A loxP site was inserted upstream of exon 14 and a FRT-flanked neomycin selection cassette and a second loxP site were inserted downstream of exon 14. Flp-mediated recombination removed the selection cassette. Cre-mediated recombination removed exon 14 which encodes for part of the beta-propeller domain. Western blot analysis confirmed absence of protein in the liver of homozygotes. (J:234556)