04-P007 A simplified gene regulatory network for mesendoderm formation is revealed by knockdown of single Nodal and Mix genes in axolotl embryos

ences between placodes and neural crest (induction during different times of development; different developmental potential; regulation of differentiation and migration by largely nonoverlapping sets of transcription factors) this suggests that cranial placodes and neural crest cells have an independent developmental origin from non-neural and neural ectoderm, respectively. We currently perform gain and loss of function experiments in Xenopus to test whether Dlx3, Dlx5, GATA2 and/ or GATA3 genes, which are expressed throughout the non-neural ectoderm but are absent from neural ectoderm, are involved in mediating the competence of non-neural ectoderm to respond to placode inducers.