MAPT and Alzheimer disease: Neuropathologically, AD is characterised by: (1) neuronal loss in specific brain regions – notably the medial temporal lobe structures and the temporo-parietal association cortices (Box 1); (2) intraneuronal neurofibrillary tangles composed of aggregated and often truncated and hyperphosphorylated tau protein (Box 1); and (3) extracellular neuritic plaques, which consist of deposits of β-amyloid (Box 1) peptides, mainly its 42-amino-acid isoform (Blennow et al., 2006) (see poster).