title: The dissociation of the Fgf-feedback loop controls the limbless state of the neck.
abstract: In tetrapods, limbs develop at two specific positions along the anteroposterior axis of the embryo, whereas other regions of the embryo, most prominently the neck and the flank, are limbless. However, the flank can generate an ectopic limb when the Fgf-feedback loop crucial for the initiation of limb budding is activated. Thus, despite its limblessness, the flank is a limb-competent area. Using the chick embryo as model, we investigated whether the neck, as the flank, has the competence to form a limb, and what mechanism may regulate its limblessness. We show that forelimb lateral mesoderm plus ectoderm grafted into the neck can continue limb development, suggesting that the neck does not actively inhibit this process. However, neck tissues themselves do not support or take part in limb formation. Hence, the neck is limb-incompetent. This is due to the dismantling of Fgf signalling at distinct points of the MAPK signalling cascade in the neck lateral mesoderm and ectoderm.
authors.affiliation: Department of Craniofacial Development, King's College London, Floor 27, Guy's Tower, Guy's Hospital, London Bridge, London SE1 9RT, UK.
authors.forename: Corinne
authors.initials: C
authors.lastname: Lours
authors.forename: Susanne
authors.initials: S
authors.lastname: Dietrich
mesh_terms: D000818:Animals; D002642:Chick Embryo; D004475:Ectoderm / Q000502:physiology / Q000637:transplantation; D005121:Extremities / Q000196:embryology; D025461:Feedback, Physiological; D051526:Fibroblast Growth Factor 10 / Q000502:physiology; D051524:Fibroblast Growth Factor 8 / Q000502:physiology; D005346:Fibroblast Growth Factors / Q000502:physiology*; D020935:MAP Kinase Signaling System / Q000502:physiology; D008648:Mesoderm / Q000378:metabolism / Q000637:transplantation; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009333:Neck / Q000196:embryology*; D010766:Phosphorylation; D051497:Receptor, Fibroblast Growth Factor, Type 2 / Q000096:biosynthesis; D015398:Signal Transduction
chemical_list: D051526:Fibroblast Growth Factor 10; D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors; D051497:Receptor, Fibroblast Growth Factor, Type 2; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3