WDR5 and Myc Cooperate to Regulate Formation of Neural Crest Stem Cells

WDR5 is a multifunctional scaffolding protein with established roles in chromatin regulation and pluripotency, but its functions in early vertebrate development remain poorly understood. Here, we show that Xenopus wdr5 is expressed in blastula stem cells and enriched in neural crest cells during neurulation. Morpholino-mediated depletion of wdr5 abolished neural crest marker expression both in embryos and in reprogrammed explants while unexpectedly expanding neural plate border and neural plate domains. Gain-of-function experiments revealed a striking dose-dependent effect: low levels of wdr5 enhanced neural crest formation, whereas high levels suppressed it, suggesting a requirement for precise stoichiometry with interacting partners. We identify myc as a critical cofactor for wdr5 in neural crest specification--wdr5 and myc physically interact in early embryos, and co-expression at defined ratios rescues neural crest formation while either, individually, is inhibitory. Domain-specific mutagenesis showed that the WBM site of wdr5 is required for myc-dependent activation of neural crest genes, while the WIN site regulates myc expression itself; both domains are necessary to rescue wdr5 loss-of-function phenotypes. Moreover, modulation of myc levels phenocopied wdr5s dose-sensitive effects, reinforcing the importance of balanced wdr5-myc activity. These findings reveal that wdr5 orchestrates neural crest development through multiple, domain-specific mechanisms--integrating stoichiometric control with partner-specific transcriptional regulation--and highlight parallels with Wdr5-Myc cooperation in cancer, underscoring the broader relevance of precise cofactor ratios in cell fate decisions.