Schematic of Lman1 mutant alleles. (A) Lman1^gt1 allele carries a gene trap insertion in intron 10.²⁸  (B) The Lman1 conditional gene trap allele (Lman1^cgt) contains a gene trap insertion in intron 1 flanked by 2 FRT sites. Mice carrying this allele were crossed to β-actin FLP transgenic mice.⁵  Mice heterozygous for the resulting Lman1 “floxed” allele (Lman1^fl/+) (C) were crossed to EIIA-Cre⁺ transgenic mice to excise exons 2 and 3, generating the Lman1 null allele (Lman1^–) (D). Gray blocks represent exons. A, B, and C represent genotyping primers. (E) A 3-primer PCR assay (primers A, B, and C) distinguishes the Lman1⁺ (444 bp), Lman1^cgt (508 bp), and Lman1^– (635 bp) alleles. The Lman1^fl allele (not shown in this image) also generates the same PCR product band as the Lman1^cgt allele. βact:neo, human β-actin promoter-driven neomycin cassette; β-Geo, β-galactosidase-neo fusion; cgt, conditional gene trap; En2 SA, splice acceptor of mouse En2 exon 2; fl, floxed; IRES, encephalomyocarditis virus (EMCV) internal ribosomal entry site; lacZ, Escherichia coli β-galactosidase gene; pA, poly-adenylation signal; SA, splice acceptor cassette.