Fig. 3

Putative Xenopus NECs are not neural crest-derived.

(a) Schematic of a stage 45 tadpole (Nieuwkoop and Faber, 1967). Dotted lines: section planes in b,f–g' (magenta, transverse) and in c,i-j',l-m' (green, oblique). (b) Serotonergic cells in gill filament epithelium (putative NECs) are first detected at stage 43 (inset shows higher-power view). (c) Similar serotonergic cells are scattered in the orobranchial epithelium from stage 41 (inset shows higher-power view). (d) Schematic (modified from Nieuwkoop and Faber, 1967) showing neural crest labelling: GFP-donors, created by injecting cyto-GFP mRNA into one cell at the two-cell stage, were grown to stages 13–17, and neural folds grafted unilaterally to wild-type hosts. For grafted embryos grown to stage 53, donors were transgenic CMV-GFP embryos. (e) At stage 22, GFP labels neural crest cells migrating towards the branchial arches. (f–g^’) At stage 43, GFP labels branchial arch cartilage and surrounding mesenchyme, but not putative NECs (arrowheads) in the orobranchial epithelium. (h–j') At stage 45, GFP-positive neural crest cells are visible in the branchial arches (whole-mount and section from different embryos). GFP labels branchial arch cartilage and mesenchyme, but not putative NECs (arrowheads) in the gill filaments. (k–m') At stage 53 (transgenic CMV-GFP donors; whole-mount and section from different embryos), GFP labels branchial arch cartilage and mesenchyme, but not putative NECs (arrowheads) in the gill filaments. 5-HT, serotonin; Bac, branchial arch cartilage; Gf, gill filament; Nt, neural tube; Obc, orobranchial cavity; Oe, olfactory epithelium. Scale-bar: 50 μm.