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First published online June 6, 2008
doi: 10.1242/10.1242/dev.020123
Research Report |
1 Evolution des Régulations Endocriniennes, CNRS UMR 5166, Muséum
National d'Histoire Naturelle, Paris, France.
2 Service de Chirurgie Plastique, Maxillofaciale et Stomatologie, Hôpital
Necker-Enfants Malades, 149, rue de Sèvres, 75015 Paris, France.
3 Biologie du Développement, CNRS UMR 7622, Université Pierre et
Marie Curie, Paris, France.
Authors for correspondence (e-mails:
glevi{at}mnhn.fr;
gerard.couly{at}nck.ap-hopparis.fr)
Accepted 29 April 2008
SUMMARY
Morphogenesis of the facial skeleton depends on inductive interactions between cephalic neural crest cells and cephalic epithelia, including the foregut endoderm. We show that Shh expression in the most rostral zone of the endoderm, endoderm zone I (EZ-I), is necessary to induce the formation of the ventral component of the avian nasal capsule: the mesethmoid cartilage. Surgical removal of EZ-I specifically prevented mesethmoid formation, whereas grafting a supernumerary EZ-I resulted in an ectopic mesethmoid. EZ-I ablation was rescued by Shh-loaded beads, whereas inhibition of Shh signalling suppressed mesethmoid formation. This interaction between the endoderm and cephalic neural crest cells was reproduced in vitro, as evidenced by Gli1 induction. Our work bolsters the hypothesis that early endodermal regionalisation provides the blueprint for facial morphogenesis and that its disruption might cause foetal craniofacial defects, including those of the nasal region.
Key words: Sonic hedgehog, Cephalic neural crest cells, Endoderm, Foregut, Mesethmoid, Nasal capsule, Chick
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