Exon 2 was flanked by loxP sites and an FRT-flanked PGK-neomycin selection cassette was introduced following the second loxP site. Flp-mediated recombination removed the selection cassette. Cre-mediated recombination removed exon 2 causing a frame-shift mutation with a premature translational termination producing a transcript encoding only the first 14 amino acids. (J:241850)