MAPT and Alzheimer disease: Alzheimer’s disease (AD) is a neurodegenerative disease characterised by three key neuropathological hallmarks: (1) the presence of amyloid beta (Aβ) plaques in the brain parenchyma, and commonly also within cerebral blood vessels (cerebral amyloid angiopathy); (2) intraneuronal neurofibrillary tangles (NFTs), composed of hyperphosphorylated tau; and (3) neurodegeneration (Stelzmann et al., 1995; DeKosky, 2001; Winner et al., 2011).