Failure of Myf5 to support myogenic differentiation without myogenin, MyoD, and MRF4

M. Renee Valdez, James A. Richardson, William H. Klein, Eric N. Olson

Research output: Contribution to journalArticle

90 Citations (Scopus)

Abstract

The basic helix-loop-helix (bHLH) transcription factors - MyoD, Myf5, myogenin, and MRF4 - can each activate the skeletal muscle-differentiation program in transfection assays. However, their functions during embryogenesis, as revealed by gene-knockout studies in mice, are distinct. MyoD and Myf5 have redundant functions in myoblast specification, whereas myogenin and either MyoD or MRF4 are required for differentiation. Paradoxically, myoblasts from myogenin mutant or MyoD/MRF4 double-mutant neonates differentiate normally in vitro, despite their inability to differentiate in vivo, suggesting that the functions of the myogenic bHLH factors are influenced by the cellular environment and that the specific myogenic defects observed in mutant mice do not necessarily reflect essential functions of these factors. Understanding the individual roles of these factors is further complicated by their ability to cross-regulate one another's expression. To investigate the functions of Myf5 in the absence of contributions from other myogenic bHLH factors, we generated triple-mutant mice lacking myogenin, MyoD, and MRF4. These mice appear to contain a normal number of myoblasts, but in contrast to myogenin or MyoD/MRF4 mutants, differentiated muscle fibers fail to form in vivo and myoblasts from neonates of this triple-mutant genotype are unable to differentiate in vitro. These results suggest that physiological levels of Myf5 are insufficient to activate the myogenic program in the absence of other myogenic factors and suggest that specialized functions have evolved for the myogenic bHLH factors to switch on the complete program of muscle gene expression. (C) 2000 Academic Press.

Original languageEnglish (US)
Pages (from-to)287-298
Number of pages12
JournalDevelopmental Biology
Volume219
Issue number2
DOIs
StatePublished - Mar 15 2000

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Myogenin
Myoblasts
Basic Helix-Loop-Helix Transcription Factors
Muscles
Gene Knockout Techniques
Embryonic Development
Transfection
Skeletal Muscle
Genotype
myogenic factor 6
Gene Expression

ASJC Scopus subject areas

  • Developmental Biology

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Failure of Myf5 to support myogenic differentiation without myogenin, MyoD, and MRF4. / Valdez, M. Renee; Richardson, James A.; Klein, William H.; Olson, Eric N.

In: Developmental Biology, Vol. 219, No. 2, 15.03.2000, p. 287-298.

Research output: Contribution to journalArticle

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