A targeting vector was designed to insert a loxP site, followed by a FRT-flanked neomycin resistance (neo) cassette, upstream of exon 2, and a second loxP site downstream of exon 2. Flp-mediated recombination removed the FRT-flanked neo cassette leaving exon 2 floxed. Cre-mediated recombination removed exon 2, which is predicted to cause a frameshift mutation resulting in a truncated product. Western blot analysis confirmed the absence of the 37 kD protein.