MAPT and Alzheimer disease: Whereas, in human AD brains, there are many sites of tau phosphorylation (including Ser189, 194, 202, 205, 207, 262, 396, 404, and Thr231) that contribute to PHF aggregation leading to NFT formation; tau phosphorylation in the brain of aged dogs with cognitive dysfunction may be limited to particular phosphorylation sites (i.e., Ser189, 207, and 396), so NFTs would not develop [98].