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  • Title: Inhibition of FGF-induced alphaA-crystallin promoter activity in lens epithelial explants by TGFbeta.
    Author: Ueda Y, Chamberlain CG, Satoh K, McAvoy JW.
    Journal: Invest Ophthalmol Vis Sci; 2000 Jun; 41(7):1833-9. PubMed ID: 10845606.
    Abstract:
    PURPOSE: Fibroblast growth factor (FGF) plays a key role in normal lens biology, and recent studies suggest that transforming growth factor (TGF)-beta is involved in the origin of certain forms of cataract. In the current study, the effects of FGF and TGFbeta on alphaA-crystallin promoter activity were investigated. METHODS: Rat lens epithelial explants were cultured with or without growth factors after transfecting with the firefly luciferase reporter gene driven by either the mouse alphaA-crystallin promoter region or a control simian virus (SV)40 promoter. RESULTS: FGF-2, at a concentration that induced lens fiber differentiation, strongly stimulated alphaA-crystallin promoter activity in explants at 3 to 4 days of culture, whereas SV40 promoter control specimens showed no comparable increase. At lower concentrations of FGF, sufficient to induce cell proliferation but not differentiation, there was only a slight increase in alphaA-crystallin promoter activity. Stimulation of alphaA-crystallin promoter activity induced by the fiber-differentiating concentration of FGF was virtually abolished by as little as 25 pg/ml TGFbeta2, but the onset of fiber-specific beta-crystallin accumulation was not prevented at this concentration. Phase-contrast microscopy revealed overt cataractous changes only at concentrations of TGFbeta more than 25 pg/ml. CONCLUSIONS: The stimulation of alphaA-crystallin promoter activity by FGF is consistent with its role in inducing accumulation of crystallins in explants. The blocking effect of TGFbeta on this process, even at a concentration too low to induce obvious pathologic changes, indicates the potential for TGFbeta to disturb alphaA-crystallin gene expression during early fiber differentiation.
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