Cre & Reporter Mice

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Featured Cre & Reporter Mouse Models

Explore Cre driver and reporter mouse strains for conditional gene targeting, tissue-specific recombination, lineage tracing, cell labeling, and gene expression studies.

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Cre & Reporter Mouse Models

Search available Cre, inducible Cre, and reporter mouse strains for conditional gene targeting, tissue-specific recombination, lineage tracing, and other genetic research applications.

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Cre & Reporter Mice FAQ

Frequently Asked Questions About Cre & Reporter Mice

What are the differences among Cre, iCre, CreERT2, and MerCreMer?

Cre (Cyclization Recombination Enzyme) is an enzyme protein derived from bacteriophage P1, with a molecular weight of approximately 38 kDa. It can recognize and catalyze homologous recombination between two LoxP sites, resulting in phenomena such as DNA deletion, inversion, and translocation. The Cre-loxp system is widely used in the generation of conditional knockout or conditional overexpression animal models. iCre refers to Codon-improved Cre recombinase, which enhances the in vivo expression efficiency of Cre through codon optimization. Inducible Cre generally refers to CreER, a protein expressed by fusing a mutant of the ligand-binding domain of the estrogen receptor (ER) with Cre recombinase. CreERT2 is more sensitive and efficient than CreER. In the absence of Tamoxifen, Cre-ERT2 resides in the cytoplasm and cannot enter the nucleus; when induced by Tamoxifen, the metabolite 4-0HT (an estrogen analog) of Tamoxifen binds to ER, exposing the nuclear localization signal of ER. Guided by the nuclear localization signal, Cre recombinase can enter the nucleus and perform its function. Thus, by controlling the injection time of estrogen, time-specific regulation of gene recombination can be achieved. MerCreMer consists of Cre recombinase flanked by a mutated mouse estrogen receptor (Mer) ligand-binding domain (amino acids 281-599, G525R) on each side, which can reduce the probability of entering the nucleus without drug treatment and avoid premature leakage 1.

How does Cre expressed in the reproductive system interact with a floxed allele?

When a Cre-expressing mouse is crossed with a floxed mouse, the resulting offspring that are positive for both the Cre transgene and the floxed allele (with the floxed allele generally maintained in the homozygous state) express Cre recombinase in the cells where the Cre driver is active. Cre recognizes the loxP sites in the same orientation and excises the DNA sequence between them. This recombination event generates a loss-of-function allele, resulting in conditional knockout of the target gene in Cre-expressing cells. Consequently, the target gene is selectively inactivated in the relevant tissues or organs.

How can Cre tissue-specific expression be confirmed?

When conducting relevant research using Cre strains, Cre tissue expression can typically be evaluated using the following approaches: ① Query the references of the relevant strains; ② Query the Cre expression information induced by various promoters through MGI-Recombinase(Cre) Activity. If Cre is expressed in early embryos, the reproductive system, or widely throughout the body, then after breeding with flox strains, mice with systemic knockout of the flox gene may be directly obtained; ③ When the Cre used has no such reference information, the strain can be bred with Tool mice carrying a fluorescent reporter gene, and the applicability of Cre mice can be judged by observing the expression of the reporter gene in double-positive offspring. In addition, Cre strains driven by specific promoters may also have Cre activity in non-target tissues, and special attention needs to be paid to the leaky expression of Cre in the reproductive system. If there is leaky expression, it may prevent us from obtaining fl/fl;T mice, and the offspring may exhibit phenotypes related to systemic gene knockout. For example, the Prrx1 (paired related homeobox 1) promoter is expected to drive Cre expression in early limb buds and craniofacial regions, but staining results show that this Cre is also active in some oocytes in females and some interstitial cells in males. Therefore, to minimize the impact of leaky expression of Cre in the reproductive system, male Cre mice can be selected to breed with female flox mice, and mice with null bands can be excluded.

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