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Differential control of muscle-specific gene expression specified by src and myc oncogenes in myogenic cells
G Falcone1, M C Gauzzi, F Tatò
1Istituto di Biologia Cellulare, C.N.R., Roma, Italy.
Abstract:
Myogenic cells can be transformed in vitro by the introduction of several exogenous viral oncogenes. Transformed myoblasts are prevented from terminal differentiation into myotubes by the continuous expression of oncogenes such as myc and src, chosen as prototypes of nuclear and cytoplasmic oncogenes. A comparative analysis of the relationship between transformation and differentiation in myoblasts and cells belonging to other lineages has led to the proposal that terminal differentiation of myc-transformed quail myoblasts is indirectly prevented by the loss of growth control and that myc-bearing cells remain susceptible to growth regulation by interaction with adjacent normal cells. On the contrary, the src oncogene appears to affect expression of the myogenic programme via a direct mechanism, independent from abnormal growth control. There is increasing evidence for the existence of master regulatory genes that govern and influence muscle development in vivo and myogenic differentiation in vitro. Expression of cytoplasmic oncogenes such as src, ras and polyoma middle T in the mouse myogenic cell line, C2, results in inhibition of biochemical differentiation and a marked down-regulation of the MyoD1 and myogenin genes.
Insights
Viral oncogenes like myc and src block muscle cell differentiation. Myc-transformed cells lose growth control, while src directly inhibits the myogenic program, impacting key muscle development genes.
Area of Science:
- Molecular Biology
- Cell Biology
- Developmental Biology
Background:
- Myogenic cells differentiate into muscle cells (myotubes) but can be altered by viral oncogenes.
- Oncogenes, such as myc and src, can disrupt normal cellular processes, including differentiation.
Purpose of the Study:
- To investigate how viral oncogenes affect myogenic cell differentiation.
- To compare the mechanisms by which nuclear (myc) and cytoplasmic (src) oncogenes inhibit muscle cell terminal differentiation.
Main Methods:
- In vitro transformation of myogenic cells with viral oncogenes.
- Comparative analysis of differentiation pathways in normal and oncogene-transformed cells.
- Assessment of gene expression, including MyoD1 and myogenin, in response to oncogene expression.
Main Results:
- Continuous expression of myc or src prevents myoblast differentiation into myotubes.
- Myc-transformed cells show indirect inhibition via loss of growth control, retaining some growth regulation.
- Src oncogene directly inhibits the myogenic program, independent of growth control, down-regulating MyoD1 and myogenin.
Conclusions:
- Viral oncogenes differentially regulate myogenic differentiation.
- Myc oncogene's effect is indirect, linked to growth control disruption.
- Src oncogene directly interferes with the myogenic differentiation program, affecting key regulatory genes.