MAPT and Alzheimer disease: While tau I297-E391 peptides have been reported to form PHFs in vitro, tau I297-L441 peptides containing pseudo-phosphorylation at S396, S400, T403 and S404 form only protofilaments presenting the Alzheimer’s disease fold under the same in vitro conditions.46,47 These results support the idea that truncation of N- and C-terminal tau is involved not only in Alzheimer’s disease fold formation but also in PHF formation.