MAPT and Alzheimer disease: In addition, although the accumulation ratio of insoluble 3R tau and 4R tau induced by AD-tau seeds was almost the same in the presence of both 3R tau and 4R tau (Fig. 4A and Supplementary Fig. 8B), AD-tau seeds exhibited higher seeding activity in the presence of only 3R tau substrate than in the presence of only 4R tau substrate.