The landscape of circular RNAs and mRNAs in bovine milk exosomes

RNA in milk exosome can be absorbed in the mammalian gastrointestinal tract and plays important regulatory function. Circular RNA is one kind of covalently closed RNA molecule derived by backsplicing that have important physiological functions. In the present study, we examine in detail the landscape of circular RNA and mRNA of the bovine milk exosome in order to provide the molecular basis of functional component of bovine milk. The total RNAs were isolated from exosome in bovine colostrum and mature milk. High throughput RNA-sequencing were used to characterize the profiles of the circular RNAs and mRNAs. 2059 distinct circular RNAs were identified from milk exosomes, most of which were expressed either specific in colostrum or in mature milk exosomes. Circular RNA host genes were enriched for genes involved in cytoplasm, endoplasmic reticulum, transport, and transcription factor. The species of mRNA presented in milk exosome were consistent, where 18,612 mRNAs were common to both kinds of exosome. The circular RNAs profile of colostrum or mature milk exosomes differed greatly. As RNAs in milk exosome can be absorbed and function in receipt cells, these RNAs might act as a novel regulatory nutrient for infant and adult consumers which need further study.