Transient Focal Ischemia Significantly Alters the m⁶A Epitranscriptomic Tagging of RNAs in the Brain

Background and Purpose- Adenosine in many types of RNAs can be converted to m⁶A (N⁶-methyladenosine) which is a highly dynamic epitranscriptomic modification that regulates RNA metabolism and function. Of all organs, the brain shows the highest abundance of m⁶A methylation of RNAs. As recent studies showed that m⁶A modification promotes cell survival after adverse conditions, we currently evaluated the effect of stroke on cerebral m⁶A methylation in mRNAs and lncRNAs. Methods- Adult C57BL/6J mice were subjected to transient middle cerebral artery occlusion. In the peri-infarct cortex, m⁶A levels were measured by dot blot analysis, and transcriptome-wide m⁶A changes were profiled using immunoprecipitated methylated RNAs with microarrays (44 122 mRNAs and 12 496 lncRNAs). Gene ontology analysis was conducted to understand the functional implications of m⁶A changes after stroke. Expression of m⁶A writers, readers, and erasers was also estimated in the ischemic brain. Results- Global m⁶A levels increased significantly at 12 hours and 24 hours of reperfusion compared with sham. While 139 transcripts (122 mRNAs and 17 lncRNAs) were hypermethylated, 8 transcripts (5 mRNAs and 3 lncRNAs) were hypomethylated (>5-fold compared with sham) in the ischemic brain at 12 hours reperfusion. Inflammation, apoptosis, and transcriptional regulation are the major biological processes modulated by the poststroke differentially m⁶A methylated mRNAs. The m⁶A writers were unaltered, but the m⁶A eraser (fat mass and obesity-associated protein) decreased significantly after stroke compared with sham. Conclusions- This is the first study to show that stroke alters the cerebral m⁶A epitranscriptome, which might have functional implications in poststroke pathophysiology. Visual Overview- An online visual overview is available for this article.