A targeting vector was constructed with the nls-cre recombinase sequence fused to exon 1 of the Ptgds locus and a poly A signal with a floxed EGFP-hygromycin selection cassette 3' to the cre poly A signal. Homologous recombination in ES cells was performed to replace exon 1 with the targeting construct. Chimeras were crossed with FVB/N mice. The floxed selection cassette was excised by crossing offspring to the Tg(EIIa-cre)C5379Lmgd deletor line and the EIIa transgene was bred from the background. (J:173718)