MyoR: A muscle-restricted basic helix–loop–helix transcription factor that antagonizes the actions of MyoD Academic Article uri icon


  • Skeletal muscle development is controlled by a family of muscle-specific basic helix-loop-helix (bHLH) transcription factors that activate muscle genes by binding E-boxes (CANNTG) as heterodimers with ubiquitous bHLH proteins, called E proteins. Myogenic bHLH factors are expressed in proliferating undifferentiated myoblasts, but they do not initiate myogenesis until myoblasts exit the cell cycle. We describe a bHLH protein, MyoR (for myogenic repressor), that is expressed in undifferentiated myoblasts in culture and is down-regulated during differentiation. MyoR is also expressed specifically in the skeletal muscle lineage between days 10.5 and 16.5 of mouse embryogenesis and down-regulated thereafter during the period of secondary myogenesis. MyoR forms heterodimers with E proteins that bind the same DNA sequence as myogenic bHLH/E protein heterodimers, but MyoR acts as a potent transcriptional repressor that blocks myogenesis and activation of E-box-dependent muscle genes. These results suggest a role for MyoR as a lineage-restricted transcriptional repressor of the muscle differentiation program.

author list (cited authors)

  • Lu, J., Webb, R., Richardson, J. A., & Olson, E. N.

citation count

  • 132

publication date

  • January 1999


  • Amino Acid Sequence
  • Animals
  • Cell Differentiation
  • Cells, Cultured
  • Cloning, Molecular
  • DNA-Binding Proteins
  • Dimerization
  • Embryonic And Fetal Development
  • Gene Expression Regulation, Developmental
  • Helix-loop-helix Motifs
  • In Situ Hybridization
  • Mice
  • Molecular Sequence Data
  • Muscle Development
  • Muscle Proteins
  • Muscle, Skeletal
  • MyoD Protein
  • Myogenin
  • RNA, Messenger
  • Sequence Analysis, DNA
  • Sequence Homology, Amino Acid
  • Transcription Factors
  • Transfection