CHANGES IN LENS CONNEXIN EXPRESSION LEAD TO INCREASED GAP JUNCTIONAL VOLTAGE-DEPENDENCE AND CONDUCTANCE

The differentiation of mouse lens epithelial cells into fiber cells is a useful model for studying the changes of the electrical properties of gap junction (cell-to-cell) channels that are induced by an alterat ion in connexin expression patterns. In this model, cuboidal lens epit helial cells differentiate into elongated fiber cells, and the express ion of connexin43 (Cx43) in the epithelial cells is replaced with the production of high levels of Cx50 and Cx46 in the fiber cells. We now report a new procedure to isolate mouse lens fiber cell pairs suitable for double whole cell patch-clamp analysis. Analysis was also perform ed for fiberlike cell pairs differentiated from epithelial cells in cu lture. Voltage dependence and unitary conductance of fiber cell gap ju nction channels were determined and compared with the corresponding va lues previously measured for the channels joining lens epithelial cell s and for lens connexin channels formed in Xenopus oocyte pairs. Our r esults support a differentiation-induced shift toward stronger gap jun ctional voltage dependence and larger unitary conductances in the fibe r cells. Our data further reflect a balanced functional contribution o f Cx50 and Cx46 in the fiber cell-to-cell channels rather than a predo minance of a single connexin.