Abstract TP227: Identification Of Somatostatin (sst) Interneuron-specific Micrornas And Transcriptome Associated With Cerebral Ischemia

Background: Somatostatin (SST) lineage neurons, the second largest family of GABAergic interneurons in the neocortex, play a critical role in cortical activity and neuroplasticity after stroke. microRNAs (miRNAs) play an important role in mediating ischemic brain repair. Elucidating changes of miRNAs in SST neurons after stroke may provide molecular insight into SST neuron function. Methods: To systematically determine miRNA expression in SST neurons, we employed a miRNA tagging and affinity-purification (miRAP) method to select specific SST neurons via the Cre-loxp binary system in male SST-tAgo2 (tAgo2: a GFP-MYC-Ago2 fusion protein) mice subjected to 7 day middle cerebral artery occlusion (MCAO) (N=3/group). Results: Using miRNA sequencing, we found a total of 523 known and novel miRNAs with distinct profiles that were expressed in SST neurons isolated from ischemic hemispheres compared to miRNAs from sham operated mice. Among them, 70 and 7 miRNAs showed significantly increased and decreased expression, respectively, with a fold change above 2.0 and over 100 copy numbers. Top 3 upregulated miRNAs included miR-381-3p, miR-543-3p and miR-433-3p, while the top 3 downregulated ones were miR-9-5p, miR-423-5p and miR-486b-5p. Furthermore, using miRAP method in combination with RNA-sequencing, we uncovered over 1000 differential gene expression with at least 1.5-fold enrichment in ischemic SST neurons. Integrative analysis of miR-mRNA network by IPA algorithm revealed that 23 miRNAs were predicted to target deregulated mRNAs. Enriched pathways targeted by miRNAs were involved in NTRK3 (neurotrophic receptor tyrosine kinase 3), insulin, PI3K, EGFR1, mTOR signaling, etc, which are associated with neurodevelopment, neuronal growth and survival. These data highlight the importance of these gene regulatory mechanisms to SST neuron function after stroke. Summary/Conclusion: Taken together, our study provides comprehensive miRNA and transcriptional signatures for SST neurons after stroke. These data will facilitate a deeper understanding of the neuroplasticity after brain injury, potentially leading to new therapeutic targets against ischemic stroke. Funding: NIDDK Diacomp 21AU4165 and AHA/ASA 18IPA34170331 (X.S.L).