title: Developing tTA transgenic rats for inducible and reversible gene expression.
abstract: 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 microg/ml in drinking water) for two days to reach the effective concentration, and then was given at a low dose (20 microg/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.
authors.affiliation: Department of Pathology, Anatomy & Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: Hongxia
authors.initials: H
authors.lastname: Zhou
authors.forename: Cao
authors.initials: C
authors.lastname: Huang
authors.forename: Min
authors.initials: M
authors.lastname: Yang
authors.forename: Carlisle P
authors.initials: CP
authors.lastname: Landel
authors.forename: Pedro Yuxing
authors.initials: PY
authors.lastname: Xia
authors.forename: Yong-Jian
authors.initials: YJ
authors.lastname: Liu
authors.forename: Xu Gang
authors.initials: XG
authors.lastname: Xia
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000833:Animals, Suckling; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D019921:Biotinylation; D004305:Dose-Response Relationship, Drug; D004318:Doxycycline / Q000494:pharmacology; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D005786:Gene Expression Regulation / Q000187:drug effects*; D017930:Genes, Reporter; D007150:Immunohistochemistry; D011247:Pregnancy; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D055647:Rats, Transgenic; D013752:Tetracycline / Q000494:pharmacology*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D019076:Transgenes / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D012333:RNA, Messenger; D015534:Trans-Activators; D013752:Tetracycline; D004318:Doxycycline