Abstract

Oocyte maturation is a critical process for successful fertilization and early embryonic development. In this study, we investigated the molecular mechanisms underlying oocyte maturation in dogs by analyzing the transcriptomic profiles of miRNAs and mRNAs in canine cumulus cells (CCs) and oocytes during in vitro maturation (IVM). RNA sequencing identified 285 miRNAs expressed in oocytes and 310 in CCs, with 282 miRNAs shared between the two cell types, highlighting the role of intercellular communication in maintaining miRNA expression equilibrium. Differential expression analysis revealed 222 mRNAs with significant differences between CCs and oocytes, including genes involved in transcriptional regulation and nuclear structure. Enrichment analyses identified pathways such as actin cytoskeleton regulation, mTOR signaling, cAMP signaling, and calcium signaling, all critical to oocyte maturation. Network analysis revealed 643 significant miRNA-mRNA coexpression relationships, suggesting miRNAs play pivotal roles in regulating mRNA expression during oocyte maturation. Notably, key miRNAs such as miR-30b, miR-375, and miR-503 were implicated in regulating genes involved in oocyte maturation pathways, while others like miR-378 and miR-21 aligned with known roles in suppressing cumulus expansion and influencing maturation. The absence of differential miRNA expression between CCs and oocytes suggests the miRNA transfer through gap junctions. These findings provide new insights into the transcriptional and post-transcriptional regulation of oocyte maturation in dogs, offering valuable knowledge to improve reproductive biotechnologies such as in vitro fertilization and embryo development in this species.