Comprehensive analysis of differentially expressed circRNAs and ceRNA regulatory network in porcine skeletal muscle

Circular RNA (circRNA), a novel class of non-coding RNA, has a closed-loop structure with important functions in skeletal muscle growth. The purpose of this study was to investigate the role of differentially expressed circRNAs (DEcircRNAs), as well as the DEcircRNA-miRNA-mRNA regulatory network, at different stages of porcine skeletal muscle development. Here, we present a panoramic view of circRNA expression in porcine skeletal muscle from Large White and Mashen pigs at 1, 90, and 180 days of age. We identified a total of 5819 circRNAs. DEcircRNA analysis at different stages showed 327 DEcircRNAs present in both breeds. DEcircRNA host genes were concentrated predominately in TGF-β, MAPK, FoxO, and other signaling pathways related to skeletal muscle growth and fat deposition. Further prediction showed that 128 DEcircRNAs could bind to 253 miRNAs, while miRNAs could target 945 mRNAs. The constructed ceRNA network plays a vital role in skeletal muscle growth and development, and fat deposition. Circ_0015885/miR-23b/SESN3 in the ceRNA network attracted our attention. miR-23b and SESN3 were found to participate in skeletal muscle growth regulation, also playing an important role in fat deposition. Using convergent and divergent primer amplification, RNase R digestion, and qRT-PCR, circ_0015885, an exonic circRNA derived from Homer Scaffold Protein 1 (HOMER1), was confirmed to be differentially expressed during skeletal muscle growth. In summary, circ_0015885 may further regulate SESN3 expression by interacting with miR-23b to function in skeletal muscle. This study not only enriched the circRNA library in pigs, but also laid a solid foundation for the screening of key circRNAs during skeletal muscle growth and intramural fat deposition. In addition, circ_0015885/miR-23b/SESN3, a new network regulating skeletal muscle growth and fat deposition, was identified as important for increasing the growth rate of pigs and improving meat quality.