The L1L2_Bact_P cassette was inserted at position 124672980 of Chromosome 8 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 is followed by a 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 124673825. The critical exon(s) is/are thus flanked by loxP sites. A null/knockout allele was created by cre recombinase expression in mice carrying the tm1a allele to remove the neo selection cassette and loxP-flanked critical exon(s). 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