Int J Biol Sci 2009; 5(2):171-181. doi:10.7150/ijbs.5.171 This issue

Research Paper

Developing tTA Transgenic Rats for Inducible and Reversible Gene Expression

Hongxia Zhou1, Cao Huang1, Min Yang1, Carlisle P Landel2, Pedro Yuxing Xia3, Yong-Jian Liu4, Xu Gang Xia1 ✉

1. Department of Pathology, Anatomy & Cell Biology;
2. Department of Microbiology; Thomas Jefferson University, 1020 Locust Avenue, Philadelphia, PA 19107, USA
3. A volunteer student of Lower Merion High School, PA, USA
4. Department of Neurobiology, University of Pittsburgh, Pittsburgh, USA

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Zhou H, Huang C, Yang M, Landel CP, Xia PY, Liu YJ, Xia XG. Developing tTA Transgenic Rats for Inducible and Reversible Gene Expression. Int J Biol Sci 2009; 5(2):171-181. doi:10.7150/ijbs.5.171. Available from

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To develop transgenic lines for conditional expression of desired genes in rats, we generated several lines of the transgenic rats carrying the tetracycline-controlled transactivator (tTA) gene. Using a vigorous, ubiquitous promoter to drive the tTA transgene, we obtained widespread expression of tTA in various tissues. Expression of tTA was sufficient to strongly activate its reporter gene, but was below the toxicity threshold. We examined the dynamics of Doxycycline (Dox)-regulated gene expression in transgenic rats. In the two transmittable lines, tTA-mediated activation of the reporter gene was fully subject to regulation by Dox. Dox dose-dependently suppressed tTA-activated gene expression. The washout time for the effects of Dox was dose-dependent. We tested a complex regime of Dox administration to determine the optimal effectiveness and washout duration. Dox was administered at a high dose (500 μg/ml in drinking water) for two days to reach the effective concentration, and then was given at a low dose (20 μg/ml) to maintain effectiveness. This regimen of Dox administration can achieve a quick switch between ON and OFF statuses of tTA-activated gene expression. In addition, administration of Dox to pregnant rats fully suppressed postnatal tTA-activated gene expression in their offspring. Sufficient levels of Dox are present in mother's milk to produce maximal efficacy in nursing neonates. Administration of Dox to pregnant or nursing rats can provide a continual suppression of tTA-dependent gene expression during embryonic and postnatal development. The tTA transgenic rat allows for inducible and reversible gene expression in the rat; this important tool will be valuable in the development of genetic rat models of human diseases.

Keywords: Rats, transgenic, tetracycline-controlled transactivator, tTA, Doxycycline, Leucine Rich Repeat Kinase 2, LRRK2