While for rare (genetic) tauopathies epigenetic studies are largely missing (but see chapter PSP for MAPT promoter hypomethylation), for the mainly sporadic AD and PD, epigenetic factors are certainly involved, and may play a disease-modifying role also in other (genetic) tauopathies, e.g. modifying the age of onset or severity of symptoms, and also be consequence of gene mutation (as e.g. discussed here for myotonic dystrophy, which changes splicing in a wide-spread fashion, see below). The gene discussed is MAPT; the disease is tauopathy.