We biochemically and ultrastructurally investigated abnormal tau proteins in brains with AD and other tauopathies, such as PiD, PSP, CBD, and FTDP-17T (MAPT mutation cases with +13 or +16 intron 10 mutation), and confirmed that the major species of abnormal tau deposited in these brains are all six tau isoforms in AD, only 3R tau isoforms in PiD, and only 4R tau isoforms in PSP, CBD and FTDP-17T (with +13 or +16 intron 10 mutation) [54,61]. Here, MAPT is linked to Alzheimer disease.