The L1L2_Bact_P cassette was inserted at position 106767151 of Chromosome 9 upstream of exon 3 (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 3 at position 106767840. A "conditional ready" (floxed) allele was created through flp-mediate recombination, leaving exon 3 floxed. (J:211812)