MAPT and Alzheimer disease: There exist three main hypotheses for the pathogenesis of the disease: (i) cholinergic hypothesis which maintains that decreased acetylcholine (ACh) contributes to the cognitive decline commonly observed in AD [2]; (ii) amyloid hypothesis which supposes that the accumulation of amyloid-β (Aβ) is the fundamental cause of AD [3]; (iii) tau protein hypothesis which holds that the dysfunction of hyperphosphorylated microtubule-associated protein tau results in neurofibrillary lesions and then initiates AD [4].