MAPT and Alzheimer disease: From a histological point of view, AD is mainly characterized by three pathological hallmarks including neuronal loss, extracellular amyloid plaques consisting of aggregated amyloid-β (Aβ) peptides, as well as the intracellular formation of neurofibrillary tangles composed of a hyperphosphorylated form of the microtubule-associated protein tau [2,3,4,5].