synuclein have been found to be associated with the increased risk of PD development (Kay et al., 2008, Mizuta et al., 2008, Pankratz et al., 2009, Scholz et al., 2009, Sutherland et al., 2009), with recent studies suggesting that disease progression to the symptomatic stage correlates with the spreading of pathologic α-synuclein aggregates to dopaminergic neurons of the substantia nigra pars compacta (SNpc) (Braak et al., 2006, Desplats et al., 2009, Luk et al., 2012, Recasens et al., 2014). This evidence concerns the gene SNCA and Parkinson disease.