Expression of schwannomin in lens and Schwann cells.

Neurofibromatosis type 2 (NF2) is an autosomal dominant genetic disorder characterized by the development of bilateral vestibular schwannomas, meningiomas, ependymomas and juvenile lens opacities. The NF2 gene encodes a tumor suppressor protein, schwannomin (or merlin), with sequence homology to erythrocyte band 4.1, talin, ezrin, moesin and radixin. Using an antibody that recognizes the carboxy-terminal epitope of isoform 1 of schwannomin, we looked at its expression in lens and Schwann cells, two cell-types affected by the NF2 phenotype. Schwannomin was detected as an approximately 80 kDa protein in both cytoplasmic and cytoskeleton fractions. Indirect immunofluorescence localized schwannomin to the cytoplasm and was frequently observed in dynamic cellular regions such as leading edges and ruffling membranes. Its level of expression in the lens inversely correlates with the degree of lens cell differentiation suggesting a role for schwannomin in differentiation-specific events.