title: Impact of tamoxifen on adipocyte lineage tracing: Inducer of adipogenesis and prolonged nuclear translocation of Cre recombinase.
abstract: BACKGROUND
  The selective estrogen receptor modulator tamoxifen, in combination with the Cre-ER(T2) fusion protein, has been one of the mainstream methods to induce genetic recombination and has found widespread application in lineage tracing studies.
  
  
  RESULTS
  Here, we report that tamoxifen exposure at widely used concentrations remains detectable by mass-spectrometric analysis in adipose tissue after a washout period of 10 days. Surprisingly, its ability to maintain nuclear translocation of the Cre-ER(T2) protein is preserved beyond 2 months of washout. Tamoxifen treatment acutely leads to transient lipoatrophy, followed by de novo adipogenesis that reconstitutes the original fat mass. In addition, we find a "synthetically lethal" phenotype for adipocytes when tamoxifen treatment is combined with adipocyte-specific loss-of-function mutants, such as an adipocyte-specific PPARγ knockout. This is observed to a lesser extent when alternative inducible approaches are employed.
  
  
  CONCLUSIONS
  These findings highlight the potential for tamoxifen-induced adipogenesis, and the associated drawbacks of the use of tamoxifen in lineage tracing studies, explaining the discrepancy in lineage tracing results from different systems with temporal control of gene targeting.
authors.affiliation: Touchstone Diabetes Center, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Risheng
authors.initials: R
authors.lastname: Ye
authors.affiliation: Touchstone Diabetes Center, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Qiong A
authors.initials: QA
authors.lastname: Wang
authors.affiliation: Touchstone Diabetes Center, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Caroline
authors.initials: C
authors.lastname: Tao
authors.affiliation: Touchstone Diabetes Center, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Lavanya
authors.initials: L
authors.lastname: Vishvanath
authors.affiliation: Touchstone Diabetes Center, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Mengle
authors.initials: M
authors.lastname: Shao
authors.affiliation: Department of Molecular Genetics, The University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Jeffery G
authors.initials: JG
authors.lastname: McDonald
authors.affiliation: Touchstone Diabetes Center, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Rana K
authors.initials: RK
authors.lastname: Gupta
authors.affiliation: Touchstone Diabetes Center, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA ; Department of Cell Biology, The University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Philipp E
authors.initials: PE
authors.lastname: Scherer
keywords: Adipose tissue; Cre recombinase; Lineage tracing; Tamoxifen