Tetracycline response element driven Cre causes ectopic recombinase activity independent of transactivator element

Objective: Tamoxifen is widely used for inducible Cre-LoxP systems but has several undesirable side effects for researchers investigating metabolism or energy balance, including weight loss, lipoatrophy, and drug incorporation into lipid stores. For this reason, we sought to determine whether a doxycycline-inducible system would be more advantageous for adipocyte-specific Cre mouse models, but serendipitously discovered widespread ectopic tetracycline response element Cre (TRE-Cre) recombinase activity.Methods: Adipocyte-specific tamoxifen-and doxycycline-inducible Cre mice were crossed to fluorescent Cre reporter mice and visualized by confocal microscopy to assess efficiency and background activity. TRE-Cre mice were crossed to stop-floxed diphtheria toxin mice to selectively ablate cells with background Cre activity.Results: Tamoxifen-and doxycycline-inducible systems performed similarly in adipose tissues, but ectopic Cre recombination was evident in numerous other cell types of the latter, most notably neurons. The source of ectopic Cre activity was isolated to the TRE-Cre transgene, driven by the pTet (tetO7) tetracycline-inducible promoter. Ablation of cells with ectopic recombination in mice led to stunted growth, diminished survival, and reduced brain mass.Conclusions: These results indicate that tamoxifen-and doxycycline-inducible adipocyte-specific Cre mouse models are similarly effi-cient, but the TRE-Cre component of the latter is inherently leaky. TRE-Cre background activity is especially pronounced in the brain and peripheral nerve fibers, and selective ablation of these cells impairs mouse development and survival. Caution should be taken when pairing TRE-Cre with floxed alleles that have defined roles in neural function, and additional controls should be included when using this model system.(c) 2022 The Author(s). Published by Elsevier GmbH. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

This study compared the effects of tamoxifen and doxycycline induction on adipocyte-specific Cre mouse models. The study found that the doxycycline-inducible system had significant ectopic Cre recombination activity, especially in neurons. This ectopic Cre activity was generated by the TRE-Cre transgene, which exhibited pronounced background activity in the brain and peripheral nerve fibers. Selective ablation of these cells had implications for mouse development and survival.