The sarkosyl-insoluble fractions derived from Alzheimer’s disease, PiD, PSP, CBD and Huntington’s disease patients’ brains were introduced into SH-SY5Y cells transiently expressing HA-tagged human full-length 3R tau (3R-FL) and 4R tau (4R-FL) without pathogenic mutations. Here, MAPT is linked to juvenile Huntington disease.