| Summary: | <p>Abstract</p> <p>Background</p> <p>The maternal contribution of transcripts and proteins supplied to the zygote is crucial for the progression from a gametic to an embryonic control of preimplantation development. Here we compared the transcriptional profiles of two types of mouse MII oocytes, one which is developmentally competent (MII<sup>SN </sup>oocyte), the other that ceases development at the 2-cell stage (MII<sup>NSN </sup>oocyte), with the aim of identifying genes and gene expression networks whose misregulated expression would contribute to a reduced developmental competence.</p> <p>Results</p> <p>We report that: 1) the transcription factor Oct-4 is absent in MII<sup>NSN </sup>oocytes, accounting for 2) the down-regulation of Stella, a maternal-effect factor required for the oocyte-to-embryo transition and of which Oct-4 is a positive regulator; 3) eighteen Oct-4-regulated genes are up-regulated in MII<sup>NSN </sup>oocytes and are part of gene expression networks implicated in the activation of adverse biochemical pathways such as oxidative phosphorylation, mitochondrial dysfunction and apoptosis.</p> <p>Conclusion</p> <p>The down-regulation of Oct-4 plays a crucial function in a sequence of molecular processes that leads to the developmental arrest of MII<sup>NSN </sup>oocytes. The use of a model study in which the MII oocyte ceases development consistently at the 2-cell stage has allowed to attribute a role to the maternal Oct-4 that has never been described before. Oct-4 emerges as a key regulator of the molecular events that govern the establishment of the developmental competence of mouse oocytes.</p>
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