title: Expression of chick Barx-1 and its differential regulation by FGF-8 and BMP signaling in the maxillary primordia.
abstract: The vertebrate face develops from a series of primordia surrounding the primitive mouth and is thought to be patterned by the differential expression of homeobox-containing genes. Here we describe the isolation of the chick homologue of the homeobox-containing gene, Barx-1, and show its expression in the developing facial primordia, stomach, and appendicular skeleton. In the maxillary primordia, mesenchymal expression of Barx-1 is complementary to that of Msx-1, which correlate with overlying epithelial expression of Fgf-8 and Bmp-4, respectively. We show that epithelial signals are required to maintain Barx-1 expression and that FGF-8 can substitute for the epithelium. By contrast, BMPs reduce Barx-1 expression and can antagonize FGF-8 signaling. This suggests that in vivo, FGF-8/BMP signaling may regulate Barx-1 gene expression. This provides evidence that the differential expression of FGF-8 and BMPs may determine homeobox-containing gene expression and hence patterning of the facial primordia.
authors.affiliation: Department of Craniofacial Development, Guy's, King's, and St Thomas' School of Dentistry, Guy's Hospital, London, United Kingdom.
authors.forename: A J
authors.initials: AJ
authors.lastname: Barlow
authors.forename: J P
authors.initials: JP
authors.lastname: Bogardi
authors.forename: R
authors.initials: R
authors.lastname: Ladher
authors.forename: P H
authors.initials: PH
authors.lastname: Francis-West
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D019485:Bone Morphogenetic Proteins / Q000235:genetics*; D001842:Bone and Bones / Q000196:embryology; D002642:Chick Embryo; D003001:Cloning, Molecular; D004622:Embryo, Mammalian / Q000033:anatomy & histology / Q000378:metabolism; D005145:Face / Q000196:embryology; D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000378:metabolism*; D017403:In Situ Hybridization; D051957:MSX1 Transcription Factor; D008437:Maxilla / Q000196:embryology*; D051379:Mice; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: C095587:Barx1 protein, mouse; D019485:Bone Morphogenetic Proteins; D018398:Homeodomain Proteins; D051957:MSX1 Transcription Factor; D014157:Transcription Factors; D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors