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Effects of EGF and TGF[Beta]1 on regulation of proliferation and expression of immediate early genes in embryonic hamster palate mesenchymal cells Izadnegahdar, Mehrnaz F.


The study was undertaken to investigate: (1) the effects of serum and the growth factors, EGF and TGFb,, and their combination, on the proliferation of embryonic hamster palate mesenchymal cells (HPMC); and (2) the effects of serum, growth factors and their combinations on expression of the immediate early genes, c-fos, c-jun, and c-myc. Initially, growth behavior of the cultured HPMC was examined. The results showed that the proliferation of HPMC was dependent on the concentration of serum in the culture media; and at least 2.5% serum was necessary to sustain the growth of HPMC in culture. EGF supported DNA synthesis (only in the presence of serum), and exerted mitogenic effects on HPMC; whereas TGFb, did not support DNA synthesis and arrested growth of HPMC. In addition, following cotreatment of HPMC with EGF and TGFb, 'the mitogenic effect on HPMC of EGF wasinhibited by TGFb,. Also, 30 minutes of TGFb., pre-treatment was sufficient to irreversibly inhibit the serum- and/or EGF-induced DNA synthesis as well as proliferation of HPMC. Northern blot analysis showed that both serum and EGF induced rapid expression of c-fos, c-jun, and c-myc; whereas TGFb, did not. Also, following co- or pre-treatment with TGFb, the serum- and/or EGF-induced expression of immediate early genes was not inhibited. However, co- or pre-treatment with TGFb, did result in modulations in the temporal expression pattern of these immediate early genes. The results of the present study indicate that EGF and TGFb, are important regulators of embryonic HPMC proliferation. Further,this study suggests that interaction among extracellular factors leads to modulation of the nuclear events that may be important in regulation of HPMC proliferation during palate morphogenesis.

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