CircRNA8220 Sponges MiR-8516 to Regulate Cell Viability and Milk Synthesis via Ras/MEK/ERK and PI3K/AKT/mTOR Pathways in Goat Mammary Epithelial Cells

Circular RNA_015343 sponges microRNA-25 to regulate viability, proliferation, and milk fat synthesis of ovine mammary epithelial cells via INSIG1

In our previous study, circ_015343 was found to inhibit the viability and proliferation of ovine mammary epithelial cells (OMECs) and the expression levels of milk fat synthesis marker genes, but the regulatory mechanism underlying the processes is still unclear. Accordingly in this study, the target relationships between circ_015343 with miR-25 and between miR-25 with insulin induced gene 1 (INSIG1) were verified, and the functions of miR-25 and INSIG1 were investigated in OMECs. The dual-luciferase reporter assay revealed that miR-25 mimic remarkably decreased the luciferase activity of circ_015343 in HEK293T cells cotransfected with a wild-type vector, while it did not change the activity of circ_015343 in HEK293T cells cotransfected with a mutant vector. These suggest that cic_015343 can adsorb and bind miR-25. The miR-25 increased the viability and proliferation of OMECs, and the content of triglycerides in OMECs. In addition, INSIG1 was found to be a target gene of miR-25 using a dual-luciferase reporter assay. Overexpression of INSIG1 decreased the viability, proliferation, and level of triglycerides of OMECs. In contrast, the inhibition of INSIG1 in expression had the opposite effect on activities and triglycerides of OMECs with overexpressed INSIG1. A rescue experiment revealed that circ_015343 alleviated the inhibitory effect of miR-25 on the mRNA and protein abundance of INSIG1. These results indicate that circ_015343 sponges miR-25 to inhibit the activities and content of triglycerides of OMECs by upregulating the expression of INSIG1 in OMECs. This study provided new insights for understanding the genetic molecular mechanism of lactation traits in sheep.

Progress in epigenetic regulation of milk synthesis, with particular emphasis on mRNA regulation and DNA methylation

Inadequate milk secretion and a lack of nutrients in humans and mammals are serious problems. It is of great significance to clarify the mechanisms of milk synthesis and treatment methods. Epigenetic modification, represented by RNA methylation, is an important way of gene expression regulation that profoundly affects human gene expression and participates in various physiological and pathological mechanisms. Epigenetic disorders also have an important impact on the production and secretion of milk. This review systematically summarized the research results of epigenetics in the process of lactation in PubMed, Web of Science, NSTL, and other databases and reviewed the effects of epigenetics on human and mammalian lactation, including miRNAs, circRNAs, lncRNAs, DNA methylations, and RNA methylations. The abnormal expression of miRNAs was closely related to the synthesis and secretion of milk fat, milk protein, and other nutrients in the milk of cattle, sheep, and other mammals. MiRNAs are also involved in the synthesis of human milk and the secretion of nutrients. CircRNAs and lncRNAs mainly target miRNAs and regulate the synthesis of nutrients in milk by ceRNA mechanisms. The abnormal expression of DNA and RNA methylation also has an important impact on milk synthesis. Epigenetic modification has the potential to regulate the milk synthesis of breast epithelial cells. Analyzing the mechanisms of human and mammalian milk secretion deficiency and nutrient deficiency from the perspective of epigenetics will provide a new perspective for the treatment of postpartum milk deficiency in pregnant women and mammalian milk secretion deficiency.

The emerging roles of circRNAs in traits associated with livestock breeding

Many indicators can be used to evaluate the productivity and quality of livestock, such as meat and milk production as well as fat deposition. Meat and milk production are measures of livestock performance, while fat deposition affects the taste and flavor of the meat. The circRNAs, are non-coding RNAs, that are involved in the regulation of all these three traits. We review the functions and mechanisms of circRNAs in muscle and fat development as well as lactation to provide a theoretical basis for circRNA research in animal husbandry. Various phenotypic changes presented in livestock may be produced by different circRNAs. Our current concern is how to use the roles played by circRNAs to our advantage to produce the best possible livestock. Hence, we describe the advantages and disadvantages of knockout techniques for circRNAs. In addition, we also put forward our thoughts regarding the mechanism and network of circRNAs to provide researchers with novel ideas of how molecular biology can help us advance our goals in animal farming. This article is categorized under: RNA in Disease and Development > RNA in Disease RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications RNA Interactions with Proteins and Other Molecules > Protein-RNA Recognition RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes.

miR-27a-3p relieves heat stress-induced mitochondrial damage and aberrant milk protein synthesis through MEK/ERK pathway in BMECs

