title: Regionalisation of early head ectoderm is regulated by endoderm and prepatterns the orofacial epithelium.
abstract: The oral epithelium becomes regionalised proximodistally early in development, and this is reflected by the spatial expression of signalling molecules such as Fgf8 and Bmp4. This regionalisation is responsible for regulating the spatial expression of genes in the underlying mesenchyme. These genes are required for the spatial patterning of bone, cartilage orofacial development and, in mammals, teeth. The mechanism and timing of this important regionalisation during head epithelium development are not known. Using lipophilic dyes to fate map the oral epithelium in chick embryos, we show that the cells that will occupy the epithelium of the distal and the proximal mandible primordium already occupy different spatial locations in the developing head ectoderm prior to the formation of the first pharyngeal arch and neural crest migration. Moreover, the ectoderm cells fated to become proximal oral epithelium express Fgf8 and this expression requires the presence of endoderm. Thus, the first fundamental patterning process in jaw morphogenesis is controlled by the early separation of specific areas of ectoderm that are regulated by ectoderm-endoderm interactions, and does not involve neural crest cells.
authors.affiliation: Department of Craniofacial Development, Dental Institute, Kings College London, Floor 28, Guys Hospital, London Bridge, London SE1 9RT, UK.
authors.forename: Kim E
authors.initials: KE
authors.lastname: Haworth
authors.forename: Christopher
authors.initials: C
authors.lastname: Healy
authors.forename: Pamela
authors.initials: P
authors.lastname: Morgan
authors.forename: Paul T
authors.initials: PT
authors.lastname: Sharpe
mesh_terms: D000818:Animals; D019521:Body Patterning; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism; D001934:Branchial Region / Q000196:embryology* / Q000378:metabolism; D002642:Chick Embryo; D004475:Ectoderm / Q000166:cytology* / Q000378:metabolism; D004707:Endoderm / Q000166:cytology* / Q000378:metabolism; D004848:Epithelium / Q000196:embryology / Q000378:metabolism; D005147:Facial Bones / Q000196:embryology / Q000378:metabolism; D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006257:Head; D009055:Mouth / Q000196:embryology / Q000378:metabolism; D009432:Neural Crest / Q000196:embryology / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors