Divergence of epidermal growth factor - transforming growth factor beta signaling in embryonic orofacial tissue.
The epidermal growth factor (EGF) and transforming growth factor beta (TGFbeta) families of signaling molecules play a major role in growth and development of embryos. Abrogation of either signaling pathway results in defects in embryogenesis, including cleft palate. In the developing palate, both EGF and TGFbeta regulate cellular proliferation, extracellular matrix synthesis, and cellular differentiation but often in an opposing manner. Evidence from various adult cell types suggests the existence of cross talk between the EGF and TGFbeta signaling pathways, although it is unclear whether such cross talk exists in murine embryonic maxillary mesenchymal cells, from which the developing palate is derived. In this study, embryonic maxillary mesenchymal cells in culture were treated with EGF and TGFbeta, either singly or in combination, and the cells were subsequently examined for signaling interactions between these two pathways. Immunoblot analyses of nuclear extracts of embryonic maxillary mesenchymal cells revealed that TGFbeta-induced nuclear translocation of Smad 2 and Smad 3 proteins was not affected by EGF. Conversely, immunoblot analyses of whole-cell extracts of these cells indicated that EGF-induced phosphorylation of extracellular signal-regulated kinase proteins, ERK1 and ERK2, was not affected by TGFbeta. Expression of a transfected luciferase reporter gene driven by a promoter with Smad binding elements was induced by TGFbeta in these cells but was not affected by EGF. Last, TGFbeta was found to induce expression of the endogenous gelatinase B gene in embryonic maxillary mesenchymal cells; however, this effect was independent of any interaction of EGF. Collectively, data from this study suggest that the EGF and TGFbeta signal transduction pathways do not converge in murine embryonic maxillary mesenchymal cells.
Bhattacherjee
Vasker
V
University of Louisville Birth Defects Center, Department of Molecular, Cellular and Craniofacial Biology, University of Louisville School of Dentistry, Louisville, Kentucky 40292, USA. vasker.bhattacherjee@louisville.edu
Greene
Robert M
RM
Michele Pisano
M
M
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation / Q000502:physiology; D004815:Epidermal Growth Factor / Q000378:metabolism*; D015151:Immunoblotting; D008156:Luciferases / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D008437:Maxilla / Q000166:cytology* / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000378:metabolism*; D051379:Mice; D008813:Mice, Inbred ICR; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D051899:Smad2 Protein; D051900:Smad3 Protein; D015534:Trans-Activators / Q000378:metabolism; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000378:metabolism*
D004268:DNA-Binding Proteins; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D004815:Epidermal Growth Factor; D008156:Luciferases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020780:Matrix Metalloproteinase 9