The role of PP2A in neurodevelopmental disorders has been well described, and abnormal phosphorylation of tau is observed in AD.136 PP2A has been identified as a tau phosphatase137 and is responsible for approximately 71% of the total tau phosphatase activity in the human brain.138 However, patients with AD show lower PP2A activity in both gray and white matter.139. This evidence concerns the gene PTPA and Alzheimer disease.