Cardiotrophin-1 maintains the undifferentiated state in skeletal myoblasts.
Skeletal myogenesis is potently regulated by the extracellular milieu of growth factors and cytokines. We observed that cardiotrophin-1 (CT-1), a member of the interleukin-6 (IL-6) family of cytokines, is a potent regulator of skeletal muscle differentiation. The normal up-regulation of myogenic marker genes, myosin heavy chain (MyHC), myogenic regulatory factors (MRFs), and myocyte enhancer factor 2s (MEF2s) were inhibited by CT-1 treatment. CT-1 also represses myogenin (MyoG) promoter activation. CT-1 activated two signaling pathways: signal transducer and activator of transcription 3 (STAT3), and mitogen-activated protein kinase kinase (MEK), a component of the extracellular signal-regulated MAPK (ERK) pathway. In view of the known connection between CT-1 and STAT3 activation, we surprisingly found that pharmacological blockade of STAT3 activity had no effect on the inhibition of myogenesis by CT-1 suggesting that STAT3 signaling is dispensable for myogenic repression. Conversely, MEK inhibition potently reversed the inhibition of myotube formation and attenuated the repression of MRF transcriptional activity mediated by CT-1. Taken together, these data indicate that CT-1 represses skeletal myogenesis through interference with MRF activity by activation of MEK/ERK signaling. In agreement with these in vitro observations, exogenous systemic expression of CT-1 mediated by adenoviral vector delivery increased the number of myonuclei in normal post-natal mouse skeletal muscle and also delayed skeletal muscle regeneration induced by cardiotoxin injection. The expression pattern of CT-1 in embryonic and post-natal skeletal muscle and in vivo effects of CT-1 on myogenesis implicate CT-1 in the maintenance of the undifferentiated state in muscle progenitor cells.
Miyake
Tetsuaki
T
Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada.
Alli
Nezeka S
NS
Aziz
Arif
A
Knudson
Jennifer
J
Fernando
Pasan
P
Megeney
Lynn A
LA
McDermott
John C
JC
D000818:Animals; D015153:Blotting, Western; D002070:Butadienes / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D016207:Cytokines / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D047468:Immunoprecipitation; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D051379:Mice; D024510:Muscle Development / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D032448:Myoblasts, Skeletal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018006:Myogenic Regulatory Factors / Q000235:genetics / Q000378:metabolism; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011994:Recombinant Proteins / Q000494:pharmacology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection
D002070:Butadienes; D016207:Cytokines; D004791:Enzyme Inhibitors; D005419:Flavonoids; D018006:Myogenic Regulatory Factors; D009570:Nitriles; D011994:Recombinant Proteins; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; C113580:U 0126; D049452:Green Fluorescent Proteins; C092073:cardiotrophin 1; D048369:MAP Kinase Kinase 1; C482127:Map2k1 protein, mouse; D018995:Myosin Heavy Chains; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one