Characterization of circular RNAs in bovine mammary epithelial cells induced by Escherichia coli LPS

Abstract The rise of multi-omics technology in recent years provides convenient for in-depth study of the pathogenesis of dairy cow mastitis, and circRNAs, as endogenous non-coding RNAs, are expected to become molecular targets to study the pathogenesis of dairy cow mastitis. LPS, as a component of the outer wall of E. coli cell wall, is a common endotoxin in the construction of inflammatory models. The objective of this study is to identified and compared circular RNAs (circRNAs) from bovine mammary epithelial cells (bMECs) between the control and LPS groups. The expression profiles of circRNAs were obtained by high-throughput sequencing (RNA-seq) based on the construction of bMECs - LPS inflammation model, with control group (n = 3) and LPS group (n = 3) cell RNA as samples. After analysis, we identified 4323 circRNAs, ranging from 63 bp to 96387 bp. Chromosome 5 had most circRNAs, containing 259 circRNAs. Furthermore, 87.42% of the circRNAs belonged to sense-overlapping circRNA. CircRNAs contains different number of exons, ranging from 1 to 43, and most of cirsRNAs harbored 1 to 5 exons. Compared with the negative control (NC) group, 841 circRNAs with significantly different expressions (DE) in the LPS group (10 μg/mL), including 400 upregulated and 441 downregulated circRNAs. Enrichment analysis revealed the enrichment of circRNAs in methylation, such as positive regulation of G1/S transition of the mitotic cell cycle, histone methyltransferase activity (H3-K27 specific), and DNA methylation. The significantly enriched pathways further indicate that circRNAs play important roles in immunoreaction, such as hippo signaling pathway – fly, AMPK signaling pathway, and Fc gamma R-mediated phagocytosis. This study revealed the expression profile and characteristics of circRNAs in bMECs induced by LPS, and providing information for studying circRNA functions and mechanisms underlying mastitis, which suggesting a new avenue to investigate the regulatory mechanisms of mastitis.