This allele was created by crossing mice heterozygous for both F2rtm2Cgh and F2rl1tm2Cgh to mice expressing a beta actin cre. The resulting allele has the entire region from the hygro selection cassette in exon 1 of F2rtm2Cgh through the neomycin selection cassette of F2rl1tm2Cgh excised. LacZ remains in the hybrid exon 1 that results. (J:157446)