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Novel system for efficient isolation of Clostridium double-crossover allelic exchange mutants enabling markerless chromosomal gene deletions and DNA integration. Appl Environ Microbiol 2012; 78:8112-21. [PMID: 22983967 DOI: 10.1128/aem.02214-12] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Isolation of Clostridium mutants based on gene replacement via allelic exchange remains a major limitation for this important genus. Use of a heterologous counterselection marker can facilitate the identification of the generally rare allelic exchange events. We report on the development of an inducible counterselection marker and describe its utility and broad potential in quickly and efficiently generating markerless DNA deletions and integrations at any genomic locus without the need for auxotrophic mutants or the use of the mobile group II introns. This system is based on a codon-optimized mazF toxin gene from Escherichia coli under the control of a lactose-inducible promoter from Clostridium perfringens. This system is potentially applicable to almost all members of the genus Clostridium due to their similarly low genomic GC content and comparable codon usage. We isolated all allelic-exchange-based gene deletions (ca_p0167, sigF, and sigK) or disruptions (ca_p0157 and sigF) we attempted and integrated a 3.6-kb heterologous DNA sequence (made up of a Clostridium ljungdahlii 2.1-kb formate dehydrogenase [fdh] gene plus a FLP recombination target [FRT]-flanked thiamphenicol resistance marker) into the Clostridium acetobutylicum chromosome. Furthermore, we report on the development of a plasmid system with inducible segregational instability, thus enabling efficient deployment of the FLP-FRT system to generate markerless deletion or integration mutants. This enabled expeditious deletion of the thiamphenicol resistance marker from the fdh integrant strain as well as the sigK deletion strain. More generally, our system can potentially be applied to other organisms with underdeveloped genetic tools.
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Long DP, Zhao AC, Chen XJ, Zhang Y, Lu WJ, Guo Q, Handler AM, Xiang ZH. FLP recombinase-mediated site-specific recombination in silkworm, Bombyx mori. PLoS One 2012; 7:e40150. [PMID: 22768245 PMCID: PMC3387143 DOI: 10.1371/journal.pone.0040150] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 06/01/2012] [Indexed: 11/18/2022] Open
Abstract
A comprehensive understanding of gene function and the production of site-specific genetically modified mutants are two major goals of genetic engineering in the post-genomic era. Although site-specific recombination systems have been powerful tools for genome manipulation of many organisms, they have not yet been established for use in the manipulation of the silkworm Bombyx mori genome. In this study, we achieved site-specific excision of a target gene at predefined chromosomal sites in the silkworm using a FLP/FRT site-specific recombination system. We first constructed two stable transgenic target silkworm strains that both contain a single copy of the transgene construct comprising a target gene expression cassette flanked by FRT sites. Using pre-blastoderm microinjection of a FLP recombinase helper expression vector, 32 G3 site-specific recombinant transgenic individuals were isolated from five of 143 broods. The average frequency of FLP recombinase-mediated site-specific excision in the two target strains genome was approximately 3.5%. This study shows that it is feasible to achieve site-specific recombination in silkworms using the FLP/FRT system. We conclude that the FLP/FRT system is a useful tool for genome manipulation in the silkworm. Furthermore, this is the first reported use of the FLP/FRT system for the genetic manipulation of a lepidopteran genome and thus provides a useful reference for the establishment of genome manipulation technologies in other lepidopteran species.
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Affiliation(s)
- Ding-Pei Long
- State Key Laboratory of Silkworm Genome Biology, Institute of Sericulture and Systems Biology, Southwest University, Chongqing, China
| | - Ai-Chun Zhao
- State Key Laboratory of Silkworm Genome Biology, Institute of Sericulture and Systems Biology, Southwest University, Chongqing, China
- * E-mail:
| | - Xue-Jiao Chen
- State Key Laboratory of Silkworm Genome Biology, Institute of Sericulture and Systems Biology, Southwest University, Chongqing, China
| | - Yang Zhang
- State Key Laboratory of Silkworm Genome Biology, Institute of Sericulture and Systems Biology, Southwest University, Chongqing, China
| | - Wei-Jian Lu
- State Key Laboratory of Silkworm Genome Biology, Institute of Sericulture and Systems Biology, Southwest University, Chongqing, China
| | - Qing Guo
- State Key Laboratory of Silkworm Genome Biology, Institute of Sericulture and Systems Biology, Southwest University, Chongqing, China
| | - Alfred M. Handler
- USDA/ARS, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, United States of America
| | - Zhong-Huai Xiang
- State Key Laboratory of Silkworm Genome Biology, Institute of Sericulture and Systems Biology, Southwest University, Chongqing, China
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Joint control of Drosophila male courtship behavior by motion cues and activation of male-specific P1 neurons. Proc Natl Acad Sci U S A 2012; 109:10065-70. [PMID: 22645338 DOI: 10.1073/pnas.1207107109] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Sexual behaviors in animals are governed by inputs from multiple external sensory modalities. However, how these inputs are integrated to jointly control animal behavior is still poorly understood. Whereas visual information alone is not sufficient to induce courtship behavior in Drosophila melanogaster males, when a subset of male-specific fruitless (fru)- and doublesex (dsx)-expressing neurons that respond to chemosensory cues (P1 neurons) were artificially activated via a temperature-sensitive cation channel (dTRPA1), males followed and extended their wing toward moving objects (even a moving piece of rubber band) intensively. When stationary, these objects were not courted. Our results indicate that motion input and activation of P1 neurons are individually necessary, and under our assay conditions, jointly sufficient to elicit early courtship behaviors, and provide insights into how courtship decisions are made via sensory integration.
