The L1L2_Bact_P cassette was inserted at position 21757262 of Chromosome 18 upstream of the critical 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 the targeted exon 3 at position 21759352. Cre-mediated recombination removed exon 3 and the selection cassette leaving behind the reporter cassette. (J:263511)