The L1L2_gt2 cassette was inserted at position 113086383 of Chromosome 6 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 113088756. The critical exon(s) is/are thus flanked by loxP sites. The lacZ/neomycin sequence was removed via flp-mediated recombination generating a âconditional readyâ (floxed) allele.