title: Waking-up the sleeping beauty: recovery of the ancestral bird odontogenic program.
abstract: Recent advances in molecular and developmental genetics have provided tools for understanding evolutionary changes in the nature of the epithelial-mesenchymal interactions regulating the patterned outgrowth of the tooth primordia. Tissue recombination experiments in mice have identified the oral epithelium as providing the instructive information for the initiation of tooth development. Teeth were lost in birds for more than 80 million years ago, but despite their disappearance, a number of gene products and the requisite tissue interactions needed for tooth formation are found in the avian oral region. It is believed that the avian ectomesenchyme has lost the odontogenic capacity, whilst the oral epithelium retains the molecular signaling required to induce odontogenesis. In order to investigate the odontogenic capacity of the neural crest-derived mesenchyme and its potential activation of the avian oral epithelium, we have realized mouse neural tube transplantations to chick embryos to replace the neural crest cells of chick with those of mouse. Teeth are formed in the mouse/chick chimeras, indicating that timing is critical for the acquisition of the odontogenic potential by the epithelium and, furthermore, suggesting that odontogenesis is initially directed by species-specific mesenchymal signals interplaying with common epithelial signals.
authors.affiliation: Department of Craniofacial Development, King's College London, Dental Institute, London Bridge, London SE1 9RT, UK. thimios.mitsiadis@kcl.ac.uk
authors.forename: Thimios A
authors.initials: TA
authors.lastname: Mitsiadis
authors.forename: Javier
authors.initials: J
authors.lastname: Caton
authors.forename: Martyn
authors.initials: M
authors.lastname: Cobourne
mesh_terms: D000818:Animals; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000096:biosynthesis; D001921:Brain / Q000502:physiology; D002642:Chick Embryo / Q000502:physiology*; D002678:Chimera / Q000254:growth & development / Q000502:physiology*; D004848:Epithelium / Q000502:physiology; D051524:Fibroblast Growth Factor 8 / Q000096:biosynthesis; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D053823:Hedgehog Proteins / Q000096:biosynthesis; D018398:Homeodomain Proteins / Q000096:biosynthesis; D017403:In Situ Hybridization / Q000662:veterinary; D051957:MSX1 Transcription Factor / Q000096:biosynthesis; D008648:Mesoderm / Q000502:physiology*; D051379:Mice; D009432:Neural Crest / Q000502:physiology; D009805:Odontogenesis / Q000235:genetics / Q000502:physiology*; D014157:Transcription Factors / Q000096:biosynthesis; D000097577:Homeobox Protein PITX2
chemical_list: D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D051524:Fibroblast Growth Factor 8; D053823:Hedgehog Proteins; D018398:Homeodomain Proteins; D051957:MSX1 Transcription Factor; D014157:Transcription Factors; D000097577:Homeobox Protein PITX2; C525810:Bmp4 protein, mouse; C496456:FGF8 protein, human; C484084:Msx1 protein, mouse