The insertion of the L1L2_Bact_P cassette created a deletion of size 1163 starting at position 55468110 and ending at position 55469273 of Chromosome 13 (Genome Build GRCm39). This deletion results in the removal of functionally critical exon(s). The cassette is composed of an FRT site followed by lacZ sequence and a loxP site. This first loxP site was followed by a neomycin selection cassette under the control of the human beta-actin promoter, SV40 polyA, a second FRT site and a second loxP site. Cre expression excised the neomycin selection cassette.