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

Geroscience. 2019 Oct;41(5):691-708. doi: 10.1007/s11357-019-00090-2. Epub 2019 Sep 7.


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: Cortex; Epigenome; Hippocampus; Methylation; Retina; Sex differences; Tamoxifen; Transcriptome; Transgenic.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Cerebral Cortex / metabolism
  • Cytoskeletal Proteins / genetics
  • Cytoskeletal Proteins / metabolism
  • DEAD-box RNA Helicases / genetics
  • DEAD-box RNA Helicases / metabolism
  • DNA / metabolism
  • DNA Methylation
  • Early Growth Response Protein 2 / genetics
  • Early Growth Response Protein 2 / metabolism
  • Epigenome
  • Female
  • Gene Expression
  • Hippocampus / metabolism
  • Histone Demethylases / genetics
  • Histone Demethylases / metabolism
  • Integrases / drug effects*
  • Male
  • Mice, Inbred C57BL
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism
  • Proto-Oncogene Proteins c-fos / genetics
  • Proto-Oncogene Proteins c-fos / metabolism
  • RNA / metabolism
  • RNA, Long Noncoding / genetics
  • RNA, Long Noncoding / metabolism
  • Retina / metabolism
  • Tamoxifen / pharmacology*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transcriptome


  • Cytoskeletal Proteins
  • Early Growth Response Protein 2
  • Egr2 protein, mouse
  • Eif2s3y protein, mouse
  • Fos protein, mouse
  • Nerve Tissue Proteins
  • Proto-Oncogene Proteins c-fos
  • RNA, Long Noncoding
  • Transcription Factors
  • XIST non-coding RNA
  • activity regulated cytoskeletal-associated protein
  • Tamoxifen
  • RNA
  • DNA
  • Histone Demethylases
  • Utx protein, mouse
  • Cre recombinase
  • Integrases
  • DEAD-box RNA Helicases
  • Ddx3x protein, mouse