MAPT and argyrophilic grain disease: Various forms of aggregated tau have been used as seeds for intracerebral injection in animal models, including pre-formed fibrils (PFFs) derived from in vitro assembly of mutant or WT human or mouse tau, brain extracts from transgenic mutant P301S or P301L human tau overexpressing mice, or pathologic tau purified from brains of patients with AD, CBD, AGD, or PSP.