| |
Fig. 6. Neural crest derivatives fail to differentiate in Id3-injected embryos. (A) Forced Id3 expression leads to the formation of substantially fewer melanocytes on the injected side (arrowhead) of embryos that were injected in one cell at the two-cell stage. (B,C) Embryos injected bilaterally with Id3 mRNA (C) show more dramatic deficits in melanocyte formation (arrows) and also have reduced or absent dorsal fins as compared to sibling control embryos (B). (D) Following forced expression of Id3, neural crest cells that populate the branchial arches fail to give rise to chondrocytes, as visualized by Sox9 expression (black arrows) on the injected (D) versus control (E) side of the embryo. Expression of Sox9 in the developing ear (red arrows) is unperturbed by Id3 expression. (F) The differentiation of N-tubulin-expressing primary neurons is also inhibited on the Id3-injected side of the embryo (arrowhead). (G) Rohon-Beard sensory neurons, as marked by expression of brn3, are particularly sensitive to Id3 (injected side marked by arrowhead and β-gal staining, blue). (H) The effects of Id3 in these experiments are directly on the ectoderm. In situ hybridization for muscle actin expression shows that the underlying mesoderm is unperturbed on the injected side of the embryo. |
