To investigate the utility of these cells as a source of hyperphosphorylated tau seeds, we incubated eGFP-0N3R or 0N4R expressing HEK293 cells with sarkosyl-insoluble tau extracted from AD brain or HA-0N3RAD HEK293 cells (HA-0N3RAD seed) (Fig. 4C). Here, MAPT is linked to Alzheimer disease.