The L1L2_gt1 cassette was inserted at position 89616630 of Chromosome 7 upstream of the exon 7 (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 exon 7 at position 89617432. Exon 7 was thus flanked by loxP sites. A "conditional ready" (floxed) allele was created by flp mediated recombination. Cre-mediated recombination removed the floxed exon. 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. (J:275851)