Cyp1a^tm1Dwn

The Cyp1a2(t) targeted allele (J:122409) was generated using a targeting vector designed to insert a loxP-flanked PGK-NEO cassette 350 bp downstream of the endogenous stop codon (about 60 bp 3' of exon 7). The construct was electroporated into 129S6/SvEvTac-derived embryonic stem (ES) cells which were microinjection into C57BL/6 blastocysts. The chimeras were bred with C57BL/6 to generate Cyp1a2(t) mutant mice. To create the Cyp1a1 targeted allele (J:59398), a targeting vector was designed to insert a loxP-flanked hypoxanthine phosphoribosyltransferase (HPRT) minigene in intron 1 and a loxP site downstream of the termination codon in exon 7. Following electroporation into E14TG2a (HPRT-) ES cells and ES cell microinjection into the blastocoele cavity of C57BL/6J embryos, chimeric males were bred with C57BL/6J females. As described in J:86748, these Cyp1a1(t) mutant mice were then bred to a Cre-deleter strain (CAGGS-CRE, mixed C57BL/6J and FVB/NJ genetic background). The resulting transgenic mice found to be heterozygous for the floxed null Cyp1a1(-) allele (containing only exon 1, a portion of intron 1, and one remaining loxP site in the 3' UTR) were bred to mice heterozygous for the Cyp1a2(t) allele (as described in J:122409). Mutant mice (Cyp1a2(t), Cyp1a1(-), CAGGS-CRE) were bred to C57BL/6. Because of the close genomic position of these two genes, offspring having undergone Cre recombinase-mediated interchromosomal recombination between the loxP sites 3' beyond the stop codons of the Cyp1a2 and Cyp1a1 genes could be selected. Such mice were backcrossed to C57BL/6 for 10 generations (while selecting against the Cre-deleter transgene) to generate Cyp1a1/1a2 mutant mice. (J:59398, J:86748, J:122409)