OCT4 Regulates WNT/β‐catenin Signaling and Prevents Mesoendoderm Differentiation by Repressing EOMES in Porcine Pluripotent Stem Cells

The regulatory network between signaling pathways and transcription factors (TFs) is crucial for the maintenance of pluripotent stem cells. However, little is known about how the key TF OCT4 coordinates signaling pathways to regulate self-renewal and lineage differentiation of porcine pluripotent stem cells (pPSCs). Here, we explored the function of OCT4 in pPSCs by transcriptome and chromatin accessibility analysis. The TFs motif enrichment analysis revealed that, following OCT4 knockdown, the regions of increased chromatin accessibility were enriched with EOMES, GATA6, and FOXA1, indicating that pPSCs differentiated toward the mesoendoderm (ME) lineage. Besides, pPSCs rapidly differentiated into ME when the WNT/beta-catenin inhibitor XAV939 was removed. However, the ME differentiation of pPSCs caused by OCT4 knockdown did not rely on the activation of WNT/beta-catenin signaling because the target gene of WNT/beta-catenin signaling, AXIN2 was not upregulated after OCT4 knockdown, despite significant upregulation of WLS and some WNT ligands. Importantly, OCT4 is directly bound to the promoter and enhancers of EOMES and repressed its transcription. Overexpression of EOMES was sufficient to induce ME differentiation in the presence of XAV939. These results demonstrate that OCT4 can regulate WNT/beta-catenin signaling and prevent ME differentiation of pPSCs by repressing EOMES transcription.