While levels of tau are elevated in the plasma, CSF, and brain of patients with Alzheimer's disease, no consensus exists that tau is causative of Alzheimer's disease (Mandelkow and Mandelkow, 1998; Gendreau and Hall, 2013; Tarasoff-Conway et al., 2015; Josephs, 2017; Orr et al., 2017; Xin et al., 2018; Naseri et al., 2019; Harrison et al., 2020; Ishida et al., 2022). This evidence concerns the gene MAPT and Alzheimer disease.