Identification of potential key circular RNAs associated with Escherichia coli-infected bovine mastitis using RNA-sequencing: preliminary study results.

Escherichia coli (E. coli) is commonly found in dairy farms and can invade mammary gland tissue, often causing acute clinical mastitis. Mammary infections with E. coli have shown a wide range of clinical signs, causing abnormal appearance of the milk, udder inflammation and systemic signs of illness. Circular RNA is a class of endogenous non-coding RNA that plays an important role in the occurrence and development of various inflammatory diseases. However, there is little information on the circRNA associated with bovine mastitis. In this study investigated the involvement of circRNAs in bovine mastitis through the construction of an E. coli-infected bovine mastitis model by injecting of E. coli into the mammary gland of dairy cows, using healthy gland mammary tissue as a control (M_C). High-throughput RNA-seq was performed on the E. coli-infected mammary gland tissue (M_E) and differentially expressed circRNAs between theM_C and M_E groups, followed by an analysis of their potential functions using bioinformatics methods. A total of 164 differentially expressed circRNAs were identified, including 92 downregulated circRNAs and 72 upregulated circRNAs. As shown by Gene Ontology enrichment analysis these DE circRNAs were mostly enriched in ras protein signal transduction, cytoplasmic vesicle parts, and enzyme binding, and Kyoto Encyclopedia of Genes and genome singal pathway enrichment analysis indicated significant associations with phagosome signal pathway. Additionally, the expression of bovine mastitis-related circRNAs, including novel_circRNA_0000128, novel_circRNA_0011103, novel_circRNA_0012656, novel_circRNA_0015099, novel_circRNA_005648, novel_circRNA_000074, and novel_circRNA_0011796 were verified via quantitative reverse-transcription polymerase chain reaction (RT-qPCR). These results provide a new direction for further investigation of the molecular mechanisms underlying bovine mastitis.