title: Balancer-Cre transgenic mouse germ cells direct the incomplete resolution of a tri-loxP-targeted Cyp1a1 allele, producing a conditional knockout allele.
abstract: To generate conditional alleles, genes are commonly engineered to contain recognition sites for bacteriophage recombinases, such as Cre recombinase. When such motifs (lox sites) flank essential gene sequences, and provided that Cre recombinase is expressed, Cre recombinase will excise the flanked sequence-creating a conditional knockout allele. Targeted conditional alleles contain a minimum of three lox sites. It would be desirable to have Cre recombinase perform partial resolution (i.e., recombination some of the time between only the two lox sites flanking the marker gene). Here we report use of the commercially available Balancer2-Cre transgenic mouse line to carry out this function from a tri-loxP-site-containing cytochrome p450 1A1 (Cyp1a1) targeted allele. Such incomplete resolution of this complex locus occurred progressively with age in germ cells of male mice; the conditional Cyp1a1 gene was recovered in offspring from mice containing the targeted Cyp1a1 allele and the Cre recombinase transgene. Removal of the marker gene resulted in a conditional Cyp1a1 allele whose expression was indistinguishable from that of the wild-type allele.
authors.affiliation: Department of Environmental Health and Center for Environmental Genetics (CEG), University of Cincinnati Medical Center, Cincinnati, OH, USA.
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Uno
authors.forename: Bin
authors.initials: B
authors.lastname: Wang
authors.forename: Howard G
authors.initials: HG
authors.lastname: Shertzer
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Nebert
authors.forename: Timothy P
authors.initials: TP
authors.lastname: Dalton
mesh_terms: D000483:Alleles; D000818:Animals; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics* / Q000378:metabolism*; D019020:Directed Molecular Evolution / Q000379:methods*; D015971:Gene Expression Regulation, Enzymologic; D018095:Germ-Line Mutation / Q000235:genetics*; D019426:Integrases / Q000235:genetics*; D008099:Liver / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D015202:Protein Engineering / Q000379:methods*; D011994:Recombinant Proteins; D011995:Recombination, Genetic / Q000235:genetics; D014764:Viral Proteins / Q000235:genetics*
chemical_list: D011994:Recombinant Proteins; D014764:Viral Proteins; D019363:Cytochrome P-450 CYP1A1; C045073:Cre recombinase; D019426:Integrases