There is evidence suggesting that nsDAn surviving the SN degeneration may present a partial loss of their phenotypic characteristics in the PD (Kastner et al., 1993; Miller et al., 1999; Gonzalez-Hernandez et al., 2001, 2004; Chu et al., 2006), a fact that could explain why a portion of the melanin-positive SN neurons does not express TH or other dopaminergic markers in PD (Kordower et al., 2013). This evidence concerns the gene TH and Parkinson disease.