Growth and differentiation of C2 myogenic cells are dependent on serum response factor.
In order to study to what extent and at which stage serum response factor (SRF) is indispensable for myogenesis, we stably transfected C2 myogenic cells with, successively, a glucocorticoid receptor expression vector and a construct allowing for the expression of an SRF antisense RNA under the direction of the mouse mammary tumor virus long terminal repeat. In the clones obtained, SRF synthesis is reversibly down-regulated by induction of SRF antisense RNA expression by dexamethasone, whose effect is antagonized by the anti-hormone RU486. Two kinds of proliferation and differentiation patterns have been obtained in the resulting clones. Some clones with a high level of constitutive SRF antisense RNA expression are unable to differentiate into myotubes; their growth can be blocked by further induction of SRF antisense RNA expression by dexamethasone. Other clones are able to differentiate and are able to synthesize SRF, MyoD, myogenin, and myosin heavy chain at confluency. When SRF antisense RNA expression is induced in proliferating myoblasts by dexamethasone treatment, cell growth is blocked and cyclin A concentration drops. When SRF antisense RNA synthesis is induced in arrested confluent myoblasts cultured in a differentiation medium, cell fusion is blocked and synthesis of not only SRF but also MyoD, myogenin, and myosin heavy chain is inhibited. Our results show, therefore, that SRF synthesis is indispensable for both myoblast proliferation and myogenic differentiation.
Institut Cochin de Génétique Moléculaire, U129 Institut National de la Santé et de la Recherche Médicale, Paris, France.
M
M
Soulez
C G
CG
Rouviere
P
P
Chafey
D
D
Hentzen
M
M
Vandromme
N
N
Lautredou
N
N
Lamb
A
A
Kahn
D
D
Tuil
D000818:Animals; D001358:Avian Sarcoma Viruses; D015415:Biomarkers; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002999:Clone Cells; D016213:Cyclins / Q000096:biosynthesis; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000502:physiology*; D003907:Dexamethasone / Q000494:pharmacology; D006801:Humans; D008324:Mammary Tumor Virus, Mouse; D051379:Mice; D009132:Muscles; D017570:MyoD Protein / Q000096:biosynthesis; D018008:Myogenin / Q000096:biosynthesis; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000502:physiology*; D011401:Promoter Regions, Genetic; D011965:Receptors, Glucocorticoid / Q000096:biosynthesis*; D011994:Recombinant Proteins / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D026362:Serum Response Factor; D014162:Transfection
D015415:Biomarkers; D016213:Cyclins; D004268:DNA-Binding Proteins; C503799:MYOG protein, human; D017570:MyoD Protein; C503801:Myog protein, mouse; D018008:Myogenin; D009687:Nuclear Proteins; D011965:Receptors, Glucocorticoid; D011994:Recombinant Proteins; D026362:Serum Response Factor; D003907:Dexamethasone