The L1L2_gt1 cassette was inserted at position 34700726 of Chromosome 2 upstream of the critical exon(s) (Build GRCm39). The cassette is composed of an FRT flanked lacZ/neomycin sequence followed by a loxP site. An additional loxP site is inserted downstream of the targeted exon(s) at position 34701600. The critical exon(s) is/are thus flanked by loxP sites. A null/knockout allele was created by flp and cre recombinase expression in mice carrying this allele to remove the lacZ sequence, neo selection cassette and the 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