Wdr5 and Myc cooperate to regulate formation of neural crest stem cells.

Wdr5, a multifunctional scaffolding protein, with established roles in chromatin regulation and pluripotency, but its functions in early development remain poorly understood. Here, we show that Xenopus wdr5 is expressed in blastula stem cells and enriched in neural crest cells. Depletion of wdr5 abolished neural crest gene expression in embryos and in reprogrammed explants while expanding neural plate border and neural plate domains. Gain-of-function experiments revealed striking dose-dependent effects: low Wdr5 enhanced neural crest formation, whereas high levels suppressed it, suggesting a requirement for precise stoichiometry with interacting partners. We identify Myc as an essential co-factor for Wdr5 in neural crest - Wdr5 and Myc physically interact and co-expression at defined ratios rescues neural crest formation. We further show that the Wdr5 WBM site is required for Myc-dependent activation of neural crest genes, whereas the WIN site regulates myc expression itself; both domains are necessary to rescue wdr5 depletion. These findings reveal that Wdr5 orchestrates neural crest development through multiple, domain-specific mechanisms, integrating stoichiometric control with partner-specific transcriptional regulation, and underscores the importance of precise co-factor ratios in cell fate decisions.