Membrane glycoproteins of Philly mouse lens

The Philly mouse is a new model for genetic cataracts, in which there is an apparent defect in lens membrane permeability. This abnormality results in electrolyte imbalance and lens hydration, typical of an osmotic cataract. Since membrane glycoproteins are believed to be involved in transport processes, we have studied the changes in these polypeptides in the Philly mouse lens during cataract development and compared them with those in the control Swiss-Webster mouse. The membrane glycoproteins were labeled by treatment with galactose oxidase and tritiated borohydride. Radioactivity was found to be incorporated into six glycoproteins of approximate molecular weights of 128 k, 103 k, 82 k, 71 k, 35 k, and 22 k daltons. The 35 k polypeptide is the major glycoprotein in the mouse lens membrane and shows increased incorporation of the tritium label with progression of the cataract. In contrast to the murine lens, the 35 k peptide could not be detected in rabbit lens membranes. Other changes observed in glycoproteins of the Philly mouse lens during cataract development were a loss of the 103 k and 71 k polypeptides and a corresponding increase in the 66 k polypeptide. These changes in glycoproteins may be related to the permeability changes and cataract development in the Philly mouse lens.