Fig. 7

Schematic of intercellular signaling in the somites. Expression of jag2b is initiated at 11 hpf in the somites, and Jag2b protein activate Notch signaling in adjacent somitic cells (∼13 hpf). Notch-activated cells then express efna1b (∼13 hpf ), and Ephrin A1b protein transduces signals to adjacent somitic cells to drive wnt16 expression (∼14 hpf ). Wnt16 regulates dlc and dld expression in the ventral domain of the somite (sclerotome), where angioblasts receive Dlc/Dld signaling to become hemogenic endothelial cells (∼16 hpf ). Hemogenic endothelial cells express gata2b (∼18 hpf ) and arise in the ventral floor of the DA (∼23 hpf ). The cross-hatched region within the somite denotes the adaxial domain where jag2b-expressing slow muscle precursors are located. Colors of cells relate to the protein signal scheme above. nc, notochord; nt, neural tube.