Biological functions of circRNAs and their progress in livestock and poultry

Abstract

CircRNAs are a class of newly discovered RNAs extensively expressed in eukaryotic cells (Jeck et al., 2013). Compared with conventional linear RNAs (containing 5′ and 3′ ends), circRNAs are covalently closed RNA molecules. It was recognized as a class of functional RNA that differs from miRNA, piRNA and lncRNA due to its character of circularity (Xu, Wu, Han, Zhao, & Song, 2017). CircRNAs were first found in RNA viruses as a viroid as early as in 1976 (Sanger, Klotz, Riesner, Gross, & Kleinschmidt, 1976). And then in 1986, it was also founded that the HDV, an animal virus, has a circRNA genome, which were considered to be a characteristic of viroids (Kos, Dijkema, Arnberg, van der Meide, & Schellekens, 1986). Due to limitation of technology at that time, circRNAs were less reported and were once considered as by-products of mis-splicing or regarded as a meaningless abnormally cut RNA, which never got any attention by some researchers because traditional molecular techniques employed in RNA analysis were not able to detect circRNAs because they did not have cap of 5′ end and tail of 3′ end (Jeck & Sharpless, 2014). It was not until 1991 that endogenous circRNAs were demonstrated in human cells, which originated from exons (Nigro et al., 1991). Since then, with advancement of bioinformatics analysis and RNA sequencing technologies, circRNA has attracted more and more attention of many scientists because it has been reported to be ubiquitously present in eukaryotic organisms and have longer half-lives than linear RNAs (Memczak et al., 2013;

Emerging functions of circular RNA in the regulation of adipocyte metabolism and obesity

“…The expression levels of circRNAs in tissues are low, with tissue-specific and cell-specific expression patterns [ 27 – 29 ]. Although circRNAs are closely related to a series of physiological processes in animals, the biogenesis mechanism of circRNAs in different animals has certain differences [ 30 ]. Previous studies have confirmed that circRNAs are involved in adipogenesis and lipolysis in adipose tissue, and also play regulatory roles in lipid metabolism in hepatocytes [ 31 ].…”

Identification of circular RNAs expression pattern in caprine fetal fibroblast cells exposed to a chronic non-cytotoxic dose of graphene oxide-silver nanoparticle nanocomposites

“…CircRNAs is a large class of non-coding RNA which has regulatory roles on different molecules including mRNAs, non-coding RNAs, DNAs and proteins ( Chen, 2020 ) as well as on various biological processes ( Huang et al, 2020 ; Yang et al, 2021 ). To understand how nanotoxicity interferes the ex-pression pattern and functions of circRNAs, we have induced GO-AgNPs mediated chronic toxicity in CFFCs.…”

“…The circRNAs are functionally different from miRNA, piRNA and lncRNA, and play an important role as microRNA sponges, regulating gene splicing and transcription, as well as RNA-binding protein sponges and protein/peptide translating (Patop et al, 2019). It also showed close involvement in a series of physiological processes that are regulating fetal growth, muscle formation, and lactation in mammals (Huang et al, 2020;He et al, 2021). CircRNAs are also found to be important in the regulation of post-transcriptional gene expression (Hansen et al, 2013).…”

Regulation of Non-Coding RNA in the Growth and Development of Skeletal Muscle in Domestic Chickens

“…Currently, the methods used to identify the presence of circRNAs mainly include PCR, northern blot, etc. However, it is still a challenge to annotate the function of circRNAs [ 133 ]. The commonly used loss-of-function experiments are more limited in the process of verifying the function of circRNAs.…”