From Methylation to Pluripotency: Epigenetic Programming in Early Embryo Development

Objective: Early embryonic development is orchestrated by transcriptional and epigenetic mechanisms that regulate pluripotency and differentiation. This study aimed to investigate the stage-specific expression of key transcription factors (Oct-3/-4, Sox-2, Nanog, SSEA-1, and c-Myc) and DNA methylation enzymes (Dnmt1 and Dnmt3) during the pre-implantation period in a rat model. Materials and Methods: Embryos were collected at the 2-8 cell, 8-16 cell, and blastocyst stages. Gene expression levels were assessed using real-time PCR, while protein localisation was evaluated via immunofluorescence staining. Results: Oct-3/-4 and Sox-2 exhibited the highest levels of expression at the 2–8 cell stage, which suggests that they play an important role in the maintenance of pluripotency at an early stage. Nanog, c-Myc, and Dnmt3 were significantly upregulated at the blastocyst stage, indicating their involvement in lineage commitment. Dnmt-1 was consistently expressed across all stages, which supports its role in epigenetic memory. Discrepancies between SSEA-1 gene expression and protein detection suggested post-transcriptional regulation. Conclusion: These findings emphasise the dynamic and coordinated functions of transcriptional and epigenetic regulators during the early stages of embryogenesis. Combined mRNA and protein analysis provides a comprehensive molecular profile that is relevant to reproductive medicine and developmental biology.