The L1L2_Bact_P cassette was inserted upstream of exon 2 (Build GRCm38). The L1L2_Bact_P cassette was composed of an FRT site, a mouse En2 intron/splice-acceptor/exon (En2 SA), an IRES enhancer, the beta-galactosidase gene (lacZ), an SV40 polyadenylation signal (SV40pA), a loxP site, a human beta-actin promoter (hbactP), the neomycin-resistance gene (neo), a second SV40 polyadenylation signal (SV40pA), a second FRT site, and a second loxP site. A third loxP site was inserted downstream of exon 2. KOMP vector PG00052_Z_4_A06 was used. (J:280699)