The floxed exon 3 in Ikbkbtm2Mka was removed via cre-mediated recombination by breeding with Tg(Vil-cre)1Mka mice. Although this cre transgene is expressed in the small intestinal epithelial and colon epithelial cells, a small amount of cre recombination occurred in the testis resulting in germline transmission of the exon 3 deleted allele.