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Tamoxifen induction of Cre recombinase does not cause long-lasting or sexually divergent responses in the CNS epigenome or transcriptome: implications for the design of aging studies

  • Ana J. Chucair-Elliott
  • Sarah R. Ocanas
  • David R. Stanford
  • Niran Hadad
  • Benjamin Wronowski
  • Laura Otalora
  • Michael B. Stout
  • Willard M. FreemanEmail author
Original Article

Abstract

The systemic delivery of tamoxifen (Tam) to activate inducible CreERT2-loxP transgenic mouse systems is now widely used in neuroscience studies. This critical technological advancement allows temporal control of DNA-cre recombination, avoidance of embryonically lethal phenotypes, and minimization of residual cell labeling encountered in constitutively active drivers. Despite its advantages, the use of Tam has the potential to cause long-lasting, uncharacterized side effects on the transcriptome and epigenome in the CNS, given its mixed estrogen receptor (ER) agonist/antagonist actions. With the welcome focus on including both sexes in biomedical studies and efforts to understand sex differences, Tam administration could also cause sexually divergent responses that would confound studies. To examine these issues, epigenetic and transcriptomic profiles were compared in C57BL/6 J female and male hippocampus, cortex, and retina 1 month after a 5-day Tam treatment typical for cre induction, or vehicle control (sunflower seed oil). Cytosine methylation and hydroxymethylation levels, in both CG and non-CG contexts, were unchanged as determined by oxidative bisulfite sequencing. Long-lasting Tam transcriptomic effects were also not evident/minimal. Furthermore, there is no evidence of sexually divergent responses with Tam administration and Tam did not alter sex differences evident in controls. Combined with recently reported data that Tam alone does not cause long-lasting changes in behavior and neurogenesis, our findings provide confidence that Tam can be used as a cre-recombinase inducer without introducing significant confounds in transcriptomic and epigenomic neuroscience studies, particularly those focused on genomic and transcriptomic aspects of the aging brain.

Keywords

Transgenic Tamoxifen Sex differences Epigenome Methylation Transcriptome Hippocampus Cortex Retina 

Notes

Acknowledgements

The authors acknowledge the Laboratory for Molecular Biology and Cytometry Research at OUHSC for the use of the Core Facility which provided Illumina MiSeq Next Generation Sequencing services and the Oklahoma Medical Research Foundation Clinical Genomics Center which provided NextSeq services Computing for this project was performed at the OU Supercomputing Center for Education and Research (OSCER) at the University of Oklahoma (OU).

Support

This work was supported by grants from the National Institutes of Health (NIH) P30AG050911, R56AG059430, R01AG58430, P20GM125528, R01AG0256161, Veterans Affairs I01BX003906, Oklahoma Center for Adult Stem Cell Research (OCASCR) grant through the Oklahoma Tobacco Settlement Endowment Trust, and Presbyterian Health Foundation.

Supplementary material

11357_2019_90_MOESM1_ESM.docx (517 kb)
ESM 1 (DOCX 516 kb).

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Copyright information

© This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply 2019

Authors and Affiliations

  • Ana J. Chucair-Elliott
    • 1
    • 2
  • Sarah R. Ocanas
    • 1
    • 2
  • David R. Stanford
    • 1
    • 2
  • Niran Hadad
    • 1
    • 3
    • 4
  • Benjamin Wronowski
    • 1
  • Laura Otalora
    • 1
    • 2
  • Michael B. Stout
    • 1
    • 5
  • Willard M. Freeman
    • 1
    • 2
    • 3
    • 4
    • 6
    Email author
  1. 1.Reynolds Oklahoma Center on AgingUniversity of Oklahoma Health Sciences CenterOklahoma CityUSA
  2. 2.Department of PhysiologyUniversity of Oklahoma Health Sciences CenterOklahoma CityUSA
  3. 3.Oklahoma Nathan Shock Center for AgingUniversity of Oklahoma Health Sciences CenterOklahoma CityUSA
  4. 4.Oklahoma Center for NeuroscienceUniversity of Oklahoma Health Sciences CenterOklahoma CityUSA
  5. 5.Department of Nutritional SciencesUniversity of Oklahoma Health Sciences CenterOklahoma CityUSA
  6. 6.Oklahoma City Veterans Affairs Medical CenterOklahoma CityUSA

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