Differential expression and functional analysis of circular RNA in ovaries of Tibetan sheep with different fecundity

This study represents one of the first investigations of circular RNAs (circRNAs) in the ovaries of Tibetan sheep, with a focus on their potential role in reproductive performance. The aim was to identify circRNAs involved in ovarian development and fertility regulation. High-throughput sequencing was applied to analyze ovarian tissue samples from 20 Tibetan sheep, leading to the identification of 82 differentially expressed circRNAs between the single multiparous (SL) and multiple multiparous (ML) groups, with 35 upregulated and 47 downregulated circRNAs. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses revealed significant associations with pathways involved in cell growth, cell cycle progression, energy metabolism, hormone regulation, and cellular transport. Protein-protein interaction (PPI) analysis identified key target genes, including EP300, CUL1, and oar-miR-654-5p. A comprehensive quaternary regulatory network, integrating circRNA, miRNA, mRNA, and related pathways, was constructed. This study provides novel insights into the molecular mechanisms underlying fertility in Tibetan sheep and identifies potential molecular targets for improving reproductive biotechnology. These findings lay the foundation for future molecular breeding programs aimed at enhancing fertility in Tibetan sheep.