The L1L2_Bact_P cassette was inserted at position 82189400 of Chromosome 15 upstream of the critical exons 2 through 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 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 2 through 4 at position 82191234. The critical exon 2 through 4 are thus flanked by loxP sites. Cre-mediated recombination removed the selection cassette and exons 2 through 4. Western blot analysis confirmed the absence of protein expression in testes. (J:227499)