Smooth muscle protein 22 alpha-Cre is expressed in myeloid cells in mice

Zhuxia Shen, Chao Li, Ryan A. Frieler, Alena S. Gerasimova, Soo Jung Lee, Jing Wu, Michael M. Wang, Carey N. Lumeng, Frank C. Brosius, Sheng Zhong Duan, Richard M. Mortensen

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


Background: Experiments using Cre recombinase to study smooth muscle specific functions rely on strict specificity of Cre transgene expression. Therefore, accurate determination of Cre activity is critical to the interpretation of experiments using smooth muscle specific Cre. Methods and results: Two lines of smooth muscle protein 22 α-Cre (SM22α-Cre) mice were bred to floxed mice in order to define Cre transgene expression. Southern blotting demonstrated that SM22α-Cre was expressed not only in tissues abundant of smooth muscle, but also in spleen, which consists largely of immune cells including myeloid and lymphoid cells. PCR detected SM22α-Cre expression in peripheral blood and peritoneal macrophages. Analysis of SM22α-Cre mice crossed with a recombination detector GFP mouse revealed GFP expression, and hence recombination, in circulating neutrophils and monocytes by flow cytometry. Conclusions: SM22α-Cre mediates recombination not only in smooth muscle cells, but also in myeloid cells including neutrophils, monocytes, and macrophages. Given the known contributions of myeloid cells to cardiovascular phenotypes, caution should be taken when interpreting data using SM22α-Cre mice to investigate smooth muscle specific functions. Strategies such as bone marrow transplantation may be necessary when SM22α-Cre is used to differentiate the contribution of smooth muscle cells versus myeloid cells to observed phenotypes.

Original languageEnglish (US)
Pages (from-to)639-642
Number of pages4
JournalBiochemical and Biophysical Research Communications
Issue number4
StatePublished - Jun 15 2012
Externally publishedYes


  • Macrophages
  • Monocytes
  • Myeloid cells
  • Neutrophils
  • SM22α-Cre
  • Smooth muscle cells

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology


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