The L1L2_gt1 cassette was inserted at position 62647276 of Chromosome 16 upstream of the critical exon (exon 3) (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 exon 3 at position 62648425. A "conditional ready" (floxed) allele was created by flp recombinase expression in mice carrying this allele to remove the lacZ sequence and neo selection cassette, leaving exon 3 flanked by loxP sites. (J:240795)