Jag1b generally represses ventral gene expression in the pharyngeal arches. (A-U) In situ hybridizations showing the mandibular and hyoid arch expression of dlx6a (A-C), epha4b (D-F), msxe (G-I), hand2 (M-O), ednra2 (P-R) and edn1 (S-U) at 36 hpf and of bapx1 (J-L) at 40 hpf. The expression of dlx6a, epha4b, msxe and bapx1 is dorsally expanded in jag1bb1105 zebrafish embryos (B,E,H,K) and is greatly reduced in 20-28 hpf heat shock-treated hsp70I:Gal4; UAS:JAG1 embryos (C,F,I,L). hand2 expression is reduced in UAS:JAG1 embryos, whereas ednra2 and edn1 expression is unaffected in jag1bb1105 and UAS:JAG1 embryos. Endodermal pouches are outlined.