Fig. 4

Early exposure to constitutively active (ca)Alk3 inhibits neural crest (NC) traits and stimulates premature transcription of Hairy1. a, b Transverse sections of control GFP (a) showing labeled cells that colonized the dorsal root ganglion (DRG) primordium as well as ectoderm (arrows). In contrast, no significant NC cell emigration is evident in caAlk3-GFP transfected neural tubes (NTs) (b). The NC marker HNK1 is in red. c, d Transverse sections following an extended 2-h pulse with BrdU. Embryos were sacrificed 16 h after a dorsally directed electroporation of either control GFP (c–c”) or caAlk3 (d–d”). Arrowheads point to GFP+/BrdU+ cells. Arrows point to GFP+/BrdU− cells. e Quantification of the mean percentages ± standard error of the mean of BrdU+/GFP+ cells of total GFP+ cells in the dorsal NT (about 10 nuclei were counted per hemi-NT; *P < 0.005). f–i’ caAlk3 downregulates Foxd3 mRNA (g, g’, arrow) and prematurely upregulates Hairy1 to a level similar to that apparent in the floor plate (FP; i, i’, arrow) when compared to the corresponding contralateral sides or to control GFP-electroporated NTs that show a similar level of bilateral transcript expression (f, f’, h, h’). Bar for a, b = 50 μM; c, d = 40 μM; c’, c” d’, d” = 30 μM; f–i’ = 40 μM