MAPT and Alzheimer disease: Biochemical analysis using anti-tau antibodies for phosphorylated Ser 202 (CP13) and Ser 202/Thr205 (AT8) present in early (pre-tangles) and advanced NFTs, and Ser 396/404 (PHF-1), a marker of late NFT stages in AD brain (Table 1), revealed enhanced tau phosphorylation in the cortex and hippocampus of PS cKO mice (Fig. 2a, b).