Studies on human postmortem tissues indicated that the phosphorylation level of tau isolated from autopsied AD brain is 3- to 4-fold higher than that of non-AD brains.50 To date, more than 45 phosphorylation sites have been identified in tau protein isolated from AD brains.51 However, no pathologic tau aggregation including NFTs have been reported in any previously published App transgenic or knock-in mouse models.9 Similar to humans, rats contain 6 isoforms of tau (3 × 4R, 3 × 3R), although the ratio of 4R/3R tau isoforms is different (9:1 in rats; 1:1 in humans). This evidence concerns the gene MAPT and Alzheimer disease.