The L1L2_Bact_P cassette was inserted at position 164405575 of Chromosome 2 upstream of the critical exons 3 and 4 (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 exons at position 164408134. The critical exons 3 and 4 are thus flanked by loxP sites. Cre-mediated recombination removed the drug resistance gene and exons 3 and 4, generating a reporter knockout mouse.