RNA Sequencing Reveals the Involvement of Serum Exosomal miRNAs in Early Pregnancy in Cattle

Simple Summary Low fertility is the main cause of low productivity in beef cattle, and the non-conception of cows after fertilization is an important factor contributing to this phenomenon. miRNAs may exert unique metabolic and immune effects on the early gestation process in cattle. In this study, serum exosomes on the 0 th, 14 th, and 21 st days of the early gestation of cattle were obtained by simultaneous estrus technology, and the expression profile of exosomal miRNA was detected by RNA-seq technology. Among them, bta-miR-3604, bta-miR-2889, bta-miR-3432a, and bta-miR-409b are newly discovered miRNAs. This study can provide a theoretical reference for the screening of early pregnancy establishment and maternal pregnancy recognition (MRP) molecular markers in cattle.Abstract Low fertility is the main cause of the low productivity in beef cattle and is mainly associated with a lack of conception after fertilization. The establishment of early pregnancy in cattle is a complex physiological process, and embryo implantation is crucial for the successful establishment of pregnancy. Exosomal miRNAs play an important role in regulating mammalian embryo implantation and development. This study used synchronous estrus technology to extract exosomes from bovine serum at 0, 14, and 21 days of early pregnancy and analyzed the expression profile of exosomal miRNAs through RNA-seq technology. We identified 472 miRNA precursor sequences and 367 mature miRNA sequences in the three sample groups, with the majority of the miRNAs having high abundance. Differentially expressed miRNAs (DEmiRNAs) were screened, and 20 DEmiRNAs were obtained. The differential expression analysis results show that compared to day 0, there were 15 DEmiRNAs in the serum on day 14 and 5 on day 21 of pregnancy. Compared to the 14th day of pregnancy, there were eight DEmiRNAs in the serum on the 21st day of pregnancy. Bioinformatics analysis shows that the target genes of DEmiRNAs regulated the signaling pathways closely related to early pregnancy, including the VEGF, NF-kappa B, and MAPK signaling pathways. In addition, the newly discovered miRNAs were bta-miR-3604, bta-miR-2889, bta-miR-3432a, and bta-miR-409b. These results provide a theoretical reference for screening the molecular markers for early pregnancy establishment and maternal recognition of pregnancy (MRP) in cattle and new ideas for shortening the calving interval in cows.