MAPT and Alzheimer disease: At the neuropathological level, AD is defined by extracellular Aβ plaques, formed as a result of the misprocessing of amyloid precursor protein (APP) as well as aggregation of hyperphosphorylated tau proteins into neurofibrillary tangles (NFTs; Buée et al., 2010; Querfurth and LaFerla, 2010; Masters et al., 2015).