Work in 1980s and early 1990s established that the microtubule-associated protein tau is the major component of the paired helical filament of Alzheimer's disease. Similar filamentous deposits are also present in a number of other diseases, including progressive supranuclear palsy, corticobasal degeneration and Pick's disease. In 1998, the relevance of tau dysfunction for the neurodegenerative process became clear, when mutations in the tau gene were found to cause the inherited "frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17)". The paper highlighted here [Spillantini M.G., Murrell J.R., Goedert M., Farlow M., Klug A. and Ghetti B. (1998) Mutation in the tau gene in familial multiple system tauopathy with presenile dementia. Proc. Natl. Acad. Sci. USA 95, 7737-7741] reported a mutation at position + 3 in the intron following alternatively spliced exon 10 of the tau gene in a family.