Abstract WMP116: Ifi27l2a Is A Novel Regulator Of Neuroinflammation And Neurodegeneration In The Post-stroke Brain.

Microglial cells (MG) serve as resident immune cells in the brain and play a critical role in the acute response and chronic recovery to stroke. We compared the MG transcriptomic response to stroke in young and aged mice by single-cell RNA sequencing (scRNAseq) and identified Ifi27l2a (a member of the interferon signaling family) as one of the most highly upregulated genes in MG following ischemic stroke. However, the functional role of Ifi27l2a in ischemic stroke is not known. Methods: Single cell suspensions were obtained from the brains subjected to permanent distal middle cerebral artery occlusion (pdMCAO) in young and aged mice of both sexes (3 & 20 months). scRNAseq was performed to explore the transcriptional signature in brains at 14-days post-stroke. qRT-PCR and RNAscope were used to validate our scRNAseq findings for Ifi27l2a expression and compare regional transcriptional changes. To determine the role of Ifi27l2a, we used WT and Ifi27l2a +/- (Het) mice. Infarction was measured at 3-day post stroke by TTC staining. Thalamic gliosis were detected by IBA1 and GFAP staining at 2 week post-stroke. Results: Using unbiased scRNAseq analysis, we identified Ifi27l2a as the most highly up-regulated gene in aged MG following stroke. Further analysis showed a positive correlation between Ifi27l2a and multiple “MG activation” genes and senescence-related genes. Our qRT-PCR results validated the scRNAseq findings and further showed that Ifi27l2a was significantly up regulated in thalamus of aged brains (p = 0.04) and trending in cortex (p=0.23, n=4-6) as well as other proinflammatory genes. Using knockout mice, we found that the thalamic gliosis was significantly reduced in the brains of Het, compared to WT (n=6, p<0.05). Primary cortical infarction also was reduced in Het brains compared to WT (n=4-5, p<0.05), suggesting the critical role of Ifi27l2 in evolving brain injury. Conclusions: We identified Ifi272la as a highly up-regulated gene in MG following stroke and demonstrated that Ifi27l2a partial deletion results in reduced brain injury acutely and chronically. Our findings suggest that Ifi27l2a is a novel mediator of neuroinflammation and neurodegeneration, and thus provide the basis for a new therapeutic target to reduce brain injury in aging and stroke.