The L1L2_Bact_P cassette was inserted at position 115707390 of Chromosome 11 upstream of exon 6 (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 a 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 exon 6 at position 115708216. Exon 6 is thus flanked by loxP sites. Subsequent cre-mediated recombination resulted in this reporter knockout allele.