F2RL3 and Prader-Willi syndrome: Folic acid is expected to exert a global effect on the genome; however, if we can identify genes in which the epigenome is changed in particular disorders (for example, the SNRPN gene in Prader-Willi syndrome during gametogenesis [19,20] and the coagulation factor II (thrombin) receptor-like 3 (F2RL3) gene in heavy smokers [65]), it might be possible to selectively restore the specific epigenomic status of the causative gene region.