MUTATION OF THE EMX-1 HOMEOBOX GENE DISRUPTS THE CORPUS-CALLOSUM

Expression of the Emx-1 homeobox gene is largely restricted to the dev eloping and mature cerebral cortex. To study its function, two lines o f mice were generated using gene targeting methods that have a deletio n that includes the N-terminal coding region of Emx-1. Mice homozygous for the deletion were viable and fertile and exhibited no obvious beh avioral defects, However, 100% of homozygous mice lack most or all of their corpus callosum, the principle fiber tract that connects the lef t and right cerebral hemispheres. Heterozygotes show partial penetranc e for the corpus callosum abnormality, The histology and various molec ular properties of the cerebral cortex appear normal in the mutant mic e. (C) 1996 Academic Press, Inc.