miRNA degradation in post-stroke brain

About This Grant

Project Summary/ Abstract An immediate manifestation of stroke is the altered expression of coding and noncoding (ncRNA) genes including microRNAs (miRNAs), which play a crucial role in regulating post-stroke brain damage and recovery. The miRNAs typically suppress target mRNA translation, and their stability is controlled by multiple factors, including biogenesis, degradation, and interactions with other RNAs such as long ncRNAs (lncRNAs). However, the mechanisms driving miRNA degradation after stroke remain poorly understood, limiting their therapeutic potential. Emerging evidence highlights Target-Directed miRNA Degradation (TDMD) as a key pathway regulating miRNA stability. Unlike conventional miRNA activity, where miRNAs suppress target mRNAs, TDMD enables target RNAs to induce miRNA degradation when they exhibit extended complementarity beyond the miRNA seed sequence. However, its role in stroke pathogenesis remains largely unexplored. Understanding whether TDMD contributes to miRNA depletion in the post-stroke brain could open new avenues for targeted gene regulation and therapeutic intervention. Our research highlighted that miRNA miR-7 is significantly downregulated in its mature form following stroke, despite its biogenesis remaining unaffected. This results in the induction of its primary target, α-synuclein (α-Syn), which exacerbates ischemic brain injury. Since the underlying cause of miR-7 degradation remains unclear, we hypothesize that TDMD is a critical mechanism for regulating miRNA levels in the post-stroke brain. Using bioinformatic analysis we noted that brain-enriched lncRNA Cyrano can preferentially bind miR-7 with extended complementarity beyond the seed sequence. Our preliminary studies showed significant induction of Cyrano in the post-stroke brain. Preliminary studies further showed that Cyrano deletion leads to increased miR-7 levels in the ischemic brain, confirming the lncRNA- miRNA relationship and miR-7 degradation likely through TDMD. TDMD requires ZSWIM8, a ubiquitin ligase, to expose miRNA for degradation. Our preliminary studies showed increased ZSWIM8 expression in the post- stroke brain, while siRNA targeting ZSWIM8 reduced ischemic brain injury, providing further evidence of TDMD activation. Building on preliminary evidence, we will therefore investigate TDMD as a key molecular mechanism driving post-transcriptional miRNA degradation in the post-stroke brain. We will pursue two aims to decipher the involvement of TDMD. In Aim 1, we will test that TDMD regulates miRNA miR-7 levels and post-stroke secondary brain damage whereas in Aim 2, we will test that TDMD requires ZSWIM8 for miR-7 depletion in the post-stroke brain. The overall goal is to uncover the prevalence and impact of TDMD in regulating miRNA levels and function after stroke. The long-term goal is to prioritize the development of newer therapies to improve post-stroke functional outcomes and facilitate recovery.