Abstract 12012: Dysregulated Adenosine Methylation of RNA in Myocardial Ischemia

Introduction: Emerging evidence suggests that post-transcriptional modifications of mRNAs are vital to their stability, nuclear export, cellular compartmentalization, translation to proteins, degradation and stem cell pluripotency. However, such mechanisms remain unexplored in mature post-mitotic tissues such as the mammalian myocardium, especially under its pathophysiological remodeling. Here, we investigated the role of N6-methyladenosine (m6A), the most prevalent chemical modification in RNA, in myocardial ischemia. Methods and Results: We studied post-mortem human tissues, murine and swine models of myocardial ischemia and demonstrated for the first time that m6A methylation of mRNA in the ischemic left ventricle (LV) is significantly increased when compared with non-ischemic LV. We found that increase in m6A methylation is conserved in human, pig and mice and have global effect in post-ischemic cardiac remodeling, affecting mRNA, miRNA and protein expressions, and myocyte function. We identified that the expression of m6A demethylase, fat mass and obesity-associated protein (FTO) is decreased in post-ischemic human and mouse myocardium. Using loss-of-function gain-of-function studies in isolated primary adult rat cardiomyocytes, we identified FTO as a direct regulator of m6A methylation, SERCA2a expression and cardiomyocyte function including Ca 2+ transient, decay and sarcomere shortening. Remarkably, in primary cardiomyocytes under hypoxia stress, FTO expression was down regulated resulting in increase in mRNA methylation, decrease in SERCA2a expression and compromised cardiomyocyte function, all of which was restored by adenovirus-mediated overexpression of FTO under hypoxia. Finally, using methylated RNA pull-down assay of RNA from human ischemic and control LV tissues, we have demonstrated that SERCA mRNA is hypermethylated under ischemia and that SERCA demethylation by FTO is essential for SERCA mRNA expression and protein synthesis. Conclusions: We have discovered a novel pathomechanism by which FTO, a RNA demethylase, plays a critical role in cardiac homeostasis and cardiomyocyte function under ischemia. Our discovery opens up a new paradigm for our understanding of post-ischemic cardiac remodeling.