With global warming, heat stress has become a primary factor that compromises the health and milk quality of dairy cows. Here, we investigated the function and underlying regulatory mechanism of miR-27a-3p in bovine mammary epithelial cells (BMECs) under heat-stress conditions. The current study showed that miR-27a-3p could prevent heat stress-induced BMEC oxidative stress and mitochondrial damage by regulating the balance between mitochondrial fission and fusion processes. Importantly, we found that miR-27a-3p could increase cell proliferation under heat stress conditions by regulating the MEK/ERK pathway and cyclin D1/E1. Interestingly, miR-27a-3p is also involved in the regulation of milk protein synthesis-related protein expression, such as CSN2 and ELF5. Inhibition of the MEK/ERK signaling pathway by AZD6244 blocked the regulatory function of miR-27a-3p in cell proliferation and milk protein synthesis in BMECs under heat stress conditions. Our findings demonstrated that miR-27a-3p protects BMECs from heat stress-induced oxidative stress and mitochondrial damage through the MEK/ERK pathway, thereby promoting BMECs proliferation and lactation in dairy cows. The potential regulatory mechanism of miR-27a-3p in attenuating heat stress-induced apoptosis and lactation defect in BMECs.

Lnc-TRTMFS promotes milk fat synthesis via the miR-132x/RAI14/mTOR pathway in BMECs

As an important index to evaluate the quality of milk, milk fat content directly determines the nutrition and flavor of milk. Recently, growing evidence has suggested that long noncoding RNAs (lncRNAs) play important roles in bovine lactation, but little is known about the roles of lncRNAs in milk fat synthesis, particularly the underlying molecular processes. Therefore, the purpose of this study was to explore the regulatory mechanism of lncRNAs in milk fat synthesis. Based on our previous lncRNA-seq data and bioinformatics analysis, we found that Lnc-TRTMFS (transcripts related to milk fat synthesis) was upregulated in the lactation period compared to the dry period. In this study, we found that knockdown of Lnc-TRTMFS significantly inhibited milk fat synthesis, resulting in a smaller amount of lipid droplets and lower cellular triacylglycerol levels, and significantly decreased the expression of genes related to adipogenesis. In contrast, overexpression of Lnc-TRTMFS significantly promoted milk fat synthesis in bovine mammary epithelial cells (BMECs). In addition, Bibiserv2 analysis showed that Lnc-TRTMFS could act as a molecular sponge for miR-132x, and retinoic acid induced protein 14 (RAI14) was a potential target of miR-132x, which was further confirmed by dual-luciferase reporter assays, quantitative reverse transcription PCR, and western blots. We also found that miR-132x significantly inhibited milk fat synthesis. Finally, rescue experiments showed that Lnc-TRTMFS could weaken the inhibitory effect of miR-132x on milk fat synthesis and rescue the expression of RAI14. Taken together, these results revealed that Lnc-TRTMFS regulated milk fat synthesis in BMECs via the miR-132x/RAI14/mTOR pathway.

Tissue-Specific Expression of Circ_015343 and Its Inhibitory Effect on Mammary Epithelial Cells in Sheep

Circular RNAs (circRNAs) are a kind of non-coding RNA that have an important molecular function in mammary gland development and lactation of mammals. In our previous study, circ_015343 was found to be highly expressed in the ovine mammary gland tissue at the peak-lactation period by using RNA sequencing (RNA-seq). In the present study, the authenticity of circ_015343 was confirmed by using reverse transcriptase-polymerase chain reaction (RT-PCR) analysis and Sanger sequencing. The circ_015343 was derived from the complete 10 exons of aminoadipic semialdehyde synthase (AASS), ranging from exon 2 to exon 11 and mainly located in cytoplasm of ovine mammary epithelial cells. The circRNA was found to be expressed in eight ovine tissues, with the highest expression level in the mammary gland and the least expression in Longissimus dorsi muscle. The circ_015343 had a lower level of expression in a sheep breed with higher milk yield and milk fat content. The disturbed circ_015343 increased the viability and proliferation of the ovine mammary epithelial cells. The inhibition of circ_015343 also increased the expression levels of three milk fat synthesis marker genes: acetyl-coenzyme A carboxylase alpha (ACACA), fatty acid-binding protein 4 (FABP4), and sterol regulatory element-binding protein 1 (SREBP1), as well as three proliferation-related genes: cyclin dependent kinase 2 (CDK2), cyclin dependent kinase 4 (CDK4) and proliferating cell nuclear antigen (PCNA), but decreased the expression level of its parent gene AASS. A circRNA-miRNA-mRNA interaction network showed that circ_015343 would bind some microRNAs (miRNAs) to regulate the expression of functional genes related to the development of mammary gland and lactation. This study contributes to a better understanding of the roles of circ_015343 in the mammary gland of sheep.

