PHF1 and Alzheimer disease: We next expressed phosphorylation-mimicking (E) and phosphorylation-abrogating (A) mutant forms of three tau epitopes that are known to be hyperphosphorylated in AD, AT180 (pThr231/pSer235), 12E8 (pSer262/pSer356) and PHF1 (pSer396/pSer404).