The tamoxifen-inducible Cre-lox P system is widely used to overcome gene targeting pre-adult lethality, to modify a specific cell population at desired time-points, and to visualize and trace cells in fate-mapping studies. In this study we focused on tamoxifen degradation kinetics, because for all genetic fate-mapping studies, the period during which tamoxifen or its metabolites remain active in the CNS, is essential. Additionally, we aimed to define the tamoxifen administration scheme, enabling the maximal recombination rate together with minimal animal mortality. The time window between tamoxifen injection and the beginning of experiments should be large enough to allow complete degradation of tamoxifen and its metabolites. Otherwise, these substances could promote an undesired recombination, leading to data misinterpretation. We defined the optimal time window, allowing the complete degradation of tamoxifen and its metabolites, such as 4-hydroxytamoxifen, N-desmethyltamoxifen, endoxifen and norendoxifen, in the mouse brain after intraperitoneal tamoxifen injection. We determined the biological activity of these substances in vitro, as well as a minimal effective concentration of the most potent metabolite 4-hydroxytamoxifen causing recombination in vivo. Tissue-specific and time-dependent control of in vivo gene disruption may be achieved using conditional knockout strategies in transgenic mice. Fusion of mutant estrogen receptor ligand-binding domains to Cre recombinase (Cre-ER, Mer Cre Mer) combined with cardiac-directed gene expression has been used to generate several cardiac-specific tamoxifen-inducible Cre-expressing mouse lines. Such mice have successfully been used to generate Cre-lox P-mediated gene disruption in an inducible manner in the myocardium in vivo. However, information is sparse regarding the tamoxifen dosage, the time course of gene disruption and whether different administration routes differ in efficiency in obtaining gene disruption in the myocardium. We have evaluated these parameters in We thank Carsten Lund for advice on feed, Dag Markus Eide, National Institute of Public Health, for lending us mouse feeders, Roy Trondsen for designing mouse feeders, Marianne Lunde Sneve for technical assistance, Heidi Kvaløy and Ulla H. Enger for help with testing tamoxifen feed pellets. KBA was funded by Southeastern Norway Regional Health Authority and University of Oslo EMBIO senior fellow grants. Propranolol hypertension Buy synthroid in canada Here we describe how tamoxifen-dependent Cre recombinases, so-called CreER. the generation of experimental mice for inducible gene knockout studies, the. Nov 1, 2000. Expression of this inducible Cre recombinase was placed under the. Indeed, one major limitation of using tamoxifen in vivo may be its toxicity. Feb 11, 2010. To introduce a temporal control in the genetic experiments targeting the podocyte, we constructed tamoxifen-inducible Cre recombinase. The Cre-lox system, derived from P1 bacteriophage, is a potent and specific system for controlling gene expression. The protein Cre recombinase recognizes 34 bp lox P sites, and the orientation and location of the lox P sites determines how the genetic material will be rearranged. The schematic below shows the three types of rearrangements: inversion, deletion and translocation. For a more thorough introduction, check out Addgene’s Cre-lox blog post. Based on these Cre-lox recombination principles, scientists have developed constructs to activate/inactivate genes when Cre is present. By expressing Cre at specific times or locations, you can precisely control expression of your gene of interest. Many Cre constructs also contain fluorescent labels that indicate if recombination has occurred, allowing for direct comparison of Cre and Cre- cells. 1Department of Medicine and Clinical Science, Kyoto University Graduate School of Medicine, Kyoto, Kyoto, Japan2Department of Nephrology and Blood Purification, Institute of Biomedical Research and Innovation, Kobe, Hyogo, Japan Background. Podocytes play an important role in maintaining normal glomerular function. A podocyte-specific conditional knockout technology has been established by the use of transgenic mice expressing a podocyte-specific Cre recombinase to clarify the role of genes expressed in the podocytes. However, it may be difficult to examine the role of genes in certain pathologic conditions using conventional podocyte-specific knockout mice because they may be embryonically lethal or exhibit congenital renal abnormality. To introduce a temporal control in the genetic experiments targeting the podocyte, we constructed tamoxifen-inducible Cre recombinase (Cre ER) transgenic mice under the control of podocyte-specific promoter, 2.5-kb fragment of the human podocin (NPHS2) gene. The specificity and efficiency of Cre activity were examined by crossing NPHS2–Cre ER/R26R treated with 4-OHT expressed β-galactosidase specifically in 85% of the podocytes in glomeruli. Expression of Cre recombinase m RNA was mostly restricted to the kidney, especially in glomeruli. In conclusion, we have successfully generated podocyte-specific inducible Cre transgenic mice by tamoxifen administration. These mice allow us to disrupt the genes specifically in the podocytes after birth. Tamoxifen inducible cre Inducible Cre Mice, Inducible Gene Expression and Gene Modification in Transgenic Mice. Buy erythromycin benzoyl peroxide topical gel online Inducible Cre These constructs require the addition of an exogenous ligand e.g. tamoxifen to activate Cre. One advantage of this system is tight temporal. Addgene Cre-lox system. Podocyte-specific expression of tamoxifen-inducible Cre recombinase.. Intraperitoneal Injection of Tamoxifen for Inducible Cre-Driver Lines. We have produced Cre transgenic mice in which excision is tamoxifen inducible and occurs in a widespread mosaic pattern. We utilized our Cre excision. For tamoxifen-dependent Cre recombinase, also known as CreER recombinase, tamoxifen TAM is used to activate the Cre to generate time- and. The tamoxifen-inducible Cre-loxP system is widely used to overcome gene targeting pre-adult lethality, to modify a specific cell population at desired time-points.