Expression of c-jun proto-oncogene in corneal endothelium

The cellular proto-oncogenes are important for proliferation, differentiation and transformation. To study growth regulation of bovine corneal endothelium (BCE), the authors examined the effect of serum on the expression of the c-jun proto-oncogene in these cells. Increased expression of both c-jun protein and c-jun mRNA was found. This response was transient. While the mRNA reached maximum levels at 45 min, c-jun protein levels peaked around 2 hr and declined thereafter. The peptide growth factors, basic fibroblast growth factor (FGF-2), insulin and transforming growth factor beta 1 (TGF beta 1), which are mitogenic in BCE, were found to effect c-jun protein expression differentially. Basic fibroblast growth factor and 20% fetal calf serum were very effective in inducing c-jun protein expression (in 81% +/- 5.2, 73% +/- 3.4 of cells, respectively), while insulin and TGF beta 1 were less effective (47% +/- 8.0, 32% +/- 4.3, respectively). Since c-jun protein has been shown to be important for cell cycle progression in fibroblasts, our data indicate that it may play a similar role in corneal endothelial cells. Thus, c-jun can be used as an indicator of growth regulatory activity in corneal endothelial cells and further analysis of its regulation will contribute to our understanding of the underlying control mechanisms in these cells.