MAPT and Alzheimer disease: The neuropathological hallmarks of AD are intracellular neurofibrillary tangles (NFTs) composed of paired helical filaments (PHFs) and straight filaments (SFs) mainly constituted of hyperphosphorylated tau protein, a microtubule associated protein (MAP), neuropil threads (NTs), dystrophic neurites, and extracellular deposits of β-amyloid (Aβ) as the major component of senile plaques (SPs) in the brain.