HCN2 and Parkinson disease: In terms of hypomethylation, exposure to rotenone, a naturally occurring hetero-pentacyclic pesticide, was shown to drive hypomethylation of HCN2, responsible for regulating neuronal plasticity, and NEFM, driving axonal growth and transport, in kidney cell cultures associated with PD [61], and global hypomethylation in liver cells [42].