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Warning regarding hematological toxicity of tamoxifen activated CreERT2 in young Rosa26CreERT2 mice
Martina Rossi1, Aude Salomon1, Nicolas Chaumontel1
1Laboratory BioSanté U1292, Univ. Grenoble Alpes, INSERM, CEA, 38000, Grenoble, France.
Abstract:
The Cre-lox system is a versatile and powerful tool used in mouse genetics. It allows spatial and/or temporal control of the deletion of a target gene. The Rosa26-CreERT2 (R26CreERT2) mouse model allows ubiquitous expression of CreERT2. Once activated by tamoxifen, CreERT2 will enter into the nuclei and delete floxed DNA sequences. Here, we show that intraperitoneal injection of tamoxifen in young R26CreERT2 mice leads to morbidity and mortality within 10 days after the first injection, in the absence of a floxed allele. Activation of CreERT2 by tamoxifen led to severe hematological defects, with anemia and a strong disorganization of the bone marrow vascular bed. Cell proliferation was significantly reduced in the bone marrow and the spleen resulting in the depletion of several hematopoietic cells. However, not all cell types or organs were affected to the same extent. We realized that many research groups are not aware of the potential toxicity of Cre recombinases, resulting in misinterpretation of the observed phenotype and in a waste of time and resources. We discuss the necessity to include tamoxifen injected CreERT2 controls lacking a floxed allele in experimental designs and to improve communication about the limitations of Cre-lox mouse models among the scientific community.
Insights
Tamoxifen activation of Cre-lox systems in Rosa26-CreERT2 mice causes severe toxicity and death, even without a floxed allele. Researchers must use proper controls to avoid misinterpreting Cre recombinase toxicity in mouse genetics studies.
Area of Science:
- Genetics
- Molecular Biology
- Toxicology
Background:
- The Cre-lox system enables targeted gene deletion in mouse models.
- Rosa26-CreERT2 mice express CreERT2 ubiquitously, activated by tamoxifen.
- Tamoxifen administration leads to CreERT2 nuclear translocation and DNA recombination.
Purpose of the Study:
- To investigate the toxicity of tamoxifen-induced CreERT2 activation in Rosa26-CreERT2 mice.
- To identify potential adverse effects and hematological defects.
- To highlight the importance of appropriate controls in Cre-lox studies.
Main Methods:
- Intraperitoneal injection of tamoxifen in young R26CreERT2 mice.
- Assessment of morbidity and mortality within 10 days.
- Analysis of hematological parameters, bone marrow, and spleen.
Main Results:
- Tamoxifen induced significant morbidity and mortality in R26CreERT2 mice lacking floxed alleles.
- Severe anemia and bone marrow vascular disorganization were observed.
- Reduced cell proliferation in bone marrow and spleen led to hematopoietic cell depletion.
Conclusions:
- Tamoxifen-induced CreERT2 activation exhibits inherent toxicity, independent of gene deletion.
- Uncontrolled CreERT2 activation can cause severe hematological defects and lethality.
- Experimental designs must include tamoxifen-injected CreERT2 controls without floxed alleles to accurately interpret phenotypes and avoid resource waste.
