title: FLP and Cre recombinase function in Xenopus embryos.
abstract: The use of the site-specific DNA recombinases FLP and Cre is well-established in a broad range of organisms. Here we investigate the applicability of both recombinases to the Xenopus system where they have not been analyzed yet. We show that injection of FLP mRNA triggers the excision of an FLP recombination target (FRT)-flanked green fluorescent protein (GFP) sequence in a coinjected reporter construct inducing the expression of a downstream beta-galactosidase gene (lacZ). The FLP-mediated gene activation can be controlled in Xenopus embryos by injecting a mRNA encoding a fusion of FLP to the mutant ligand binding domain of the human estrogen receptor whose activity is dependent on 4-hydroxytamoxifen. We also demonstrate that a Cre reporter injected into fertilized eggs is fully recombined by Cre recombinase before zygotic gene transcription initiates. Our results indicate that in Xenopus embryos Cre is more effective than FLP in recombining a given quantity of reporter molecules. Finally, we present FLP-inducible double reporter systems encoding two fluorescence proteins (EYFP, ECFP, DsRed or GFP). These novel gene expression systems enable the continuous analysis of two reporter activities within living embryos and are expected to allow cell-lineage studies based on recombinase-mediated DNA rearrangement in transgenic Xenopus lines.
authors.affiliation: Universitätsklinikum Essen, Institut für Zellbiologie (Tumorforschung), Hufelandstrasse 55, D-45122 Essen, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Werdien
authors.forename: G
authors.initials: G
authors.lastname: Peiler
authors.forename: G U
authors.initials: GU
authors.lastname: Ryffel
mesh_terms: D000818:Animals; D003587:Cytomegalovirus / Q000235:genetics; D004254:DNA Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000378:metabolism*; D005786:Gene Expression Regulation; D049452:Green Fluorescent Proteins; D006801:Humans; D019426:Integrases / Q000235:genetics / Q000378:metabolism*; D007763:Lac Operon / Q000235:genetics; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011995:Recombination, Genetic; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000494:pharmacology; D015533:Transcriptional Activation; D014764:Viral Proteins; D014982:Xenopus laevis
chemical_list: D008164:Luminescent Proteins; D014764:Viral Proteins; D013629:Tamoxifen; D049452:Green Fluorescent Proteins; C016601:afimoxifene; C045073:Cre recombinase; D004254:DNA Nucleotidyltransferases; C045119:FLP recombinase; D019426:Integrases