The targeting vector consisting of a loxP site, exon 2, a frt-flanked neomycin cassette, and a loxP site was inserted into the locus. Cre-mediated recombination deleted exon 2 and the neomycin cassette. DNA blot analysis confirmed the presence of the disrupted allele and RT-PCR confirmed ablation of the full-length mRNA expression. Western blot confirmed a complete absence of protein, indicating this is a functionally null allele.