MAPT and Alzheimer disease: A balanced isoform expression and epigenetic regulation of the isoforms seem to be crucial for both sporadic and genetic TAU-related diseases: Mutations in intronic MAPT regions that lead to an altered isoform expression of TAU, but not the overall protein amount or the amino acid sequence, are sufficient to cause Frontotemporal Dementia with tauopathy (FTD-TAU) reminiscent of AD and Progressive Supranuclear Palsy (PSP) [41,42].