MAPT and Alzheimer disease: Although the etiology of AD is not completely known, some evidence of extracellular β-amyloid (Aβ) deposits (senile plaques) and τ-protein aggregation (hyperphosphorylation of tau protein) are found in the brain of AD patients, in addition to the selective loss of cholinergic neurons, resulting in a deficit of acetylcholine (ACh) in areas with higher mental functions, such as the cortex and hippocampus [1].