MAPT and Alzheimer disease: Cerebrospinal fluid (CSF) amyloid β42 (Aβ42), total tau (T-tau), and phosphorylated tau (P-tau) concentrations are established diagnostic and/or prognostic biomarkers for AD, reflecting the core pathological hallmarks of AD, amyloid plaques, neurodegeneration and the hyperphosphorylation of tau, respectively [1].