© 2005 American Heart Association, Inc.
Letters to the Editor |
Regulated Transgene Expression in Vascular Smooth Muscle
Gladstone Institute of Cardiovascular Disease, University of California, San Francisco
Department of Medicine, University of Washington, Seattle
An extract of the first 250 words of the full text is provided, because this article has no abstract. |
To the Editor:
We are writing in reference to 2 articles published in Circulation Research, both of which report use of transgenic mice with smooth muscle cell–specific expression of the tetracycline-regulated transactivator (tTA) to activate conditional tTA-regulated alleles in the vasculature of transgenic mice.1,2 The purpose of this letter is to report our experience with these mice and to inform the readership that, in our hands, these mice show no evidence of either (1) an ability to transactivate conditional alleles or (2) expression of the tTA in vascular tissue.
Generation of mice in which a fragment of the murine SM22
promoter was used to achieve smooth muscle–specific expression of the tTA was first reported in abstract form in 1997 by Husain et al.3 In 1998, experimental results obtained with these mice appeared in a figure contributed by Dr Husain to a review article in Circulation Research.4 This figure depicted doubly transgenic SM22-tTA/tetO-ß-galactosidase (ß-gal) embryos and aortas harvested from adult doubly transgenic SM22-tTA/tetO-ß-gal mice. Incubation of the embryos with X-gal chromogen showed doxycycline-suppressible ß-gal expression primarily in the heart and somites, with apparent faint staining in the vasculature. The X-gal–stained aortas showed sparse ß-gal expression which was "inhibited" by doxycycline treatment.
Based on these reports, we requested these transgenic SM22-tTA mice for use in our own investigations. In 1999 Dr. Husain kindly sent us transgenic SM22-tTA mice derived from 2 independent lines. We were particularly appreciative of this generosity because at this time the SM22