The L1L2_Bact_P cassette was inserted at position 3933594 of Chromosome 10 upstream of the critical exon 5 (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 the targeted exon(s) at position 3934442. The critical exon(s) is/are thus flanked by loxP sites. Cre mediated recombination removed the neo cassette and exon 5 creating a reporter allele. RT-PCR and immunoblot analysis confirmed the absence of transcript and full length protein, respectively, in homozygous embryos. LacZ expression partially recapitulates endogenous gene expression. 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