Expression of (beta)-catenin in the developing chick myotome is regulated by myogenic signals.
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.
Schmidt
M
M
Division of Cell and Developmental Biology, Department of Anatomy and Physiology, Wellcome Trust Biocentre, University of Dundee, Dow Street, Dundee DD1 5EH, UK.
Tanaka
M
M
Münsterberg
A
A
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
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