title: Depot formation of doxycycline impairs Tet-regulated gene expression in vivo.
abstract: The tetracycline (Tet) system is widely used for regulation of gene expression in vitro and in vivo. We constructed C57BL/6 transgenic mice (rtTA-CM2) with strong and ubiquitous reverse transactivator (rtTA2(S)-M2) gene expression. rtTA-CM2 mice were crossed to Tet-responsive reporter mice (LC-1) conditionally expressing the firefly luciferase (FLuc) gene under control of a Tet-responsive element, which allowed sensitive quantification of the transactivator activity by bioluminescent imaging. Following doxycycline (dox) application, up to 10(5)-fold increase in BL signal was measured. rtTA activity was inducible in most analyzed organs. After dox withdrawal the BL signal decreased significantly but did not disappear completely, most likely due to a dox depot formation in vivo. The residual dox was sufficient to partly down-regulate a Tet-off controlled oncogene in a tumor transplantation experiment, resulting in reduced tumor growth. rtTA-CM2 mice may be a useful tool to analyze the function of genes in various organs but also reveal that down-regulation of gene expression is not complete.
authors.affiliation: Max-Delbrück-Center for Molecular Medicine, Robert-Rössle-Strasse 10, 13125, Berlin, Germany.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Anders
authors.forename: Christian
authors.initials: C
authors.lastname: Buschow
authors.forename: Jehad
authors.initials: J
authors.lastname: Charo
authors.forename: Thomas
authors.initials: T
authors.lastname: Blankenstein
mesh_terms: D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology; D003433:Crosses, Genetic; D004318:Doxycycline / Q000494:pharmacology*; D004354:Drug Screening Assays, Antitumor / Q000379:methods; D018703:Founder Effect; D015972:Gene Expression Regulation, Neoplastic; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008163:Luminescent Measurements; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008845:Microinjections; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D011401:Promoter Regions, Genetic; D013539:Simian virus 40 / Q000235:genetics; D053719:Tandem Mass Spectrometry; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D019076:Transgenes
chemical_list: D000952:Antigens, Polyomavirus Transforming; D000970:Antineoplastic Agents; D015514:Oncogene Proteins, Fusion; D015534:Trans-Activators; D008156:Luciferases; D004318:Doxycycline