The discovery of the involvement of MAPT mutations in FTD associated with parkinsonism (FTDP; Hutton et al., 1998; Poorkaj et al., 1998; Spillantini et al., 1998) and several other pathologies (Goedert and Spillantini, 2019), together with the modest success of clinical trials focused on amyloid beta (Aβ) pathology in AD, highlighted the importance of studying tau as a potential target for the treatment of neurodegenerative diseases associated with dementia. This evidence concerns the gene MAPT and Alzheimer disease.