EXPRESSION OF NF2-ENCODED MERLIN AND RELATED ERM FAMILY PROTEINS IN THE HUMAN CENTRAL-NERVOUS-SYSTEM

Germline mutations of the neurofibromatosis 2 (NF2) gene are associate d with an increased incidence of gliomas and glial hamartoma, suggesti ng a role for the NF2-encoded protein, merlin, in glial growth control . Using monoclonal and polyclonal anti-merlin antibodies for Western b lotting and immunohistochemistry, we evaluated the cellular pattern of merlin expression in the normal human central nervous system (CNS), r eactive gliosis, and NF2-associated glial hamartomas. In the normal CN S, merlin is widely expressed in coarse cytoplasmic granules in both g lia and neurons, with less pronounced expression in other cells. Merli n is also expressed in reactive astrocytes and in the astrocytes of NF 2-associated glial hamartomas. In reactive astrocytes, however, merlin is also present at the cell membrane and in cellular processes, sugge sting redistribution of the protein in activated cells. Merlin is stru cturally related to ezrin, radixin and moesin, which are also expresse d in the CNS, as demonstrated by Western blotting. The pattern of merl in expression, however, is distinct from that of ezrin, which has been previously described, and that of moesin, in which immunohistochemist ry with an anti-moesin antibody showed expression in endothelial cells , glia and neurons in a membranous or diffuse cytoplasmic pattern. The se findings imply that merlin has widespread and specific functions in the human central nervous system.