Neurofibromatosis 2 (NF2) is an autosomal dominant inherited disorder that predisposes to benign tumors of the nervous system as well as a variety of ocular abnormalities. In contrast to NF1, NF2 is associated with only minor developmental abnormalities. The human NF2 gene encodes a tumor suppressor protein, termed schwannomin or merlin, which is a member of a superfamily of proteins thought to link cytoskeletal elements to cell membrane components. To determine the pattern of NF2 gene expression in mouse embryos, we sequenced the mouse NF2 gene and used in situ hybridization and antischwannomin antibodies to determine the developmental expression of the NF2 gene. Schwannomin was detected in most differentiated tissues but was undetectable in undifferentiated tissues. In particular, schwannomin was not detectable in mitotic neuroepithelial cells, the perichondrium, the liver, the neocortex, and the ventricular zone of the developing cerebral cortex. In the heart, expression was observed in all developmental stages beginning on embryonic day 8. In the eye, which shows developmental abnormalities in NF2 patients, expression was detected in the cells of the lens and in the pigment epithelium but weakly detected in retinal neurons. The most striking example of tightly regulated NF2 expression was observed in cells migrating from the ventricular zone to the cortical plate on embryonic days 15 and 16. Only cells in the intermediate zone expressed schwannomin, indicating that schwannomin may play an important role in cellular migration.