The L1L2_Bact_P cassette was inserted at position 26246484 of Chromosome 2 upstream of exon 3 (Build GRCm39). The cassette is composed of an FRT site followed by lacZ sequence and a loxP site. This first loxP site is followed by neomycin resistance gene under the control of the human beta-actin promoter, SV40 polyA, a second FRT site and a second loxP site. A third loxP site is inserted downstream of exon 6 at position 26248459. A "conditional ready" (floxed) allele was created by flp recombinase expression in mice, with the deletion of the lacZ and neomycin sequences. Exons 3-6 are thus flanked by loxP sites. Further information on targeting strategies used for this and other IKMC alleles can be found at http://www.informatics.jax.org/mgihome/nomen/IKMC_schematics.shtml.