MAPT and Alzheimer disease: AD is characterized clinically by progressive deterioration of memory, and pathologically by histopathological changes including extracellular deposits of amyloid-β (Aβ) peptides forming senile plaques (SP) and the intracellular neurofibrillary tangles (NFT) of hyperphosphorylated tau in the brain, which are commonly regarded as the hallmarks of the disease.