10x single-cell RNA sequencing of microglia from wild-type C57BL/6 and P301S mice

The existence and contribution of microglia with senescent-like alterations in the pathogenesis of age-related neurodegenerative disease have been suggested in recent years. However, the identification of this distinct microglial population in vivo has proven challenging, largely due to overlaps in the inflammatory phenotype of activated and senescent microglia. Furthermore, attempts at recapitulating senescence in microglia in vitro are limited. To overcome these challenges, we analyzed the RNA expression patterns of individual microglia from normal mice and the pathogenic tau P301S PS19 mouse model. We have previously demonstrated that p16-expressing senescent microglia occur in these mice when neurodegeneration has occurred. Here we identify a subset of disease-associated microglia with senescent features, notably characterized by the expression of Ccl4. This signature overlaps with established markers of senescence from other cell types. Our characterization of senescent microglia can be used to better understand the role of senescent microglia in various age-related contexts, including whether clearance of senescent microglia represents a viable therapeutic option. P301S and C57BL/6 mice of 9.5 months of age were perfused and cortices and hippocampi isolated. Cortices and hippocampi were incubated with accutase for single-cell dissociation, before myelin removal and CD11b selection.