Biochemical and Biophysical Research Communications
Balancer-Cre transgenic mouse germ cells direct the incomplete resolution of a tri-loxP-targeted Cyp1a1 allele, producing a conditional knockout allele
Section snippets
Materials and methods
Mice. Balancer2-Cre transgenic mice, having the strain name TgN(balancer2)3Cgn, were purchased from The Jackson Laboratory (Bar Harbor, ME). Generation of the conditional Cyp1a1 knockout mouse strain has been previously described [13]. All experiments involving mice were conducted in accordance with the National Institutes of Health (NIH) standards for the care and use of experimental animals and the University of Cincinnati Institutional Animal Care and Use Committee.
DNA preparations. DNA for
Importance of CYP1A1 in toxicity and carcinogenesis
CYP1A1 is one of the three members of the mammalian CYP1 family, which includes CYP1A1, CYP1A2, and CYP1B1 [25]. The CYP1A1 gene is highly inducible at the level of transcription, the up-regulation being controlled by the aromatic hydrocarbon receptor (AHR). Translocation of the cytoplasmic AHR, to become a nuclear transcriptional activator, occurs as the result of ligand binding. Ligands for the AHR include numerous planar foreign chemicals and, in general, AHR ligands are metabolized by
Conclusions
The Nes/Cre transgene present in the bal2Cre line of transgenic mice has been used by others to bypass embryonic lethality associated with essential conditional floxed alleles [22]. This result reflects a mosaic pattern of Cre-mediated recombination in tissues—some cells showing recombination, others not. This mosaic pattern is the result of threshold expression of Cre recombinase such that incomplete resolution of loci containing three or more lox sites may be observed and inherited. One
Acknowledgements
We thank our colleagues for many fruitful discussions and a careful reading of the manuscript. This work was supported, in part, by NIH Grants R01 ES08147 and P30 ES06096.
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Present address: Department of Biochemistry, Nihon University School of Medicine, 30-1 Oyaguchikami-cho, Itabashi-ku, Tokyo 173-8610, Japan.