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Fibroblast growth factor and transforming growth factor beta repress transcription of the myogenic regulatory gene
T B Vaidya1, S J Rhodes, E J Taparowsky
1Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907.
Abstract:
In this report, we demonstrate that myogenic cultures inhibited from differentiating by treatment with fibroblast growth factor or transforming growth factor beta show reduced levels of MyoD1 mRNA. Although this repression may contribute to the inhibition of myogenesis by growth factors, additional regulatory pathways must be affected, since inhibition still occurs in cultures engineered to constitutively express MyoD1 mRNA.
Insights
Fibroblast growth factor and transforming growth factor beta reduce MyoD1 mRNA levels, inhibiting muscle cell differentiation. However, other pathways are involved, as MyoD1 expression alone does not restore myogenesis.
Area of Science:
- Molecular Biology
- Cell Biology
- Developmental Biology
Background:
- Myogenesis, the process of muscle cell differentiation, is tightly regulated by growth factors.
- Fibroblast growth factor (FGF) and transforming growth factor beta (TGF-β) are known inhibitors of myogenesis.
- The transcription factor MyoD1 plays a crucial role in initiating the myogenic program.
Purpose of the Study:
- To investigate the role of MyoD1 mRNA levels in growth factor-mediated inhibition of myogenesis.
- To determine if reduced MyoD1 mRNA is the sole mechanism by which FGF and TGF-β inhibit muscle differentiation.
- To explore the involvement of additional regulatory pathways in growth factor-induced suppression of myogenesis.
Main Methods:
- Treatment of myogenic cultures with FGF or TGF-β.
- Quantification of MyoD1 mRNA levels using quantitative reverse transcription PCR.
- Engineering of myogenic cultures to constitutively express MyoD1 mRNA.
Main Results:
- FGF and TGF-β treatments led to significantly reduced levels of MyoD1 mRNA in myogenic cultures.
- Despite the reduction in MyoD1 mRNA, constitutive expression of MyoD1 did not fully rescue the differentiation defect.
- This indicates that growth factor-induced inhibition of myogenesis involves mechanisms beyond the repression of MyoD1 mRNA.
Conclusions:
- Growth factors FGF and TGF-β inhibit myogenesis partly by downregulating MyoD1 mRNA levels.
- The persistence of inhibition in cultures with constitutively expressed MyoD1 mRNA highlights the involvement of parallel or downstream regulatory pathways.
- Further research is needed to elucidate these additional mechanisms controlling muscle differentiation.