Transcriptome-wide map of m6A circRNAs identified in hypoxic pulmonary hypertension rat model

Hypoxic pulmonary hypertension (HPH) is a lethal disease. CircRNAs and m6A circRNAs have been reported to be associated with cancer progression, but the ex-pression profiling of m6A circRNAs has not been identified in HPH. This study was to investigate the transcriptome-wide map of m6A circRNAs in HPH. In this study, hy-poxia-induced PH rat model was established. Total RNA was extracted and purified from lungs of rats, then circRNAs were detected and annotated by RNA-seq analysis. m6A RNA Immunoprecipitation (MeRIP) was performed following rRNA depletion, and RNA-seq library was constructed. CircRNA–miRNA–mRNA co-expression net-work was also constructed. In vitro, total m6A was measured. m6A circXpo6 and m6A circTmtc3 were detected in pulmonary artery smooth muscle cells (PASMCs) and pulmonary artery endothelial cells (PAECs) exposed to 21% O2 and 1% O2 for 48 h, respectively. m6A abundance in 166 circRNAs was significantly upregulated and m6A abundance in 191 circRNAs was significantly downregulated in lungs of HPH rats. m6A abundance in circRNAs was significantly reduced in hypoxia in vitro. m6A circRNAs were mainly derived from single exons of protein-coding genes. m6A influ-enced the circRNA–miRNA–mRNA co-expression network in hypoxia. m6A circX-po6 and m6A circTmtc3 were downregulated in hypoxia. In general, our study firstly identified the transcriptome-wide map of m6A circRNAs in HPH. m6A level in circRNAs was decreased in lungs of HPH rats and in PASMCs and PAECs exposed to hypoxia. Downregulated or upregulated m6A level influenced circRNA–miRNA–mRNA co-expression network in HPH. Moreover, we firstly identified two downreg-ulated m6A circRNAs in HPH: circXpo6 and circTmtc3. We suggested that m6A circRNAs may be used as a potential diagnostic marker or therapy target in the future.