Further Development 3.26: The CRE-LOX System

The Cre-lox technique for conditional mutagenesis, by which gene mutations can be generated in specific cells only. Mice are made wherein wild-type alleles (in this case, the genes encoding the Hnf4α transcription factor) have been replaced by alleles in which the second exon is flanked by loxP sequences. These mice are mated with mice having the gene for Cre-recombinase fused to a promoter that is active only in particular cells. In this case, the promoter is that of an albumin gene that functions early in liver development. In mice with both of these altered alleles, Cre-recombinase is made only in the cells where that promoter is activated (i.e., in the cells synthesizing albumin). The Cre-recombinase binds to the loxP sequences flanking exon 2 and removes that exon. Thus, in the case depicted here, only the developing liver cells lack a functional Hnf4α gene.

The Cre-lox technique for conditional mutagenesis, by which gene mutations can be generated in specific cells only. Mice are made wherein wild-type alleles (in this case, the genes encoding the Hnf4α transcription factor) have been replaced by alleles in which the second exon is flanked by loxP sequences. These mice are mated with mice having the gene for Cre-recombinase fused to a promoter that is active only in particular cells. In this case, the promoter is that of an albumin gene that functions early in liver development. In mice with both of these altered alleles, Cre-recombinase is made only in the cells where that promoter is activated (i.e., in the cells synthesizing albumin). The Cre-recombinase binds to the loxP sequences flanking exon 2 and removes that exon. Thus, in the case depicted here, only the developing liver cells lack a functional Hnf4α gene.

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