MAPT and Alzheimer disease: AD is the most frequent age-associated neurodegenerative disorder characterized by aberrant processing of the amyloid precursor protein (APP), increasing Aβ1-42 peptide accumulation, and formation of intraneuronal neurofibrillary tangles by the hyperphosphorylation of the microtubule-associated protein tau (MAPT) in the brain [47,48,49,50,51].