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Giovannini D, Späth S, Lacroix C, Perazzi A, Bargieri D, Lagal V, Lebugle C, Combe A, Thiberge S, Baldacci P, Tardieux I, Ménard R. Independent roles of apical membrane antigen 1 and rhoptry neck proteins during host cell invasion by apicomplexa. Cell Host Microbe 2012; 10:591-602. [PMID: 22177563 DOI: 10.1016/j.chom.2011.10.012] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2011] [Revised: 09/01/2011] [Accepted: 10/07/2011] [Indexed: 10/14/2022]
Abstract
During invasion, apicomplexan parasites form an intimate circumferential contact with the host cell, the tight junction (TJ), through which they actively glide. The TJ, which links the parasite motor to the host cell cytoskeleton, is thought to be composed of interacting apical membrane antigen 1 (AMA1) and rhoptry neck (RON) proteins. Here we find that, in Plasmodium berghei, while both AMA1 and RON4 are important for merozoite invasion of erythrocytes, only RON4 is required for sporozoite invasion of hepatocytes, indicating that RON4 acts independently of AMA1 in the sporozoite. Further, in the Toxoplasma gondii tachyzoite, AMA1 is dispensable for normal RON4 ring and functional TJ assembly but enhances tachyzoite apposition to the cell and internalization frequency. We propose that while the RON proteins act at the TJ, AMA1 mainly functions on the zoite surface to permit correct attachment to the cell, which may facilitate invasion depending on the zoite-cell combination.
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Affiliation(s)
- Donatella Giovannini
- Institut Pasteur, Unité de Biologie et Génétique du Paludisme, 75724 Paris, France
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Li J, Goossens S, van Hengel J, Gao E, Cheng L, Tyberghein K, Shang X, De Rycke R, van Roy F, Radice GL. Loss of αT-catenin alters the hybrid adhering junctions in the heart and leads to dilated cardiomyopathy and ventricular arrhythmia following acute ischemia. J Cell Sci 2012; 125:1058-67. [PMID: 22421363 DOI: 10.1242/jcs.098640] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
It is generally accepted that the intercalated disc (ICD) required for mechano-electrical coupling in the heart consists of three distinct junctional complexes: adherens junctions, desmosomes and gap junctions. However, recent morphological and molecular data indicate a mixing of adherens junctional and desmosomal components, resulting in a 'hybrid adhering junction' or 'area composita'. The α-catenin family member αT-catenin, part of the N-cadherin-catenin adhesion complex in the heart, is the only α-catenin that interacts with the desmosomal protein plakophilin-2 (PKP2). Thus, it has been postulated that αT-catenin might serve as a molecular integrator of the two adhesion complexes in the area composita. To investigate the role of αT-catenin in the heart, gene targeting technology was used to delete the Ctnna3 gene, encoding αT-catenin, in the mouse. The αT-catenin-null mice are viable and fertile; however, the animals exhibit progressive cardiomyopathy. Adherens junctional and desmosomal proteins were unaffected by loss of αT-catenin, with the exception of the desmosomal protein PKP2. Immunogold labeling at the ICD demonstrated in the αT-catenin-null heart a preferential reduction of PKP2 at the area composita compared with the desmosome. Furthermore, gap junction protein Cx43 was reduced at the ICD, including its colocalization with N-cadherin. Gap junction remodeling in αT-catenin-knockout hearts was associated with an increased incidence of ventricular arrhythmias after acute ischemia. This novel animal model demonstrates for the first time how perturbation in αT-catenin can affect both PKP2 and Cx43 and thereby highlights the importance of understanding the crosstalk between the junctional proteins of the ICD and its implications for arrhythmogenic cardiomyopathy.
