Circular RNA identified from Peg3 and Igf2r

Circular RNA is a newly discovered class of non-coding RNA generated through the back-splicing of linear pre-mRNA. In the current study, we characterized two circular RNAs that had been identified through NGS-based 5’RACE experiments. According to the results, the Peg3 locus contains a 214-nucleotide-long circular RNA, circPeg3, that is detected in low abundance from the neonatal brain, lung and ovary. In contrast, the Igf2r locus contains a group of highly abundant circular RNAs, circIgf2r, showing multiple forms with various exon combinations. In both cases, the expression patterns of circPeg3 and circIgf2r among individual tissues are quite different from their linear mRNA counterparts. This suggests potential unique roles played by the identified circular RNAs. Overall, this study reports the identification of novel circular RNAs specific to mammalian imprinted loci, suggesting that circular RNAs are likely involved in the function and regulation of imprinted genes.环状RNA（Circular RNA）是一类新近发现的非编码RNA（non-coding RNA），通过线性前体mRNA（linear pre-mRNA）的反向剪接（back-splicing）产生。本研究对经基于下一代测序（Next Generation Sequencing, NGS）的5'末端快速扩增（5'-Rapid Amplification of cDNA Ends, 5’RACE）实验鉴定得到的两种环状RNA进行了系统表征。结果显示，Peg3基因座存在一条长度为214个核苷酸的环状RNA circPeg3，该分子在新生脑、肺及卵巢中呈低丰度表达。与之相对，Igf2r基因座存在一组高丰度的环状RNA circIgf2r，其包含多种带有不同外显子组合的亚型。在两种情形下，circPeg3与circIgf2r在各组织中的表达模式均与其对应的线性mRNA存在显著差异，这暗示所鉴定的环状RNA可能发挥独特的生物学功能。总体而言，本研究报道了一类特异性靶向哺乳动物印记基因座的新型环状RNA，表明环状RNA大概率参与印记基因的功能与调控过程。