The L1L2_gt2 cassette was inserted at position 113293068 of Chromosome 6 upstream of the critical exons 4 through 6 (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 exons 4-6 at position 113294936. The critical exons 4 through 6 are thus flanked by loxP sites. Cre-mediated recombination removed exons 4-6 and left the FRT flanked lacZ/neomycin sequence followed by one loxP site. 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.