MicroRNAs (miRNAs) play crucial roles in regulating innate and adaptive immunity in humans and animals. Infection with E. coli or S. aureus can cause inflammation of the mammary glands, which results in significant economic losses in dairy cattle. However, the regulatory mechanisms of miRNAs in response to E. coli or S. aureus infection in bovine mammary glands have not been thoroughly explored. To discover the differential expression of miRNA in bovine mammary gland challenged with E. coli or S. aureus, we performed miRNA sequencing on tissue samples. A total of 1838 miRNAs were identified, including 580 known-miRNAs (included in the miRbase database) and 1258 predicted novel miRNAs. The miRNA expression patterns indicated that, compared with control samples, 279 miRNAs and 305 miRNAs were differentially expressed miRNAs (DIE-miRNA) in S. aureus and E. coli infected tissues, respectively. Moreover, the results of comparison the DIE-miRNAs between the E. coli and S. aureus infected groups showed that 197 DIE-miRNAs are identical, 108 DIE-miRNAs are specific to the E. coli group, and 82 DIE-miRNAs are specific to the S. aureus group. Many DIE-miRNAs, such as bta-miR-144, bta-miR-451 and bta-miR-7863, might be the useful biomarkers of mastitis caused by E. coli and S. aureus. In addition, target genes of the DIE-miRNAs were predicted. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis indicated that these DIE-miRNAs are likely involved in many immune signaling pathways, including the Toll-like receptor signaling pathways, MAPK signaling pathway, cell adhesion molecules, TGF-β signaling pathway, leukocyte trans endothelial migration, cytokine-cytokine receptor interaction, and chemokine signaling pathways. This study has provided supportive evidence that miRNAs may serve as diagnostic biomarkers of mastitis in dairy cows, and suggests potentially of effective strategies to combat mastitis.

The bovine genetic resources in China are diverse, but their value and potential are yet to be discovered. To determine the genetic diversity and population structure of Chinese cattle, we analysed the whole genomes of 46 cattle from six phenotypically and geographically representative Chinese cattle breeds, together with 18 Red Angus cattle (RAN) genomes, 11 Japanese black cattle (JBC) genomes and taurine and indicine genomes available from previous studies. Our results showed that Chinese cattle originated from hybridization between Bos taurus and Bos indicus. Moreover, we found that the level of genetic variation in Chinese cattle depends upon the degree of indicine content. We also discovered many potential selective sweep regions associated with domestication related to breed-specific characteristics, with selective sweep regions including genes associated with coat colour (ERCC2, MC1R, ZBTB17 and MAP2K1), dairy traits (NCAPG, MAPK7, FST, ITFG1, SETMAR, PAG1, CSN3 and RPL37A), and meat production/quality traits (such as BBS2, R3HDM1, IGFBP2, IGFBP5, MYH9, MYH4 and MC5R). These findings substantially expand the catalogue of genetic variants in cattle and reveal new insights into the evolutionary history and domestication traits of Chinese cattle.

E. coli is the main causative agent of mastitis in dairy cows, but the mechanism of molecular regulation underlying the occurrence and development of mastitis has not yet been fully elucidated. In this study, an E. coli-induced mastitis model was created and RNASeq technology was used to measure the miRNA expression profiles at different times post-infection (0, 1, 3, 5, 7 dpi), as well as to screen for differentially expressed miRNA. The results show detection of 2416 miRNAs, including 628 known miRNAs and 1788 newly discovered miRNAs. A total of 200 differentially expressed miRNAs were found at different time points. Bioinformatics analysis showed that these differentially expressed miRNAs may regulate the occurrence and development of mastitis in dairy cows through seven signal transduction pathways, namely cytokine-cytokine receptor interaction, MAPK signaling pathway, chemokine signaling pathway, leukocyte transendothelial migration, T cell receptor signaling pathway, Toll-like receptor signaling pathway, and cell adhesion molecules. In addition, bta-miR-200a, bta-miR-205, bta-miR-122, bta-miR-182 and the newly discovered conservative_15_7229 might be involved in immune process in late stage of E. coli-induced mastitis. The results of this study lay the foundation for molecular network analysis of mastitis and molecular breeding of dairy cows.

MicroRNAs are small, single stranded, and noncoding RNAs that have been proven to be potent regulators of adipogenesis. However, the role of bta‐miR‐149‐5p in regulating bovine adipogenesis is still unclear. Expression profiling in different stages of adipogenesis revealed that bta‐miR‐149‐5p was enriched in the proliferation stage, and also on Day 9 of differentiation in bovine adipocytes. Our gain of function study showed that bta‐miR‐149‐5p can negatively regulate both bovine adipocyte proliferation and differentiation. Overexpression of bta‐miR‐149‐5p suppressed the expression of proliferation marker genes at both the messenger RNA (mRNA) and protein levels, markedly decreased the percentage of S‐phase cells, decreased the number of EdU‐stained cells, and substantially reduced adipocyte proliferation vitality in the cell count assay. Collectively, these findings elucidated that bta‐miR‐149‐5p inhibits adipocyte proliferation. Furthermore, overexpression of bta‐miR‐149‐5p also suppressed the expression of adipogenic genes at both the mRNA and protein levels, inhibited lipid accumulation, and reduced the secretion of adiponectin in bovine adipocytes. Furthermore, a luciferase activity assay explored how bta‐miR‐149‐5p targeted CRTCs (CRTC1 and CRTC2) directly. This targeting was further validated by the mRNA and protein level expression of CRTC1 and CRTC2, which were down regulated by bta‐miR‐149‐5p overexpression. Moreover, bta‐miR‐149‐5p indirectly targeted CRTC1 and CRTC2 through regulating their key transcription factors. Overexpression of bta‐miR‐149‐5p suppressed the expression of SMAD3, while enriched the expression of NRF1, which are the key transcription factors and proven regulators of CRTC1. Overexpression of bta‐miR‐149‐5p also repressed the expression of C/EBPγ, XBP1, INSM1, and ZNF263, which are the key regulators of CRTCs, at both the mRNA and protein levels. These findings suggest that bta‐miR‐149‐5p is a negative regulator of CRTC1 and CRTC2 both at transcriptional and posttranscriptional level. Taken together, these findings suggest that bta‐miR‐149‐5p can regulate adipogenesis, which implies that bta‐miR‐149‐5p could be a target for increasing intramuscular fat in beef cattle.