Emerging roles of heat-induced circRNAs related to lactogenesis in lactating sows

Heat stress negatively influences milk production and disrupts normal physiological activity of lactating sows, but the precious mechanisms by which hyperthermia adversely affects milk synthesis in sows still remain further explored. Circular RNAs are a novel class of non-coding RNAs with regulatory functions in various physiological and pathological processes. The expression profiles and functions of circRNAs of sows in lactogenesis remain largely unknown. In the present study, transcriptome sequencing of lactating porcine mammary glands identified 279 upregulated and 185 downregulated transcripts in heat stress vs. control. Functional annotation of these differentially-expressed transcripts revealed 12 heat-induced genes involved in lactation. Moreover, 29 upregulated and 21 downregulated circRNA candidates were found in response to heat stress. 87 positively correlated circRNA-mRNA expression patterns were constructed between the 12 lactogenic genes and differentially expressed circRNAs. 33 circRNA-miRNA-mRNA post-transcriptional networks were identified involving genes in the heat stress response of lactating sows. In this study we establish a valuable resource for circRNA biology in sow lactation. Analysis of a circRNA-miRNA-mRNA network further uncovered a novel layer of post-transcriptional regulation that could be used to improve sow milk production.