Inhibition of myogenesis by Notch: evidence for multiple pathways.
Notch signaling is critical for skeletal muscle development and regeneration, permitting the expansion of progenitor cells by preventing premature differentiation. We have interrogated the pathways through which ligand-mediated signaling inhibits myogenesis by identifying Notch target genes and assessing their impact on differentiation in vitro. Notch activation led to the robust induction of the transcriptional repressors Hey1 and HeyL in myoblasts, but only constitutive expression of Hey1 blocked myogenesis. siRNA-mediated knockdown of Hey1 had no effect on Notch's ability to inhibit differentiation, suggesting the existence of additional, possibly redundant pathways. We identified 82 genes whose expression was activated when C2C12 myoblasts were cultured in the presence of the Notch ligand Dll4. One of these, MyoR, is a novel Notch-responsive gene, whose protein product is known to repress myogenesis in vitro. siRNA-mediated knockdown of MyoR alone, or in combination with Hey1, was also ineffective at rescuing differentiation in the presence of Dll4. Our data support a model in which Notch signaling inhibits myogenesis through multiple pathways, two of which are defined by the Notch target genes Hey1 and MyoR.
Buas
Matthew F
MF
Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania.
Kabak
Shara
S
Kadesch
Tom
T
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008024:Ligands; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D024510:Muscle Development / Q000235:genetics / Q000502:physiology*; D032448:Myoblasts, Skeletal / Q000166:cytology / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D051880:Receptors, Notch / Q000378:metabolism*; D015398:Signal Transduction; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D051792:Basic Helix-Loop-Helix Proteins; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D017931:DNA Primers; D047908:Intracellular Signaling Peptides and Proteins; D008024:Ligands; D008565:Membrane Proteins; D034741:RNA, Small Interfering; D051880:Receptors, Notch; D014157:Transcription Factors; C519665:DLL4 protein, mouse; C120420:Hey1 protein, mouse; C117673:Msc protein, mouse