Identification and profiling of microRNAs in the ovaries of polytocous and monotocous goats during estrus

MicroRNAs (miRNAs) play critical roles in almost all ovarian biological processes, including folliculogenesis, ovulation, luteal development, and regression. The study identified known and novel miRNAs in the ovaries of polytocous and monotocous goats by combining Solexa sequencing with bioinformatics. In total, 862 known and 53 novel miRNAs were identified in the ovaries of polytocous and monotocous goats. A total of 771 miRNAs were co-expressed in both libraries. One hundred twenty miRNAs in the ovaries of polytocous goats and 24 miRNAs in the ovaries of monotocous goats were specifically expressed. In addition, 445 miRNAs were differentially expressed in the ovaries of polytocous and monotocous goats, of which 348 were upregulated, and 97 were downregulated in the ovaries of polytocous goats compared with the ovaries of monotocous goats (P values < 0.05 and |log2 (fold change)|> 1). The expression levels of 12 randomly selected miRNAs were analyzed by stem-loop real-time quantitative polymerase chain reaction, and the results demonstrated that the expression patterns were consistent with Solexa sequencing results. KEGG analysis showed that GnRH, transforming growth factor-beta, vascular endothelial growth factor, and mammalian target of rapamycin signaling pathways, oocyte meiosis and ovarian steroidogenesis participated in follicular development and ovulation. On the basis of miRNA-mRNA network analysis and luciferase reporter assays, the ggo-miR-4488-p3_1ss10CG, bta-miR-2892-p5_1ss8CG and hsa-miR-4532_L+1R-3 were closely related with prolific traits. The results will help to further understand the role of miRNAs in kidding rate regulation.