Exon 1 and 1.6 kb upstream of exon 1 was flanked by loxP sites. An FRT-flanked hygromycin selection cassette was inserted downstream of the floxed region and was removed via flp-mediated recombination. Cre-mediated recombination deleted exon 1 in the germline. Western blot analysis confirmed absence of protein in visceral white adipose tissue. (J:272957)