title: FGF/MAPK signaling is required in the gastrula epiblast for avian neural crest induction.
abstract: Neural crest induction involves the combinatorial inputs of the FGF, BMP and Wnt signaling pathways. Recently, a two-step model has emerged where BMP attenuation and Wnt activation induces the neural crest during gastrulation, whereas activation of both pathways maintains the population during neurulation. FGF is proposed to act indirectly during the inductive phase by activating Wnt ligand expression in the mesoderm. Here, we use the chick model to investigate the role of FGF signaling in the amniote neural crest for the first time and uncover a novel requirement for FGF/MAPK signaling. Contrary to current models, we demonstrate that FGF is required within the prospective neural crest epiblast during gastrulation and is unlikely to operate through mesodermal tissues. Additionally, we show that FGF/MAPK activity in the prospective neural plate prevents the ectopic expression of lateral ectoderm markers, independently of its role in neural specification. We then investigate the temporal participation of BMP/Smad signaling and suggest a later involvement in neural plate border development, likely due to widespread FGF/MAPK activity in the gastrula epiblast. Our results identify an early requirement for FGF/MAPK signaling in amniote neural crest induction and suggest an intriguing role for FGF-mediated Smad inhibition in ectodermal development.
authors: Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103, USA.
authors: Timothy J
authors: TJ
authors: Stuhlmiller
authors: Martín I
authors: MI
authors: García-Castro
mesh_terms: D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000378:metabolism; D002642:Chick Embryo; D004475:Ectoderm / Q000196:embryology; D018274:Electroporation; D005346:Fibroblast Growth Factors / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D005775:Gastrula / Q000196:embryology*; D005855:Germ Layers / Q000196:embryology* / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D017403:In Situ Hybridization; D008648:Mesoderm / Q000378:metabolism; D008853:Microscopy; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008954:Models, Biological; D009432:Neural Crest / Q000196:embryology*; D011758:Pyrroles; D051496:Receptor, Fibroblast Growth Factor, Type 1 / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D051785:Smad Proteins / Q000378:metabolism
chemical_list: D019485:Bone Morphogenetic Proteins; D011758:Pyrroles; C105686:SU 5402; D051785:Smad Proteins; D005346:Fibroblast Growth Factors; D051496:Receptor, Fibroblast Growth Factor, Type 1; D020928:Mitogen-Activated Protein Kinases