MAPT and Alzheimer disease: PP2A accounts for ~71% of total tau phosphatase activity in the human brain (Liu et al., 2005); and its expression and/or activity have been found significantly decreased under the conditions of AD pathology (see Lambrecht et al., 2013; Taleski and Sontag, 2018 for further references), which should promote hyperphosphorylation of Tau by disturbing the balance between Tau kinase and phosphatase activities mentioned above.