The L1L2_gt2 cassette was inserted at position 94778264 of Chromosome 8 upstream of the exon 4 (Build GRCm39). The cassette is composed of an FRT flanked lacZ/neomycin sequence followed by a loxP site. An additional loxP site is inserted downstream of exon 4 at position 94779080. Exon 4 is thus flanked by loxP sites. Flp mediated recombination removed the lacZ/neo cassette. Cre mediated recombination removed exon 4. (J:207410)