Fig. 2. Fate of chondrogenic neural crest cells in wild-type and cas embryos. (A,B) Dorsal view of the head of live 24 hpf embryos. Note in cas an additional lobular structure (arrowhead). (C,D) Dorsal neuroectoderm and neural crests posterior to the otic vesicle were labelled by activation of DMNB-caged fluorescein (see Materials and Methods). By 28 hpf, neural crest stream III (white arrowheads) has initiated segmentation in wild-type but not in cas embryos (D). (E-H). Same as in C,D but DMNB-caged fluorescein was activated in precursors of streams II (black arrowhead) and III. Embryos were fixed at 28 hpf and processed for detection of fluorescein (E-H, orange) and dlx2 (G,H, purple). (E-H) Streams I, II and III are present but dlx2 expression is downregulated in stream III in cas embryos (H). (I-L) Dorsal views. hoxb2 (I,J) and hoxb3 (K,L) expressions at 28 hpf reveal the correct AP value of stream II and III, which adopt an ectopic lateral position in cas embryos. (M,N) Lateral view. 30 hpf embryos were labelled with Acridine Orange, revealing increased cell death in the region of the three cranial neural crest streams in cas embryos. (O-Q) These results were confirmed by TUNEL analysis and sectioning (Q). e, eye; ov, otic vesicle.