An FRT-flanked neomycin resistance cassette with a 5' loxP site was inserted upstream of exon 3. An Additional loxP site was inserted downstream of exon 4. Flp-mediated recombination removed the neomycin resistance cassette and left exons 3 and 4 floxed. Cre-mediated recombination removed exons 3 and 4. Western blot analysis confirmed the absence of protein expression in platelets.