A targeting vector is designed to insert a single loxP upstream of exon 1, and a loxP-flanked puromycin resistance (puro) cassette site downstream of exon 4 of the SIVA1, apoptosis-inducing factor (Siva1) gene. Cre-mediated recombination removed the floxed puro cassette leaving exons 1-4 floxed. (J:223572)