MAPT and early-onset autosomal dominant Alzheimer disease: Several preclinical investigations have demonstrated that activated microglia trigger tau phosphorylation in animal models of Alzheimer's disease and other tauopathies.22,39-41 Another study on brain tissue samples of Alzheimer's disease patients and mice demonstrated that microglia effectively phagocytose hyperphosphorylated tau seeds, yet are not fully able to neutralize the tau seeding activity.42 Instead, microglia release the pathological tau seeds into the extracellular space, leading to a potential cascade of subsequent tau hyperphosphorylation, misfolding and dissemination.