Identification and evolutionary comparison of circular RNAs in five mammalian species and three organs.

Our analyses of circRNA repertoires across five species representing three mammalian lineages (marsupials, eutherians: rodents, primates) reveal that surprisingly few circRNAs arise from orthologous genes from different species. Even the circRNAs from shared loci are associated with young, recently active and species-specific transposable elements, rather than with common, ancient transposon integration events. These observations suggest that many circRNAs emerged convergently during evolution – as a byproduct of splicing in orthologs prone to transposable element insertion. Overall, our findings argue against widespread functional circRNA conservation.我们针对代表三大哺乳动物演化支（有袋类、真兽类：啮齿类、灵长类）的五个物种的环状RNA（circular RNA, circRNA）组开展分析，结果显示不同物种的同源基因（orthologous gene）所产生的环状RNA数量少得出人意料。即便源自共享基因座的环状RNA，也与年轻、新近活跃且物种特异性的转座因子（transposable element, TE）相关，而非与普遍存在的古老转座子整合事件相关。上述观测结果表明，大量环状RNA在演化过程中趋同产生——这是易于发生转座因子插入的同源基因剪接过程所产生的副产物。总体而言，我们的研究结果不支持环状RNA存在广泛功能保守性的论断。