A loxP site was inserted upstream of exon 1 and an FRT flanked neo cassette and second loxP site were inserted downstream of exon 2 via homologous recombination. Recombinase mediated recombination removed exons 1 and 2 and the neo cassette. Western blot analysis confirmed the absence of protein expression in the hearts and kidneys of homozygous mice. (J:165541)