The L1L2_GT0_LF2A_LacZ_BetactP_neo cassette was inserted at position 161708956 of Chromosome X upstream of the critical exon 8 (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 8 at position 161710712. The critical exon 8 is thus flanked by loxP sites. The lacZ and neomycin resistance gene were removed via flp-mediated recombination. Exon 8 was deleted via cre-mediated recombination, generating a knock-out allele.