title: MyoD and Myf-5 differentially regulate the development of limb versus trunk skeletal muscle.
abstract: The myogenic progenitors of epaxial (paraspinal and intercostal) and hypaxial (limb and abdominal wall) musculature are believed to originate in dorsal-medial and ventral-lateral domains, respectively, of the developing somite. To investigate the hypothesis that Myf-5 and MyoD have different roles in the development of epaxial and hypaxial musculature, we further characterized myogenesis in Myf-5- and MyoD-deficient embryos by several approaches. We examined expression of a MyoD-lacZ transgene in Myf-5 and MyoD mutant embryos to characterize the temporal-spatial patterns of myogenesis in mutant embryos. In addition, we performed immunohistochemistry on sectioned Myf-5 and MyoD mutant embryos with antibodies reactive with desmin, nestin, myosin heavy chain, sarcomeric actin, Myf-5, MyoD and myogenin. While MyoD(-/-) embryos displayed normal development of paraspinal and intercostal muscles in the body proper, muscle development in limb buds and brachial arches was delayed by about 2.5 days. By contrast, Myf-5(-/-) embryos displayed normal muscle development in limb buds and brachial arches, and markedly delayed development of paraspinal and intercostal muscles. Although MyoD mutant embryos exhibited delayed development of limb musculature, normal migration of Pax-3-expressing cells into the limb buds and normal subsequent induction of Myf-5 in myogenic precursors was observed. These results suggest that Myf-5 expression in the limb is insufficient for the normal progression of myogenic development. Taken together, these observations strongly support the hypothesis that Myf-5 and MyoD play unique roles in the development of epaxial and hypaxial muscle, respectively.
authors.affiliation: Institute for Molecular Biology and Biotechnology, Cancer Research Group, McMaster University, Hamilton, Ontario, Canada.
authors.forename: B
authors.initials: B
authors.lastname: Kablar
authors.forename: K
authors.initials: K
authors.lastname: Krastel
authors.forename: C
authors.initials: C
authors.lastname: Ying
authors.forename: A
authors.initials: A
authors.lastname: Asakura
authors.forename: S J
authors.initials: SJ
authors.lastname: Tapscott
authors.forename: M A
authors.initials: MA
authors.lastname: Rudnicki
mesh_terms: D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005121:Extremities / Q000196:embryology*; D018507:Gene Expression Regulation, Developmental; D051379:Mice; D008817:Mice, Mutant Strains; D008822:Mice, Transgenic; D009124:Muscle Proteins / Q000502:physiology*; D018482:Muscle, Skeletal / Q000196:embryology* / Q000378:metabolism; D017570:MyoD Protein / Q000502:physiology*; D051787:Myogenic Regulatory Factor 5; D000072041:PAX3 Transcription Factor; D051761:Paired Box Transcription Factors; D013131:Spine / Q000196:embryology*; D013234:Stem Cells / Q000502:physiology; D015534:Trans-Activators; D014157:Transcription Factors; D019076:Transgenes; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D009124:Muscle Proteins; C497418:Myf5 protein, mouse; D017570:MyoD Protein; D051787:Myogenic Regulatory Factor 5; D000072041:PAX3 Transcription Factor; D051761:Paired Box Transcription Factors; D015534:Trans-Activators; D014157:Transcription Factors; C068686:Pax3 protein, mouse; D001616:beta-Galactosidase