title: Expression of (beta)-catenin in the developing chick myotome is regulated by myogenic signals.
abstract: The developmental signals that govern cell specification and differentiation in vertebrate somites are well understood. However, little is known about the downstream signalling pathways involved. We have shown previously that a combination of Shh protein and Wnt1 or Wnt3a-expressing fibroblasts is sufficient to activate skeletal muscle-specific gene expression in somite explants. Here, we have examined the molecular mechanisms by which the Wnt-mediated signal acts on myogenic precursor cells. We show that chick frizzled 1 (Fz1), beta-catenin and Lef1 are expressed during somitogenesis. Lef1 and beta-catenin transcripts become restricted to the developing myotome. Furthermore, beta-catenin is expressed prior to the time at which MyoD transcripts can be detected. Expression of beta-catenin mRNA is regulated by positive and negative signals derived from neural tube, notochord and lateral plate mesoderm. These signals include Bmp4, Shh and Wnt1/Wnt3a itself. In somite explants, Fz1, beta-catenin and Lef1 are expressed prior to activation of myogenesis in response to Shh and Wnt signals. Thus, our data show that a combination of Shh and Wnt1 upregulates expression of Wnt pathway components in developing somites prior to myogenesis. Thus, Wnt1 could act through beta-catenin on cells in the myotome.
authors.affiliation: Division of Cell and Developmental Biology, Department of Anatomy and Physiology, Wellcome Trust Biocentre, University of Dundee, Dow Street, Dundee DD1 5EH, UK.
authors.forename: M
authors.initials: M
authors.lastname: Schmidt
authors.forename: M
authors.initials: M
authors.lastname: Tanaka
authors.forename: A
authors.initials: A
authors.lastname: Münsterberg
mesh_terms: D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology; D002642:Chick Embryo; D003598:Cytoskeletal Proteins / Q000096:biosynthesis*; D004268:DNA-Binding Proteins / Q000378:metabolism; D029721:Drosophila Proteins; D004627:Embryonic Induction; D051157:Frizzled Receptors; D053823:Hedgehog Proteins; D066298:In Vitro Techniques; D051821:Lymphoid Enhancer-Binding Factor 1; D008565:Membrane Proteins / Q000378:metabolism; D008648:Mesoderm / Q000378:metabolism; D018482:Muscle, Skeletal / Q000196:embryology*; D017570:MyoD Protein / Q000378:metabolism; D018006:Myogenic Regulatory Factors / Q000378:metabolism*; D009420:Nervous System / Q000196:embryology / Q000378:metabolism; D009672:Notochord / Q000196:embryology / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled; D015398:Signal Transduction; D019170:Somites / Q000378:metabolism; D015534:Trans-Activators; D014157:Transcription Factors / Q000378:metabolism; D051153:Wnt Proteins; D051155:Wnt1 Protein; D060508:Wnt3 Protein; D029961:Zebrafish Proteins; D051176:beta Catenin
chemical_list: D019485:Bone Morphogenetic Proteins; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D051157:Frizzled Receptors; D053823:Hedgehog Proteins; D051821:Lymphoid Enhancer-Binding Factor 1; D008565:Membrane Proteins; D017570:MyoD Protein; D018006:Myogenic Regulatory Factors; D011506:Proteins; D011518:Proto-Oncogene Proteins; D043562:Receptors, G-Protein-Coupled; D015534:Trans-Activators; D014157:Transcription Factors; D051153:Wnt Proteins; D051155:Wnt1 Protein; D060508:Wnt3 Protein; D029961:Zebrafish Proteins; D051176:beta Catenin; C058784:fz protein, Drosophila