The most significant outcome of the present study is the discovery that CatD-KO mice develop widespread, robust tauopathy by just ∼ 3 weeks of age, as evident from several independent measures, including Gallyas silver staining resembling NFTs in AD brain, phospho-tau immunoreactivity using multiple well-characterized antibodies, and western blotting for sarkosyl-insoluble phospho-tau. Here, MAPT is linked to Alzheimer disease.