The L1L2_Bact_P cassette was inserted at position 25644591 of Chromosome 14 upstream of exon 9 (Build GRCm39). The cassette is composed of an FRT site followed by lacZ sequence and a loxP site. This first loxP site is followed by neomycin resistance gene under the control of the human beta-actin promoter, SV40 polyA, a second FRT site and a second loxP site. A third loxP site is inserted downstream of the exon 9 at position 25645559. A "conditional ready" (floxed) allele was created by flp recombinase expression in mice, resulting in the deletion of the lacZ sequence and neomycin selection cassette. The exon 9 remains flanked by loxP sites.