Stage-specific remodeling of wingless-related integration sites (WNT) signaling during oocyte-to-embryo transition in pigs.

Abstract

The WNT signaling pathway is a central regulator of cell polarity, adhesion, cytoskeletal dynamics, and lineage specification during early embryonic development. Although its roles have been extensively studied in murine and human models, the temporal regulation and pathway architecture of WNT signaling during early porcine development remain poorly defined. Here, we performed a comprehensive transcriptomic analysis to characterize WNT pathway dynamics across key stages of pig in vitro development, including immature oocytes (IMO), mature oocytes (MO), zygotes (ZY), cleaved embryos (2-4 cells; CL), and blastocysts (BL). Global analyses revealed major transcriptomic transitions (FDR <0.05; |Fold Change| ≥2) during oocyte maturation and blastocyst formation, whereas zygotes and cleaved embryos exhibited highly similar expression profiles. Module-based and gene-level analyses showed that oocyte maturation is associated with increased expression of extracellular WNT antagonists and components of the β-catenin destruction complex, together with selective regulation of Frizzled receptors, consistent with tight control of canonical WNT signaling at the MII stage. Following fertilization, this inhibitory configuration was partially relieved, alongside transient upregulation of specific WNT ligands, transcriptional mediators, and adhesion-related components during zygotic genome activation and early cleavage. At the blastocyst stage, WNT signaling became increasingly associated with planar cell polarity and epithelial organization modules. Together, the data reveal a highly dynamic and stage-specific restructuring of WNT signaling during early porcine development. Our findings indicate that precise temporal modulation-rather than uniform activation-of WNT pathway components accompanies the porcine oocyte-to-embryo transition, providing a molecular framework to better understand early developmental regulation and offering insights relevant to reproductive biotechnology and developmental biology.

Early development depends on precise communication between cells, guided by molecular signaling pathways. One of these pathways, known as WNT signaling, plays a key role in shaping cells, controlling their interactions, and guiding early embryonic organization. While WNT signaling has been well studied in some model species, much less is known about how it operates during early development in pigs. In this study, we analyzed how genes involved in WNT signaling change their activity during key stages of porcine development, from immature and mature egg cells (oocytes) through fertilized eggs (zygotes) to the blastocyst stage. Using RNA sequencing, we found that WNT-related genes regulated in a stage-specific manner. Our results show that WNT signaling is strongly restrained as the egg cell completes maturation, likely to prevent inappropriate gene activation before fertilization. Then, this restraint is partially lifted, allowing the early embryo to re-engage WNT signaling as it begins to activate its own genome. At later stages, WNT signaling becomes increasingly linked to cell structure and tissue organization during blastocyst formation. These findings provide new insight into how early porcine development is regulated at the molecular level and help explain why timing of signaling pathways is essential for successful embryo development.