MAPT and Alzheimer disease: (1) Blood‐derived hAβ could enter the brains of wild‐type mice and accumulate, forming cerebral amyloid angiopathy (CAA) and Aβ plaques. (2) It induced AD‐related pathological changes in the brains of wild‐type mice, such as hyperphosphorylation of tau protein, neurodegeneration, neuroinflammation, and microhemorrhage. (3) It significantly impaired long‐term potentiation (LTP) in the CA1 region of the hippocampus of wild‐type mice.