Enhancing or inhibiting apoptosis? The effects of ucMSC-Ex in the treatment of different degrees of traumatic pancreatitis

The animal models of traumatic pancreatitis (TP) were established to evaluate the specific mechanisms by which umbilical cord mesenchymal stem cell-derived exosomes (ucMSC-Ex) exert therapeutic effects. Sixty four rats were randomly divided into eight groups, including TP groups with three different degrees and relevant groups with ucMSC-Ex treated. The degrees of pancreatic tissue injury were evaluated by Histological Examination. Furthermore, enzyme-linked immunosorbent assay were applied to evaluate the activity of pancreatic enzymes and levels of inflammatory factors in serum. Finally, the apoptotic effects of each group were evaluated by TUNEL, western blot (WB), and real time fluorescence quantitative polymerase chain reaction (RT-qPCR). The pancreatic histopathological score and serum amylase and lipase levels gradually increased in various degrees of TP and the levels in the treatment group were all significantly decreased. The apoptosis index gradually increased in each TP group and significantly decreased in the treatment group in TUNEL results. WB and RT-qPCR showed the same trend, that bax and caspase-3 gradually increased and bcl-2 gradually decreased in TP groups. Compared with TP groups, the expression of bax and caspase-3 were lower while bcl-2 expression was higher in the treatment group. ucMSC-Ex suppressed the inflammatory response and inhibited pancreatic acinar cell apoptosis to promote repair of injured pancreatic tissue.

CircEZH2 Regulates Milk Fat Metabolism through miR-378b Sponge Activity

Simple Summary

Heat stress has seriously threatened the performance and health of dairy cows and has become one of the most important factors restricting the development of the dairy industry. In our previous study, we found that heat stress markedly altered the expression patterns of circRNAs in dairy cow’s mammary gland tissue, and heat-induced circRNAs participated in the regulation of milk fat metabolism through competing endogenous RNA (ceRNA) networks. Therefore, we evaluated the roles of heat-induced circEZH2 in the regulation of milk fat metabolism in this study. In more detail, we found that circEZH2 affects the proliferation, apoptosis, and lipid metabolism of mammary gland epithelial cells, and successfully verified the targeting relationship of circEZH2-bta-miR378b-LPL and circEZH2-bta-miR378b-CD36. This experiment expands the basic data on the role of circRNA in milk fat regulation, and provides a theoretical basis for alleviating heat stress in dairy cows.

Abstract

In this study, we evaluated the roles of heat-induced circEZH2 in the regulation of milk fat metabolism. CircEZH2 overexpression increased HC11 cell proliferation and decreased apoptosis. These changes were accompanied by increased expression of proliferation marker proteins (PCNA, Cyclin D, and Cyclin E) and the anti-apoptotic protein Bcl2, while expression of the pro-apoptotic proteins Bax and cleaved-caspase was reduced. SiRNA-mediated silencing of EZH2 in HC11 cells had the opposite effects. CircEZH2 overexpression promoted the uptake of a fluorescent fatty acid (Bodipy) as well as expression of the fatty acid transport-related protein CD36, lipolysis-related protein LPL, and unsaturated fatty acid metabolism-related proteins FADS1 and SCD1. Dual luciferase reporter assays verified the targeting relationship of the two ceRNA networks, circEZH2-miR378b-LPL and circEZH2-miR378b-CD36. This information provides further clarification of the role of circRNAs in milk fat regulation in addition to a theoretical basis for alleviating the effects of heat stress on milk production by dairy cows.

Progress on the Regulation of Ruminant Milk Fat by Noncoding RNAs and ceRNAs

Milk fat is not only a key factor affecting the quality of fresh milk but also a major target trait forbreeding. The regulation of milk fat involves multiple genes, network regulation and signal transduction. To explore recent discoveries of pathway regulation, we reviewed the published literature with a focus on functional noncoding RNAs and epigenetic regulation in ruminants. Results indicate that miRNAs play key roles in the regulation of milk fat synthesis and catabolism in ruminants. Although few data are available, merging evidence indicates that lncRNAs and circRNAs act on milk fat related genes through indirect action with microRNAs or RNAs in the ceRNA network to elicit positive effects on transcription. Although precise regulatory mechanisms remain unclear, most studies have focused on the regulation of the function of target genes through functional noncoding RNAs. Data to help identify factors that can regulate their own expression and function or to determine whether self-regulation involves positive and/or negative feedback are needed. Despite the growing body of research on the role of functional noncoding RNA in the control of ruminant milk fat, most data are still not translatable for field applications. Overall, the understanding of mechanisms whereby miRNA, lncRNA, circRNA, and ceRNA regulate ruminant milk fat remains an exciting area of research.

Functional Role of circRNAs in the Regulation of Fetal Development, Muscle Development, and Lactation in Livestock

circRNAs are a class of endogenous noncoding RNA molecules with closed loop structures. They are mainly responsible for regulating gene expression in eukaryotic cells. With the emergence of high-throughput RNA sequencing (RNA-Seq) and new types of bioinformatics tools, thousands of circRNAs have been discovered, making circRNA one of the research hotspots. Recent studies have shown that circRNAs play an important regulatory role in the growth, reproduction, and formation of livestock products. They can not only regulate mammalian fetal growth and development but also have important regulatory effects on livestock muscle development and lactation. In this review, we briefly introduce the putative biogenic pathways and regulatory functions of circRNA and highlight our understanding of circRNA and its latest advances in fetal development, muscle development, and lactation biogenesis as well as expression in livestock. This review will provide a theoretical basis for the research and development of related industries.