Fig. 9. Transplants suggest that lsn^w24 functions cell autonomously in the endoderm and endoderm is required for ENS development. (A-D) Transplantation of wild-type endodermal cells partially rescues posterior arch cartilage formation in lsn mutants. (A) At blastula stage, fluorescein-dextran labelled wild-type cells expressing Tar^* were transplanted into host and allowed to develop. The lateral view of the head region at 72 hpf shows grafted cells (green) have differentiated into pharyngeal endoderm derivatives. (B-D) Ventral views of 5 dpf larvae stained with Alcian Blue to show cartilages. (B) Wild-type control. All lower jaw cartilages are clearly identifiable. (C) lsn mutant larvae transplanted with wild-type cells showing rescue of posterior ceratobranchial (3-5) in the vicinity of transplanted Tar^*-expressing wild type cells (black staining) in the pharyngeal arch endoderm (arrowheads). (D) lsn mutant that lacks posterior ceratobranchials. (E-H) Casanova morphant embryos have no intestinal endoderm and no migrating ENS precursors. Dorsal views of 48 hpf control embryos (E,F) and cas morphant embryos (G,H) hybridized with riboprobes for phox2b (E,G) or foxa3 (F,H) showing a complete lack of phox2b-expressing cells in the region of the intestine of morphant embryos (G) that also completely lack intestinal endoderm (H). Arrowheads in E indicate migrating ENS precursors. m, Meckel's cartilage of the mandibular arch; ch, ceratohyal cartilage; 1-5 ceratobranchial cartilages; G, intestine; L, liver, P, pancreas.