The L1L2_Bact_P cassette was inserted at position 78752068 of Chromosome 14 upstream of the critical exon(s) (Build GRCm39). The cassette is composed of an FRT site followed by lacZ sequence and a loxP site. This first loxP site was 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 was inserted downstream of the targeted exon(s) at position 78752841. The critical exon(s) were thus flanked by loxP sites, and subsequent Cre-mediated excistion deleted the critical sequence and the neomycin selection cassette yielding a reporter knockout allele. 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.