Jag1b-Notch2 signaling regulates DV patterning of the zebrafish facial skeleton. (A,B) Skeletal staining at 5 dpf showing cartilage (blue) and bone (red). jag1bb1105 mutants display a characteristic kink (arrow) behind the eye, which is not seen in the wild type (Wt). (C) Schematic of Jag1b protein showing DSL (blue), EGF-like (white), cysteine-rich (red), transmembrane (TM) and intracellular (yellow) domains. The jag1bb1105 lesion is a nonsense mutation (W223*) that truncates Jag1b in the DSL domain required for Notch binding. (D-G) Dissected facial skeletons from wild-type (D), jag1bb1105 (E), notch2-MO (F) and 20-28 hpf heat shock-treated hsp70I:Gal4; UAS:JAG1 (G) larvae. Schematics (below) show ventral (red) and dorsal (green) elements derived from the mandibular and hyoid arches, with bones more lightly shaded. The maxillary-derived pterygoid process (Ptp) is in gray. Scale bar: 100 µm. (H) Calcein Green bone staining at 5 dpf shows Op-to-Br transformations in jag1bb1105 and notch2-MO larvae and Br-to-Op transformations in 20-28 hpf heat shock-treated hsp70I:Gal4; UAS:JAG1 larvae. (I) The proportion of wild-type, jag1bb1105, jag1b-MO, notch2-MO and 20-28 hpf heat shock-treated hsp70I:Gal4; UAS:JAG1 larvae showing normal (yellow), reduced (red) or transformed (blue) skeletal elements. M, Meckel′s; Pq, palatoquadrate; Hm, hyomandibular; Sy, symplectic; Ch, ceratohyal; Op, opercle bone; Br, branchiostegal ray bone. The proportion of larvae exhibiting ectopic cartilage (blue) is also shown.