Dishevelled 2 coordinates aortic Notch signaling through primitive myeloid and hemogenic endothelial cells during hematopoietic stem cell specification
Hematopoietic stem cells (HSCs) arise from the hemogenic endothelium in the dorsal aorta through the endothelial-to-hematopoietic transition, a tightly regulated developmental process requiring coordinated signaling from the developing hematopoietic niche. Wnt and Notch signaling are essential for HSC specification, with Wnt functioning upstream of Notch; however, the molecular mechanisms by which these pathways are coordinated during HSC development remain poorly understood. Here, we identify Disheveled 2 (Dvl2), a key intracellular Wnt scaffold protein, as an essential regulator of HSC identity specification in zebrafish. Loss of dvl2 impaired HSC specification and reduced Notch signaling in the dorsal aorta, despite normal canonical Wnt activity in the developing endothelium, suggesting that Dvl2 regulates HSC specification independently of endothelial beta-catenin signaling. Hemogenic endothelial-specific expression of the Notch intracellular domain rescued HSC defects in dvl2 morphants, demonstrating that Dvl2 functions upstream of Notch activation in the hemogenic endothelium during HSC specification. In addition, loss of dvl2 reduced primitive macrophages and neutrophil populations. Restoration of primitive myeloid cells through gata1a knockdown rescued both endothelial Notch signaling and HSC defects, demonstrating that Dvl2 is also required for the supportive immune cells that induce HSC identity. Together, these findings reveal that Dvl2 coordinates hemogenic endothelial and immune niche cues to control HSC identity specification.