In the case of introduction of AD-tau seeds, CTFs of 20, 22, 30, 36, 40 kDa were detected in insoluble fractions extracted from cells expressing 3R tau, and CTFs of 20, 22, 25, 36, 40 kDa were detected in insoluble fractions extracted from cells expressing 4R tau. Here, MAPT is linked to Alzheimer disease.