Abstract
Circular RNAs (circRNAs), which were discovered as a special class of endogenous non-coding RNAs, have recently shown huge capabilities as gene regulators in different species in a wide variety of organisms including viruses, plants, archaea and animals. These circRNAs mainly arise from exons or introns in different combinations by special selective splicing and are enriched in cytoplasm. Apart from that, circRNAs usually display patterns of cell-type, tissue-type and developmental-stage specific expression in eukaryotic transcriptome. These findings hint at the vital function of circRNAs in development and diseases. Herein, we summarize the current understanding of the molecular characteristics of circRNAs and discuss their proposed functions and mechanism-of-action in human diseases, animals as well as botanics.