Effects of c‐Jun and a negative dominant mutation of c‐Jun on differentiation and gene expression in lens epithelial cells

We have used a retroviral vector (RCAS) to overexpress wild-type chicken c-Jun or a deletion mutant of chicken c-Jun (Jun delta 7) lacking the DNA binding region to investigate the possible role of c-Jun in lens epithelial cell proliferation and differentiation. Both constructs were efficiently expressed in primary cultures of embryonic chicken lens epithelial cells. Overexpression of c-Jun increased the rate of cell proliferation and greatly delayed the appearance of "lentoid bodies," structures which contain differentiated cells expressing fiber cell markers. Excess c-Jun expression also significantly decreased the level of beta A3/A1-crystallin mRNA, without affecting alpha A-crystallin mRNA. In contrast, the mutated protein, Jun delta 7, had no effect on proliferation or differentiation but markedly increased the level of alpha A-crystallin mRNA in proliferating cell cultures. These results suggest that c-Jun or Jun-related proteins may be negative regulators of alpha A- and beta A3/A1-crystallin genes in proliferating lens cells.