A neomycin resistance cassette replaced a 687 bp fragment of the gene, which contained the exon encoding MD2. In situ hybridization of parasagittal sections of brains from homozygous mutant mice probed with gene-specific probes showed no detectable mRNA for the targeted gene. Immunoblots of hippocampal membrane extracts from homozygous mutant mice using antibodies against the targeted protein showed no detectable protein. (J:46932)