Fig. 1. Chondrogenic neural crest cells do not form pharyngeal cartilage elements in endoderm mutants. (A,C) (ventral views) Cartilages from 4-day-old embryos were stained with Alcian Blue, revealing the viscerocranium (green labels) and the neurocranium (red labels). Pharyngeal arch cartilages and trabeculae (arrowhead) are absent (B) or reduced (C) in cas and bon. (D,E) Transverse sections as indicated by dashed lines in A and B. Stars indicate the heart/hemicardia and arrowheads indicate arch cartilages. (F,G) radar expression in 48 hpf embryos (lateral view). (H-O) Expression of the marker dlx2. (H-M) Dorsal views. (H,I) Formation of the three streams I, II and III of dlx2-positive neural crest cells is initially normal in cas embryos. (J,K) At 24 hpf, stream III, which is already segmented in wild type, is no longer detectable in mutants. (L,M) At 30 hpf, expression of dlx2 in cas embryos is limited to stream I. (N,O) Lateral views. At 48 hpf, expression of dlx2 in cas embryos is restricted to a thin line posterior to the eye. (P-S) At 24 hpf, expression of fkd6 (P,Q) as well as Hu (R,S) appears unaffected in cas. b, branchial arches; e, eye; ep, ethmoid plate; f, fin; h, hyoid; m, mandibular; mo, mouth; no, notochord; ov, otic vesicle; pc, parachordal; t, trabeculae.