MAPT and Alzheimer disease: The pathogenic mechanisms of tau in AD are associated with tau post-translational modifications, especially hyperphosphorylation, and also SUMOylation, nitration, glycation, methylation, prolyl-isomerization, and aggregation, a mixture of 3- and 4-repeat tau isoforms (3R and 4R) in assembled states that contain paired helical filaments (PHFs), straight filaments and oligomers [167] that contribute to neuronal death.