The L1L2_Bact_P cassette was inserted at position 56681275 of Chromosome 18 upstream of the critical exon(s) (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(s) at position 56682076. The critical exon 6 is thus flanked by loxP sites. Flp-mediated recombination removed the lacZ and neomycin resistance gene and subsequent cre-mediated recombination deleted exon 6 generating a knockout mouse. Western blot analysis of brain and kidney confirmed absence of protein in homozygotes.