Tbx6, Mesp-b and Ripply1 regulate the onset of skeletal myogenesis in zebrafish.
During embryonic development, the paraxial mesoderm becomes segmented into somites, within which proliferative muscle progenitors and muscle fibers establish the skeletal musculature. Here, we demonstrate that a gene network previously implicated in somite boundary formation, involving the transcriptional regulators Tbx6, Mesp-b and Ripply1, also confers spatial and temporal regulation to skeletal myogenesis in zebrafish. We show that Tbx6 directly regulates mesp-b and ripply1 expression in vivo, and that the interactions within the regulatory network are largely conserved among vertebrates. Mesp-b is necessary and sufficient for the specification of a subpopulation of muscle progenitors, the central proportion of the Pax3(+)/Pax7(+) dermomyotome. Conditional ubiquitous expression indicates that Mesp-b acts by inhibiting myogenic differentiation and by inducing the dermomyotome marker meox1. By contrast, Ripply1 induces a negative-feedback loop by promoting Tbx6 protein degradation. Persistent Tbx6 expression in Ripply1 knockdown embryos correlates with a deficit in dermomyotome and myotome marker gene expression, suggesting that Ripply1 promotes myogenesis by terminating Tbx6-dependent inhibition of myogenic maturation. Together, our data suggest that Mesp-b is an intrinsic upstream regulator of skeletal muscle progenitors and that, in zebrafish, the genes regulating somite boundary formation also regulate the development of the dermomyotome in the anterior somite compartment.
Department of Biology, Wesleyan University, Middletown, CT 06459, USA.
Stefanie E
SE
Windner
Department of Biology, Wesleyan University, Middletown, CT 06459, USA.
Rosemarie A
RA
Doris
Department of Biology, Wesleyan University, Middletown, CT 06459, USA.
Chantal M
CM
Ferguson
Randall Division of Cell and Molecular Biophysics, New Hunt's House, King's College London, Guy's Campus, London, SE1 1UL, UK.
Andrew C
AC
Nelson
MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA, UK.
Guillaume
G
Valentin
Randall Division of Cell and Molecular Biophysics, New Hunt's House, King's College London, Guy's Campus, London, SE1 1UL, UK.
Haihan
H
Tan
MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA, UK.
Andrew C
AC
Oates
Randall Division of Cell and Molecular Biophysics, New Hunt's House, King's College London, Guy's Campus, London, SE1 1UL, UK.
Fiona C
FC
Wardle
Department of Biology, Wesleyan University, Middletown, CT 06459, USA sdevoto@wesleyan.edu.
Stephen H
SH
Devoto
D000818:Animals; D030801:Animals, Genetically Modified; D000911:Antibodies, Monoclonal; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism*; D047369:Chromatin Immunoprecipitation; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology*; D055785:Gene Knockdown Techniques; D053263:Gene Regulatory Networks / Q000235:genetics / Q000502:physiology; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D060172:Morpholinos / Q000235:genetics; D024510:Muscle Development / Q000502:physiology*; D018482:Muscle, Skeletal / Q000196:embryology*; D009687:Nuclear Proteins / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D019170:Somites / Q000196:embryology; D020825:T-Box Domain Proteins / Q000276:immunology / Q000378:metabolism*; D015027:Zebrafish / Q000196:embryology*; D029961:Zebrafish Proteins / Q000276:immunology / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D051792:Basic Helix-Loop-Helix Proteins; D060172:Morpholinos; D009687:Nuclear Proteins; D020825:T-Box Domain Proteins; D029961:Zebrafish Proteins; C410085:mespba protein, zebrafish; C507062:ripply1 protein, zebrafish; C491180:tbx6 protein, zebrafish
Dermomyotome; Determination front; Gene regulatory network; Heat shock; Maturation; Myotome; Protein degradation; Segmentation; Wavefront; Zebrafish