The targeting vector was designed to insert a loxP site 5' of exon 1 and a loxP-flanked neomycin cassette in intron 2. Exons 1 and 2 comprise the full length gene. Cre-mediated recombination removed the floxed region. Quantitative RT-PCR analysis did not detect mRNA in homozygous mutant mice. (J:203783)