Pick's disease associated with the novel Tau gene mutation K369I

Exonic and intronic mutations in Tau cause neurodegenerative syndromes char acterized by frontotemporal dementia and filamentous tau protein deposits. We describe a K369I missense mutation in exon 12 of Tau in a patient with a pathology typical of sporadic Pick's disease. The proband presented with s evere personality changes, followed by loss of cognitive function. Detailed postmortem examination of the brain showed atrophy, which was most pronoun ced in the temporal lobes; and numerous tau-immunoreactive Pick bodies and Pick cells in the neocortex and the hippocampal formation, as well as in su bcortical brain regions. Their appearance and staining characteristics were indistinguishable from those of sporadic Pick's disease. However, immunobl ot analysis of sarkosyl-insoluble tau showed three major bands of 60, 64, a nd 68 kDa, consistent with the presence of 3- and 4-repeat tau isoforms, as in Alzheimer's disease. Isolated tau filaments were irregularly twisted ri bbons, with a small number of Alzheimer-type paired helical filaments. In t he presence of heparin, tau proteins with the K369I mutation formed short, slender filaments. Biochemically, recombinant tau proteins with the K369I m utation showed reduced ability to promote microtubule assembly, suggesting that this may be the primary effect of the mutation by providing a pool of aberrant tau for filament assembly. Taken together, results indicate that t he K369I mutation in Tau can cause a dementing disease with a neuropatholog y like that of Pick's disease.