The L1L2_Bact_P cassette was inserted at position 25287449 of Chromosome 7. 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 inserted into intron 8. A third loxP site is inserted in intron 11. Flp-mediated recombination removed the FRT-flanked neo cassette leaving exons 9 to 11 floxed.