An early proinflammatory transcriptional response to tau pathology is age-specific and foreshadows reduced tau burden

Age is one of the strongest risk factors for the development of neurodegenerative diseases, the majority of which involve misfolded protein aggregates in the brain. These protein aggregates are thought to drive pathology and are attractive targets for the development of new therapies. However, it is unclear how age influences the onset of pathology and the accompanying molecular response. To address this knowledge gap, we used a model of seeded tau pathology to profile the transcriptomic changes in 3 and 12 month old mice in response to developing tau hyperphosphorylation and aggregation. First, we found the burden of hyperphosphorylated tau pathology in mice injected at 12 months of age was moderately reduced compared to animals injected at 3 months. On a molecular level, we found an inflammation-related subset of genes, including C3 and the disease-associated microglia genes Ctsd, Cst7, and Clec7a, were more expressed early in disease in 12 but not 3 month old mice. These findings provide evidence of an early, age-specific response to tau pathology, which could serve as a marker for the severity of downstream pathology.