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

Abstract

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.