BDNF and Parkinson disease: In the case of PD, the main genes which are epigenetically regulated through methylation are SNCA, PARK6, CYP2E1, PINK1, BDNF, FGF, MAPT, MTHFR, OLFR 151, PARK16, PARK2, PARK7, TPPP, PDE4D, and METRNL.