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M. K. Duncan, J. R. Taube, A. Kiss, A. Yallowitz, Y. Wang; DeltaEF1 as a Potential Modulator of Emt in the Lens. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5642.
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Epithelial-mesenchymal transition (EMT) of lens epithelial cells has been established as a primary cause of both anterior subcapsular cataract and posterior capsular opacification following cataract surgery. Recently, deltaEF1, a transcription factor first shown to repress delta crystallin gene transcription in the chicken lens, has been shown to activate alpha smooth muscle actin expression during EMT in non-lens cells. Here we test the hypothesis that deltaEF1 is involved in EMT in the lens.
The expression pattern of deltaEF1 and alpha smooth muscle actin was determined in the mouse and chicken lens by confocal immunofluorescence and compared to that following extracapsular extraction of lens fiber cells from mouse eyes. Transfac searches were used to identify potential deltaEF1 binding sites in the chicken betaB1-crystallin promoter and transfection analysis was used to test the ability of deltaEF1 to regulate betaB1-crystallin expression.
DeltaEF1 is abundantly expressed in the chicken lens during early development while its expression level decreases sharply prior to hatching. In contrast, deltaEF1 is largely absent from the mouse lens although occasional deltaEF1 positive cells are detected in the equatorial epithelium. deltaEF1 and alpha-smooth muscle actin expression upregulate sharply in the mouse lens 1-2 days following extracapsular fiber cell extraction consistent with a role for deltaEF1 in lens EMT. The chicken betaB1-crystallin promoter contains three consensus deltaEF1 binding sites and deltaEF1 repressed chicken betaB1 crystallin promoter activity in co-transfection analysis. Further, mutation of these sites increased betaB1-crystallin promoter activity in primary chicken lens epithelial cells which contain endogenous deltaEF1 expression.
As previously reported, the chicken lens contains appreciable amounts of endogenous deltaEF1 while the mouse lens does not. However, deltaEF1 expression is induced coincident with alpha smooth muscle actin in the mouse lens following extracapsular fiber cell removal. Since the fiber cell specific betaB1-crystallin promoter contains functional deltaEF1 binding sites, these data suggests that deltaEF1 plays roles in both repressing the expression of lens fiber cell markers and activating alphaSmooth muscle actin expression during EMT in the lens.
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