Differential expression of N- and B-cadherin during lens development.

PURPOSE To analyze the dynamics of N- and B-cadherin cell adhesion molecule expression and cytoskeletal interaction during embryonic chick lens development. METHODS Localization of N- and B-cadherin, F-actin, and connexin 56 were determined by immunohistochemistry of developing lenses or immunocytochemistry of differentiating primary lens cultures. Biochemical analysis of cytoskeletal linkage of N- or B-cadherin was assessed by differential detergent extraction, electrophoresis, and immunoblotting. RESULTS The results indicate that although both cadherins are expressed throughout lens development, N-cadherin expression detected was similar in both lens epithelial and fiber cells, whereas B-cadherin was preferentially localized to the lens fiber cells. During differentiation, both cadherins become increasingly associated with the lens cytoskeleton, as indicated biochemically by a transition from largely Triton X-100-soluble to Triton X-100-insoluble pools and immunocytologically by cadherin localization to cell-cell borders and colocalization with the actin cytoskeleton. Although a significant fraction of N-cadherin remains Triton X-100-soluble as the lens cells differentiate, B-cadherin becomes resistant to extraction by both Triton X-100 as well as RIPA buffers. As detected immunocytochemically in lens cell cultures, the temporal localization of N-cadherin to cell-cell interfaces precedes that of B-cadherin. Furthermore, temporal localization of B-cadherin, as opposed to N-cadherin, to cell-cell borders more closely parallels that of connexin 56 in vitro as well as in vivo. CONCLUSIONS; These results suggest that while both N- and B-cadherin are expressed during lens cell differentiation, both their patterns of expression as well as their cytoskeletal association differ between epithelial and fiber cells.