TauRD-Y is soluble and diffusely distributed in TauRD-Y cells, but the extracellular addition of Tau aggregates isolated from tauopathy brain tissue or generated in vitro induces its aggregation via template-based seeding, leading to the formation of aggregates that are stably propagated for weeks39,40 (Fig. 1b). Here, MAPT is linked to tauopathy.