Despite a growing clinical literature demonstrating that TBI is an important environmental risk factor for neurodegenerative disease such as CTE7–10 and AD11–14, the causal link and underlying mechanisms between TBI and these neurodegenerative outcomes remains unclear8–10 and the role of tau pathology, a common feature of these neurodegenerative outcomes, is not known7–10, 19. Here, MAPT is linked to neurodegenerative disease.