MAPT and Alzheimer disease: By 40 years of age, there is a ubiquitous occurrence of plaques and neurofibrillary tangles of hyperphosphorylated tau suggestive of Alzheimer’s disease (AD), as well as clinical signs of dementia, including changes in sociability, language, and depressive symptoms (Teller et al., 1996; Head et al., 2016; Godfrey and Lee, 2018).