Transcriptome RNA Sequencing Reveals That Circular RNAs Are Abundantly Expressed in Embryonic Breast Muscle of Duck

Simple Summary Research into the genetic mechanisms of skeletal muscle development in ducks is of great significance to the breeding and industrialization of indigenous ducks in China. This study examined the crucial candidates during two developmental stages of duck embryonic breast muscles by circular RNA sequencing. There were 16,622 circular RNAs detected between embryonic day 13 (E13) and embryonic day 19 (E19), of which 260 showed differential expression. Additionally, we examined the protein-protein interaction (PPI) with the parental genes of the differentially expressed circular RNAs, as well as the enriched GO terms and KEGG pathways. In addition, we selected one circular transcript of the growth arrest-specific gene 2 (GAS2), or circGAS2-2, to perform functional validations in duck embryonic myoblasts. The results showed that circGAS2-2 accelerated cell cycling and promoted the proliferation of myoblasts. Our results supplement the duck circular RNA database and demonstrate that circular RNAs are abundantly and differentially expressed during duck skeletal muscle development. Circular RNAs are widespread in various species and have important roles in myogenesis. However, the circular RNAs involved in breast muscle development in ducks have not yet been studied. Here, to identify circular RNAs during duck skeletal muscle development, three pectorales from Shan Ma ducks at E13 and E19, which represent undifferentiated and differentiated myoblasts, respectively, were collected and subjected to RNA sequencing. A total of 16,622 circular RNAs were identified, of which approximately 80% were exonic circular RNAs and 260 were markedly differentially expressed between E19 and E13. The parental genes of the differentially expressed circular RNAs were significantly enriched in muscle-related biological processes. Moreover, we found that the overexpression of circGAS2-2 promoted cell cycle progression and increased the proliferation viability of duck primary myoblasts; conversely, knockdown of circGAS2-2 retarded the cell cycle and reduced the proliferation viability of myoblasts. Taken together, our results demonstrate that circular RNAs are widespread and variously expressed during the development of duck skeletal muscle and that circGAS2-2 is involved in the regulation of myogenesis.