The targeting event deleted a part of exon 1 containing the translation initiation codon, replacing it with a DNA segment containing a lacZ gene and a Pgk-neo cassette. The bacterial beta-galactosidase is not expressed in vivo. RT-PCR analysis of homozygous mutant mice amplified no transcript, and immunoblot analysis detected only cross-reacting proteins and not the major, specific band. (J:102528)