MAPT and Alzheimer disease: Tauopathies show differing aggregation compositions of tau protein, with principally 4R tau aggregating in PSP, CBD, and frontotemporal dementia with Parkinsonism associated with chromosome 17 (FTDP-17) (Arai et al., 2001, Buee Scherrer et al., 1996); 3R tau proteins aggregating in Pick's disease (Delacourte et al., 1996); and both 3R and 4R tau aggregating in Alzheimer's disease (Sergeant et al., 1997, Williams, 2006).