title: Ectodermal Wnt-6 promotes Myf5-dependent avian limb myogenesis.
abstract: Limb muscles of vertebrates are derived from precursor cells that migrate from the lateral edge of the dermomyotome into the limb bud. Although several signaling molecules have been reported to be involved in the process of limb myogenesis, none of their activities has led to a consolidate idea about the limb myogenic pathway. Particularly, the role of ectodermal signals in limb myogenesis is still obscure. Here, we investigated the role of the ectoderm and ectodermal Wnt-6 during limb muscle development. We found that ectopic expression of Wnt-6 in the limb bud specifically extends the expression domains of Pax3, Paraxis, Myf5, Myogenin, Desmin and Myosin heavy chain (MyHC) but inhibits MyoD expression. Ectoderm removal results in a loss of expression of all of these myogenic markers. We show that Wnt-6 can compensate the absence of the ectoderm by rescuing the expression of Pax3, Paraxis, Myf5, Myogenin, Desmin and MyHC but not MyoD. These results show that, in chick, at least two signals from the limb ectoderm are necessary for muscle development. One of the signals is Wnt-6, which plays a unique role in promoting limb myogenesis via Pax3/Paraxis-Myf5, whereas the other putative signaling pathway involving MyoD expression is negatively regulated by Wnt-6 signaling.
authors.affiliation: Institute of Anatomy and Cell Biology, Department of Molecular Embryology, University of Freiburg, Albertstrasse 17, D-79104 Freiburg, Germany.
authors.forename: Poongodi
authors.initials: P
authors.lastname: Geetha-Loganathan
authors.forename: Suresh
authors.initials: S
authors.lastname: Nimmagadda
authors.forename: Felicitas
authors.initials: F
authors.lastname: Pröls
authors.forename: Ketan
authors.initials: K
authors.lastname: Patel
authors.forename: Martin
authors.initials: M
authors.lastname: Scaal
authors.forename: Ruijin
authors.initials: R
authors.lastname: Huang
authors.forename: Bodo
authors.initials: B
authors.lastname: Christ
mesh_terms: D000818:Animals; D030161:Avian Proteins / Q000502:physiology*; D051792:Basic Helix-Loop-Helix Proteins / Q000502:physiology; D002642:Chick Embryo; D004475:Ectoderm / Q000502:physiology*; D005121:Extremities / Q000196:embryology*; D032342:Muscle Cells / Q000502:physiology; D024510:Muscle Development / Q000502:physiology*; D051787:Myogenic Regulatory Factor 5 / Q000502:physiology*; D000072041:PAX3 Transcription Factor; D051761:Paired Box Transcription Factors / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D051153:Wnt Proteins / Q000502:physiology*
chemical_list: D030161:Avian Proteins; D051792:Basic Helix-Loop-Helix Proteins; D051787:Myogenic Regulatory Factor 5; D000072041:PAX3 Transcription Factor; D051761:Paired Box Transcription Factors; D011518:Proto-Oncogene Proteins; D051153:Wnt Proteins; C489409:PAX3 protein, human; C095936:Wnt6 protein, mouse