Identification and molecular characterization of genes modulating progression of an oocyte from M-I to M-II in rat ovary

Background: To achieve oocyte competence for successful fertilization, bidirectional communication between oocyte and granulosa cells is crucial. The acquisition of meiotic competency in oocyte is facilitated by various regulatory genes however, expression pattern of these genes is not well documented during meiotic transition from Metaphase-I to Metaphase-II stage. Therefore, the present research analyzed the expression pattern of regulatory genes that are involved in the transition from M-I to M-II stages in rat oocyte.

Methods: The analysis of the data was conducted by applying an array of bioinformatic tools. The investigation of gene group interactions was carried out by employing the STRING database, which relies on co-expression information. The gene ontology (GO) analysis was performed utilizing the comparative GO database. Functional annotation for GO and pathway enrichment analysis were performed for genes involved in networking. The GO obtained through computational simulations was subsequently validated using quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis.

Results: The findings of our study suggest that there is a distinct gene expression pattern in both the oocyte and granulosa cells. This pattern indicates that oocyte-secreted factors, such as BMP15 and GDF9, play a crucial role in regulating the progression of the meiotic cell cycle from the M-I to M-II stages. We have also examined the level of mRNA expression of genes including CYP11A1, CYP19A1, and STAR, which are crucial for the steroidogenesis.

Conclusions: It is fascinating to observe that the oscillatory pattern of specific key genes may hold significance in the process of in vitro oocyte maturation, specifically during the transition from the M-I to M-II stage. It might be useful for determining biomarker genes and potential pathways that play a role in attaining oocyte competency, thereby aiding in the assessment of oocyte quality for the purpose of achieving successful fertilization.