Analysis of differentially expressed circRNAs in longissimus muscle between castrated and intact male pigs.

Castration can reduce odor and fights in boars, but the carcass yield is reduced, and the intramuscular fat content is increased. Understanding its molecular mechanism is of great significance for production. Recent studies have shown that circular RNAs (circRNAs) play an important role(s) in the regulation of muscle development. To explore the effects of circRNAs on the development of longissimus dorsi (LD) muscle after castration, six Huainan male pigs were selected and three of which were randomly castrated. Six pigs were slaughtered when their body weight reached around 130 kg, and the LD muscle samples were collected. The differentially expressed circRNAs (DECs) were screened by high-throughput sequencing and functionally analyzed using the KEGG databases. DECs-miRNAs network was constructed, and the expression profiles of candidate circRNAs and their interactions with miRNAs were verified in porcine skeletal muscle satellite cells. The results showed that a total of 5866 circRNAs were obtained, and 370 DECs were identified in LD muscle between the castrated and intact groups (| logFoldchange | > 1, p <0.8). KEGG enrichment indicated that the parental genes for the DECs were mainly enriched in the pathways associated with muscle development, muscle fiber type transformation, and energy metabolism. There were 8 miRNAs and 69 circRNAs enriched in the DECs-miRNA network. circRNA_2241 and circRNA_4237 were selected for verification, which showed that these two circRNAs really existed and their expression profiles were consistent with the sequencing results. Further, preliminary analysis showed that circRNA_2241 interacted with miR-1, and testosterone promoted circRNA_2241 but inhibited miR-1 expression. These results confirmed that circRNAs might participate in the regulation of LD muscle development after castration by interacting with miRNAs, thereby providing new materials and references for analyses on the molecular mechanisms of castration on the regulation of muscle development.