Mouse models have demonstrated that intracerebral injection of either synthetic tau preformed fibrils (PFFs) or human AD-brain-derived pathological tau (AD-tau) can instigate tau pathology in regions of the brain distant from the injection site in either transgenic (Tg) mice expressing mutant human tau or non-transgenic wildtype (WT) mice [20–24]. The gene discussed is MAPT; the disease is Alzheimer disease.