A 55 bp segment of exon 2 was replaced with a cassette containing IRES, lacZ, and a floxed PGK-neomycin resistance gene. The DNA binding domain was disrupted and a frame shift was created in the process. A shorter mRNA transcript in which exon 1 is spliced directly to exon 3 was detected by Northern blot analysis. Immunoblot analysis indicated the absence of any protein product. Beta-galactosidase expression was not detected. (J:88534)