MAPT and Alzheimer disease: To validate the seeded tau aggregation assay, we treated HEK-293FT cells expressing HA-tau151-391 with various amounts from 0.375 to 1.5 A.U. of AD O-tau for 42 h and analyzed RIPA-insoluble and -soluble taus by immuno-dot blots developed with anti-HA (Figure 5B).