Emerging Roles of Heat-Induced circRNAs Related to Lactogenesis in Lactating Sows

Abstract

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 for further study. 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, long-term heat stress (HS) resulted in a greater concentration of serum HSP70, LDH, and IgG, as well as decreased levels of COR, SOD, and PRL. HS reduced the total solids, fat, and lactose of sow milk, and HS significantly depressed CSNas1, CSNas2, and CSNk biosynthesis. Transcriptome sequencing of lactating porcine mammary glands identified 42 upregulated and 25 downregulated transcripts in HS vs. control. Functional annotation of these differentially-expressed transcripts revealed four heat-induced genes involved in lactation. Moreover, 29 upregulated and 21 downregulated circRNA candidates were found in response to HS. Forty-two positively correlated circRNA-mRNA expression patterns were constructed between the four lactogenic genes and differentially expressed circRNAs. Five circRNA-miRNA-mRNA post-transcriptional networks were identified involving genes in the HS 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.

Genome-wide identification and functional prediction of circular RNAs in response to heat stress in Chinese Holstein cows

“…Wang et al [29] reported that in cows circCSN1S2 was downregulated during HS condition. Whereas, Sun et al [31] reported circCSN1S1_1 and circCSN1S1_2 which are two circRNAs processed from one host gene, and showed contrasting expression trend during HS condition in sows. This inconsistent expression trend may relate to the exact lactation stage of cows, which need to be considered in further study.…”

MicroRNAs as Biomarkers for Animal Health and Welfare in Livestock

“…The miRNA exosome cargo purified from milk samples was sequenced, leading to the identification of 10 miRNAs that were upregulated, and 16 that were downregulated, in the GPS-treated group compared with the control group. These miRNAs were suggested to act as potential regulators of immune functions (136). The expression levels of miR-30a and let-7d were altered by GPS supplementation, again highlighting their essential role in milk.…”

Circular RNAs Are Regulators of Diverse Animal Transcriptomes: One Health Perspective

“…RNA sequencing analysis by Sun et al (2020) revealed heat stress also significantly decreased the levels of casein family genes, CSN1S1, CSN1S2, CSN3 in swine. The analysis of circRNA transcriptomes between non-heat-stressed and heatstressed sows revealed 50 DE circRNAs between the groups.…”

“…The authors of a more recent study decided to look into the circRNA profiles in mammary gland of lactating sows under heat stress (Sun et al, 2020), since it was reported that circRNAs are expressed in bovine mammary glands and could regulate milk content (Zhang et al, 2016). Even though swine milk is not a primary product for human consumption, quality and yield of milk in lactating sows plays an important role for feeding viable offspring raised for meat.…”