UNIVERSAL ABSENCE OF MERLIN, BUT NOT OTHER ERM FAMILY MEMBERS, IN SCHWANNOMAS

NF2 (neurofibromatosis 2, encoding the merlin protein) gene mutations and chromosome 22q loss have been demonstrated in the majority of spor adic and NF2-associated schwannomas, but many schwannomas fail to demo nstrate genetic evidence of biallelic NF2 gene inactivation, In additi on, the role of the merlin-related ERM family members (ezrin, radixin, and moesin) remains unclear in these tumors. We therefore studied exp ression of NF2-encoded merlin as well as ezrin, radixin, and moesin in 22 vestibular and peripheral schwannomas that had been evaluated for NF2 mutations and chromosome 22q loss. Western blotting and immunohist ochemistry with antibodies directed against the amino and carboxy term ini of merlin demonstrated loss of merlin expression in all studied sc hwannomas, including 12 tumors lacking genetic evidence of biallelic N F2 gene inactivation, Western blotting with antibodies directed agains t ezrin, radixin, and moesin, however, showed expression of these prot eins in all schwannomas. In addition, immunohistochemistry with an ant ibody to moesin revealed widespread expression in tumor and endothelia l cells. These data indicate that the specific loss of merlin is unive rsal to schwannomas and is not licked to loss of ezrin, radixin, or mo esin expression.