Expression of jag1b, notch2 and hey1 is regulated by Jagged-Notch and Edn1 signaling. (A-N) Confocal sections of double-fluorescence in situ hybridizations showing mandibular (m) and hyoid (h) arch expression of jag1b (green) and notch2 (red) (A-G) and of dlx2a (green) and hey1 (red) (H-N). In wild types, jag1b and hey1 CNCC expression expands ventrally from 28 hpf (A,H) to 32 hpf (B,I) and 36 hpf (C,J). In jag1bb1105 (D,K) and notch2-MO (E,L) zebrafish embryos, jag1b and hey1 expression is reduced and strong ventral notch2 expression (brackets) is expanded at 36 hpf. Arrowheads in J,K indicate ventral mesoderm expression of hey1, which is unaffected in jag1bb1105 mutants. In 20-28 hpf heat shock-treated hsp70I:Gal4; UAS:JAG1 (F,M) and edn1-/- (G,N) embryos, jag1b and hey1 expression is expanded into ventral CNCCs (arrows) and notch2 expression is reduced at 36 hpf. Endodermal pouches are outlined in A-G.