A retinoic acid response element (RARE) lies about 1-kb upstream from the coding sequence of the gene. The response element was replaced by a floxed neo cassette. Chimeric males bearing the targeted allele were crossed with transgenic mice expressing cre-recombinase to remove the neo-cassette. Whole-mount in situ hybridization revealed reduced expression of the gene locus during embryonic development including in the primitive streak phase and during formation of the neuroectoderm. (J:86514)