Authors:

Jennifer Fenner

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About Paper:

Wnt signaling drives germ layer (endoderm, mesoderm, and ectoderm) specification and patterning along the anterior-posterior (AP) axis during early embryonic development of across metazoans from cnidarians to humans. Despite the importance of Wnt signaling in many developmental processes we still have a limited understanding of how diverse Wnt signals are modulated during embryogenesis in any model system. In sea urchin embryos AP axis formation is controlled by an integrated Wnt signaling network of canonical (Wnt/β-catenin) and non-canonical (Wnt/JNK and Wnt/PKC) pathways. We have previously shown that several extracellular Wnt modulators (e.g., DKKs and sFRPs) regulate the AP Wnt signaling network during positioning of each early germ layer gene regulatory network (GRNs) along the AP axis. Here, we examined the role of a poorly characterized extracellular Wnt signaling modulator, Wnt inhibitory factor-1 (Wif1), during early sea urchin embryogenesis. We show that wif1 expression in the posterior endomesoderm is regulated by canonical and non-canonical Wnt signaling but that BMP2/4/7 signaling activates wif1 expression in the dorsal ectoderm. Perturbations of Wif1 result in downregulation of key genes in the endomesoderm GRN leading to gastrulation defects. Our functional assays also indicate that during late blastula stages Wif1 in the dorsal ectoderm works synergistically with Wnt7 to position specific anterior neuroectoderm (ANE) GRN components around the anterior pole. Together, our findings show that Wif1 is a previously uncharacterized member of the posterior Wnt signaling landscape that establishes critical regulatory subcircuits in the sea urchin endomesoderm GRN. And that activation of Wif1 by dorsal BMP2/4/7 signaling and Wif1's subsequent refinement of patterning within the ANE territory establishes an important link between anterior-posterior and dorsal-ventral axial patterning processes.

Source:

Auburn University / College of Sciences and Mathematics / 2025

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Co-authors:

Jennifer Fenner