EXPRESSION OF TYPE-I AND TYPE-IV COLLAGEN GENES IN NORMAL AND IN MODULATED CORNEAL ENDOTHELIAL-CELLS

  • 1 February 1989
    • journal article
    • research article
    • Vol. 30  (2) , 260-268
Abstract
Expression of type I and type IV collagen genes was studied in normal endothelial cells and in modulated endothelial cells (formerly designated as fibroblastic corneal endothelial cells: FCEC). There appear to be distinct collagen phenotypes in these cells; normal cells produce type IV collagen as a major type, while the modulated cells produce predominantly type I collagen. The absence of type I synthesis in normal cells, and absence of type IV collagen in FCEC were confirmed by immunoblot analysis of the accumulated collagen in the cellular and medium layers in cultures of these cells. When collagen mRNAs were translated in a cell-free system, the results indicate that neither type I collagen RNAs in the normal cells, nor type IV collagen RNAs in the modulated cells were translated. Using cloned cDNA probes, the relative quantities of transcripts of these collagens were determined by slot blot hybridization; normal cells, which synthesize no detectable type I collagen, were found to contain type I collagen RNAs in similar amounts as did the modulated cells, while the levels of type IV RNAs in modulated cells were as high as those in normal cells, in spite of the absence of their translational products. Northern blot analysis demonstrated that there are no distinct differences in the size of type I collagen RNAs in the normal and modulated cells. In contrast, type IV collagen RNA in the modulated cells was much smaller than the normal cells, suggesting that the .alpha.1(IV) RNA is readily degraded. Our data indicate that there is, at least in part, translational control of collagen expression in endothelial cells; the amounts of mRNAs do not correspond to the amounts of the translated proteins. Nevertheless, the mechanisms for the regulation in type I collagen expression may be different from those controlling type IV collagen expression.

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