Human multidrug resistance 3-P-glycoprotein expression in transgenic mice induces lens membrane alterations leading to cataract.

We have generated mice transgenic for a human multidrug resistance (MDR)3 mini-gene driven by a hamster vimentin promoter. The MDR3 gene encodes a P-Glycoprotein that resembles the mouse multidrug resistance 2 P-Glycoprotein shown to be involved in the translocation of the phospholipid phosphatidylcholine through the hepatocyte canalicular membrane (Smit et al., 1993. Cell. 75:451-462). The vimentin promoter drives expression of the MDR3 transgene in mesenchymal tissues and in the eye lens. We show here that the presence of human multidrug resistance 3 P-Glycoprotein in the lens results in a severe lenticular pathology. Lens structural abnormalities initiate at a late embryonic stage and increase during postnatal lens development. Differentiation of the primary fibers is affected, and the terminal differentiation of the lens epithelium into secondary fibers is also perturbed. The ultrastructural alterations, particularly of the lens plasma membranes, resemble those identified in congenital mouse osmotic cataract.