Epigenetic signatures of regional tau pathology and cognition in the aging and pathological brain.

Primary age-related tauopathy (PART) and Alzheimers disease (AD) share hippocampal phospho-tau (p-tau) pathology but differ in {beta}-amyloid burden and degree of p-tau severity and spread. Thus, PART provides a human model to understand the mechanisms of age and amyloid-independent modifiers of p-tau. Given the dynamics of DNA methylation over the lifespan, we (1) performed an epigenome-wide association study of PART that nominated 13 loci associated with p-tau; (2) developed two novel epigenetic clocks predictive of p-tau in age-, and {beta}-amyloid-independent manners: "TauSeverity" relates hippocampal p-tau severity in PART and AD and synaptic transmission genes; "TauSpread" relates to p-tau spread to frontal cortex of AD and neuroinflammatory genes; and (3) a machine learning classifier that identifies low- and high resilience individuals with overlapping neuropathological features but distinct epigenetic, transcriptomic, and clinical features. We conclude that the epigenome contributes to the severity and spread of p-tau pathology, guided by distinct pathways with cognitive consequences.