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ISSN 1672-9145 Acta Biochim Biophys Sin 2005, 37(2): 133–138 CN 31-1940/Q

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Temporal Control of Cre Recombinase-mediated in Vitro DNA Recombination by Tet-on Gene Expression System

Zhong-Min GUO, Kang XU¹, Ying YUE, Bing HUANG, Xin-Yan DENG, Nü-Qi ZHONG, Xun HONG, Xi-Gu CHEN*, and Dong XIAO*

Center of Experimental Animals, Sun Yat-Sen (Zhongshan) University, Guangzhou 510080, China;

¹The First Affiliated Hospital of Sun Yat-Sen University, Sun Yat-Sen University, Guangzhou 510080, China

Abstract Conditional gene expression and gene deletion are important experimental approaches for examining the functions of particular gene products in mouse models. These strategies exploiting Cre-mediated site-specific DNA recombination have been incorporated into transgenic and gene-targeting procedures to allow in vivo manipulation of DNA in embryonic stem cells (ES cells) or living animals. The Cre/lox P system has become widely used in conditional gene targeting, conditional gene repair and activation, inducible chromosome translocation, and chromosome engineering. In this project, we have employed the universal transgenic system and the liver-specific promoter system for tightly temporal and liver-specific control of Cre gene expression in mice that (1) integrates the advantages of the Tet-on gene expression system and Cre/lox P site-mediated gene activation, and (2) simplifies the scheme of animal crosses through a combination of two control elements in a single transgene. A liver-specific apoE promoter was inserted into the promoter cloning site upstream of the rtTA cassette of pCore construct to generate the transgene construct pApoErtTA-tetO-Cre, followed by demonstrating stringent regulation of doxycycline (Dox)-induced Cre-mediated recombination in the lox P-flanked transcription STOP cassette-modified BEL-7402 cells. That is to say, in the absence of Dox, the Cre gene is not expressed and will not induce site-specific recombination between two lox P sites, whereas on exposure to Dox, the Cre gene will be expressed and the recombination will occur. Together, these data indicate that the Tet-on gene expression system is able to successfully and stringently control Cre expression in vitro, which lays a solid foundation for efficient and spatio-temporal Cre gene activation in transgenic mice.

Key words conditional gene regulation; Cre recombinase; human apolipoprotein E gene (apoE) promoter; Tet-on gene expression system; universal transgenic system

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Received: July 12, 2004 Accepted: December 22, 2004

This work was supported by the grants from the National Natural Science Foundation of China (No. 30271177 and No. 39870676), the Natural Science Foundation of Guangdong Province (No. 021903), and the Postdoctoral Fellowship Foundation of China (Series 29)

*Corresponding authors: Tel, 86-20-87330450/87331393; Fax, 86-20-87331230; E-mail, [email protected] & [email protected]