MAPT and tauopathy: The prion-like propagation of tauopathies involves the following steps: (1) generation of a seed, a tau unit able to propagate the pathology; (2) secretion of seed-competent tau from a diseased cell; (3) uptake of seed-competent tau by an unaffected cell; and (4) templated misfolding generating new tau seeds in the recipient cell.