Submitted on July 3, 2008
Accepted on July 7, 2008
Germ Line Activation of the Tie2 and SMMHC Promoters Causes Non-Cell Specific Deletion of Floxed Alleles
Willem J de Lange1, Carmen M Halabi1, Andreas M Beyer1, and Curt D. Sigmund2*
1 University of Iowa
2 University of Iowa College of Medicine
* To whom correspondence should be addressed. E-mail: curt-sigmund{at}uiowa.edu.
Tissue-specific knockouts generated through Cre-loxP recombination have become an important tool to manipulate the mouse genome. Normally, two successive rounds of breeding are performed to generate mice carrying two floxed target-gene alleles and a transgene expressing Cre-recombinase tissue-specifically. We show herein that two promoters commonly used to generate endothelial-specific (Tie2) and smooth muscle-specific (smooth muscle myosin heavy chain, Smmhc) knockout mice, exhibit activity in the female and male germ lines, respectively. This can result in the inheritance of a null allele in the second generation which is not tissue-specific. Careful experimental design is required therefore to ensure that tissue-specific knockouts are indeed tissue-specific and that appropriate controls are used to compare strains.
