Profiling And Functional Analysis Of Key MiRNAs During The Luteal Phase To Follicular Phase In Yorkshire Pig Ovary

In order to explore the regulation of miRNAs in pig ovary dynamic changes and estrus cycle,and to detecte some important miRNAs that can be used in subsequent studies to improve sow fertility,we used high-throughput sequencing methods in Yorkshire sows ovaries.The miRNA expression profiles and their differential expression patterns were detected in follicular phase(FP)and luteal phase(LP)of porcine ovary.The potential candidate miRNAs were predicted,and GO enrichment analysis and KEGG pathway analysis were performed on miRNA target genes.The selection of an important candidate miR-214 preliminary explored its expression in pig ovaries and granulosa cells during the estrus cycle.The main findings are as follows:⑴ High-throughput sequencing of ovarian small RNA libraries in Yorkshire sows during follicular and luteal phase was performed.A total of 10-12 million raw sequences were obtained in the follicular phase group and 13-16 million original sequences were obtained in the luteinizing phase group.After quality treatment,9-10 million clean reads were obtained in the FP group,and 10-13 million clean reads were obtained in the LP group,accounting for 77-93% and 75-84% of the raw sequences,respectively;⑵ Through data analysis,a total of 801 miRNAs were detected in the two libraries,among which 629 miRNAs were co-expressed in the two groups,73 miRNAs were specifically expressed in the LP group,and 99 miRNAs were specifically expressed in the FP group.A total of 112 differentially expressed miRNAs(P < 0.05)were identified by differential analysis,of which 25 miRNAs were up-regulated and 87 miRNAs were down-regulated in the LP group.⑶ The target genes of 112 differential miRNAs were predicted and 2,444 target genes were obtained.GO enrichment and KEGG pathway analysis revealed 425 differential GO terms and 60 differential pathways.Eight KEGG pathways(PI3K-Akt signaling pathway,Steroid biosynthesis,Apoptosis,Cell cycle,MAPK signaling pathway,cAMP signaling pathway,Hippo signaling pathway and mTOR signaling pathway)are closely related to the growth and development of follicles and the formation and degeneration of corpus luteum.⑷ miR-214 had the lowest expression on the 7th day and the highest expression on the14 th day in the ovary of the estrous cycle.On day 3 and day 7 of the estrous cycle,miR-214 expression levels in granulosa cells of secondary follicles were greater than those in granulosa cells of dominant follicles.and on the 7th day,the expression of miR-214 was significantly greater(P < 0.05)in SF granulosa cells than in DF granulosa cells.⑸ Through bioinformatics analysis,we screened miR-214,miR-125 b,miR-17-3p,miR-221-5p,and miR-149 as important candidate miRNAs that affect the ovarian luteal phase to follicular phase transition.