MAPT and neurodegenerative disease: There is an open question about the cell biological heterogeneity of tau deposits in human conditions [17] and, in other contexts, heterogeneity has been laid at the door of protein conformation; in neurodegenerative disease caused by misfolding of the cellular prion protein PrPC, ensembles of different conformers have been equated with “clouds” of self-templating protein strains [18].