Square T , Jandzik D , Cattell M , Hansen A , Medeiros DM .

             endothelin receptor signaling pathway

	Figure 1. Expression summary of edns in P. marinus.Left lateral views in all non-prime panels. All prime lettered panels show ventral/oral views of the correspondingly lettered panel, save C’, G’, and K’ which show horizontal sections. Developmental stage68 is indicated for each specimen in the bottom right of a panel. (A–D) ednA expression in P. marinus surrounds the stomodeum and marks the pharyngeal arches. (E–H) ednC expression in P. marinus is found around the stomodeum and on the lateral sides of the head. Arrows in F point to mesenchymal ednC expression below the superficial expression in the ectoderm. (I–L) ednE expression in P. marinus is found along the somites, and throughout the facial and pharyngeal skeleton. All scale bars represent 100 μm. he, heart; meso, mesoderm; PAs, pharyngeal arches; st, stomodeum.
	Figure 2. Expression summary of ednrs in P. marinus.Left lateral views in all non-prime panels save F, which is a dorsal view with anterior to the top. All prime lettered panels show a ventral view of the correspondingly lettered panel save D’ and I’, which are horizontal sections, and G’, which is a dorsal view with anterior facing away from the page. Developmental stage68 is indicated for each specimen in the bottom right of a panel. (A–E) ednra expression in P. marinus is found in mesoderm, the heart, and the post-migratory future head skeleton. Arrow in A indicates anterior mesoderm expression of ednra. Arrowhead in A indicates ednra expression in the nascent heart. Arrows in D indicate ednra expression consistent with lateral plate mesoderm. Red line labeled D’ in D indicates the approximate plane of section in D’. Note expression in the future head skeleton (CNCCs) shown in D’. (F,G) ednrb expression in P. marinus marks migratory NCCs. Arrows in I indicate expression consistent with dorsal root ganglia. Arrowhead in I indicates expression consistent with the earliest migrating pigment cells. Red line labeled I’ in I indicates the approximate plane of section in I’. Note expression in the future head skeleton (CNCCs) shown in I’. Arrows in G’ indicate trunk NCCs still poised at the neural crest. All scale bars represent 100 μm, save the scale bar in panel D which is 500 μm. NCCs, neural crest cells; st, stomodeum.
	Figure 3. Expression summary of edns in X. laevis.Left lateral views in all non-prime panels save (A), which is an anterior view. Prime panels show anterior views of the correspondingly lettered panel. Developmental stage69 for each specimen is indicated in the bottom right corner of a panel. (A–D) edn1-b expression in X. laevis marks ectoderm around the nasal placodes, and ventral non-NCC mesenchyme and epithelia in the pharyngeal arches. (E–H) edn3-a expression in X. laevis marks ectoderm where future ednrb2-positive cells will migrate. All scale bars represent 100 μm, save those in E and G which represent 500 μm.
	Figure 4. Expression summary of ednrs in X. laevis.Left-lateral views in all non-prime panels save (A,B), which are dorsal (A) an anterior (B) views. All prime panels show anterior/oral views of the correspondingly lettered panel save K’, which is a dorsal view. Developmental stage69 for each specimen is indicated in the bottom right corner of a panel. (A–G) ednra expression in X. laevis. (A) ednra-a uniquely marks pre-migratory NCCs. (B–G) ednra-b expression in migratory and post-migratory NCC derivatives, nephrostomes, the heart, and fin mesenchyme. (H–J) ednrb1-a expression in X. laevis marks the eye and medial pharyngeal arch NCCs. (K–M) ednrb2-c expression in X. laevis marks migratory pigment cells, nerves, and the forebrain. All scale bars represent 100 μm, save those in (D,G,K’,L,M) which represent 500 μm.
	Figure 5. Lamprey ednA expression is reminiscent of gnathostome edn1 expression, despite low support for strict orthology.Oral/anterior views in (A–C’,E,F,H). Left lateral views in (C,D,G,I). Developmental stage6869 for each specimen is indicated in the bottom right corner of a panel. (A–D) X. laevis expression of edn1-b from stage 19 to 33. Dotted outline in A surrounds the cement gland. Arrows in B indicate expression in ectoderm which will eventually contribute to the nostrils (E–I) P. marinus expression of ednA from stage 22.5 to 26.5. Arrows in F indicate expression in ectoderm which will eventually move rostrally to cover the nasohypophyseal plate, contributing to the future medial nostril. In a similar sequence, both genes are expressed in bilateral patches above the future mouth, surrounding the nasal placodes/nasohypophyseal plate, in pharyngeal arch mesoderm and ectoderm, and just below the stomodeum. All scale bars represent 100 μm. cg, cement gland; nhp, nasohypophyseal plate; np nasal placode; st, stomodeum.
	Figure 6. Lamprey ednE and gnathostome edn3 expression patterns both predict neural crest-derived melanophore migration routes.All panels show left lateral views. Developmental stage6869 for each specimen is indicated in the bottom right corner of each panel. ISH panels (A-F) are labeled with the targeted gene transcript in the top right corner. Arrowheads in C and D mark regions where edn3-a (C) or ednE (D) are expressed. Arrowheads in E and F indicate cells expressing ednrb2-a (E) and ednrb (F). Panels G and H show light microscopy photos of larval X. laevis (G) and P. marinus (H). Arrowheads in (G,H) indicate areas where pigment cells migrated. All scale bars represent 100 μm.
	Fig. S6. Expression of edn1-3, ednra, and ednrb in X. laevis. Left lateral views in panels A, D, G, H, J, L, O, and R. Sections shown in panels B, C, E, F, I, K, M, N, P, Q, and S correspond to the labeled red line in the wholemount ISH panel for each gene. Developmental stage69 is indicated in the bottom right corner of the wholemount panel for each specimen. Note strong background staining with the edn2-a CDS probe in the brain (I). Arrows in O and P indicate ednrb2-a expression in the branchial nerves. Arrows in Q indicate expression consistent with dorsal root ganglia. Arrowheads in Q indicate expression in melanophores. Arrows in R and S indicate ednra-b expression in nephrostomes.
	edn1 (endothelin 1) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 19, anterior view, dorsal up.
	edn3 (endothelin-3) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 23, lateral view, anterior left, dorsal up.
	edn3 (endothelin-3) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 33, lateral view, anterior left, dorsal up.
	ednrb (endothelin receptor type B) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 35, lateral view, anterior left, dorsal up.
	ednrb2 (endothelin receptor B subtype 2) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 35, lateral view, anterior left, dorsal up.
	edn2 (endothelin 2) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 33, lateral view, anterior left, dorsal up.

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