MAPT and Alzheimer disease: Although AD is pathologically characterized by the presence of extracellular deposition of plaques comprised of Aβ peptide and neurofibrillary tangles (NFTs) comprised of hyperphosphorylated-tau protein, accumulating evidence suggests that these abnormal protein deposits are unlikely the causative events in AD as Aβ plaque or NFT volume poorly correlate with the severity of dementia.