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Affiliation(s)
- Jifen Li
- Center for Translational Medicine, Department of Medicine, Thomas Jefferson University, Philadelphia, PA, USA
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56
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[Progress in Cre/lox site-specific recombination system in higher eukaryotes]. YI CHUAN = HEREDITAS 2012; 34:177-89. [PMID: 22382059 DOI: 10.3724/sp.j.1005.2012.00177] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Cre/lox system derived from P1 bacteriaphage can quickly and effectively achieve gene insertion, deletion, replacement, and inversion by means of site-specific recombination. As one of the most important tools for gene targeting at present, Cre/lox system has been widely used in Arabidopsis thaliana, Oryza sativa L., Mus musculus, Drosophila melanogaster, Danio rerio, and other higher eukaryotic organisms. This review roundly described the basic profile of Cre/lox system, and its application in higher eukaryotes. In addition, we also discussed the main problems and developmental trend of the Cre/lox system in this review, which can be a good reference for using Cre/lox system to realize the gene manipulations of the different high eukaryotic organisms.
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Wong SP, Argyros O, Harbottle RP. Vector systems for prenatal gene therapy: principles of non-viral vector design and production. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2012; 891:133-67. [PMID: 22648771 DOI: 10.1007/978-1-61779-873-3_7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Gene therapy vectors based on viruses are the most effective gene delivery systems in use today and although efficient at gene transfer their potential toxicity (Hacein-Bey-Abina et al., Science 302:415-419, 2003) provides impetus for the development of safer non-viral alternatives. An ideal vector for human gene therapy should deliver sustainable therapeutic levels of gene expression without affecting the viability of the host at either the cellular or somatic level. Vectors, which comprise entirely human elements, may provide the most suitable method of achieving this. Non-viral vectors are attractive alternatives to viral gene delivery systems because of their low toxicity, relatively easy production, and great versatility. The development of more efficient, economically prepared, and safer gene delivery vectors is a crucial prerequisite for their successful clinical application and remains a primary strategic task of gene therapy research.
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Affiliation(s)
- Suet Ping Wong
- Faculty of Medicine, Molecular and Cellular Medicine Section, National Heart and Lung Institute, Imperial College London, London, UK
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58
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Abstract
The ability to manipulate the genomes of many insects has become a practical reality over the past 15 years. This has been led by the identification of several useful transposon vector systems that have allowed the identification and development of generalized, species-specific, and tissue-specific promoter systems for controlled expression of gene products upon introduction into insect genomes. Armed with these capabilities, researchers have made significant strides in both fundamental and applied transgenics in key model systems such as Bombyx mori, Tribolium casteneum, Aedes aegypti, and Anopheles stephensi. Limitations of transposon systems were identified, and alternative tools were developed, thus significantly increasing the potential for applied transgenics for control of both agricultural and medical insect pests. The next 10 years promise to be an exciting time of transitioning from the laboratory to the field, from basic research to applied control, during which the full potential of gene manipulation in insect systems will ultimately be realized.
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Affiliation(s)
- Malcolm J Fraser
- Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556-0369, USA.
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59
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Garwick-Coppens SE, Herman A, Harper SQ. Construction of permanently inducible miRNA-based expression vectors using site-specific recombinases. BMC Biotechnol 2011; 11:107. [PMID: 22087765 PMCID: PMC3252340 DOI: 10.1186/1472-6750-11-107] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Accepted: 11/16/2011] [Indexed: 12/30/2022] Open
Abstract
Background RNA interference (RNAi) is a conserved gene silencing mechanism mediated by small inhibitory microRNAs (miRNAs). Promoter-driven miRNA expression vectors have emerged as important tools for delivering natural or artificially designed miRNAs to eukaryotic cells and organisms. Such systems can be used to query the normal or pathogenic functions of natural miRNAs or messenger RNAs, or to therapeutically silence disease genes. Results As with any molecular cloning procedure, building miRNA-based expression constructs requires a time investment and some molecular biology skills. To improve efficiency and accelerate the construction process, we developed a method to rapidly generate miRNA expression vectors using recombinases instead of more traditional cut-and-paste molecular cloning techniques. In addition to streamlining the construction process, our cloning strategy provides vectors with added versatility. In our system, miRNAs can be constitutively expressed from the U6 promoter, or inducibly expressed by Cre recombinase. We also engineered a built-in mechanism to destroy the vector with Flp recombinase, if desired. Finally, to further simplify the construction process, we developed a software package that automates the prediction and design of optimal miRNA sequences using our system. Conclusions We designed and tested a modular system to rapidly clone miRNA expression cassettes. Our strategy reduces the hands-on time required to successfully generate effective constructs, and can be implemented in labs with minimal molecular cloning expertise. This versatile system provides options that permit constitutive or inducible miRNA expression, depending upon the needs of the end user. As such, it has utility for basic or translational applications.
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Affiliation(s)
- Sara E Garwick-Coppens
- Center for Gene Therapy, The Research Institute at Nationwide Children's Hospital, Columbus, Ohio, 43205, USA
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60
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Lacroix C, Giovannini D, Combe A, Bargieri DY, Späth S, Panchal D, Tawk L, Thiberge S, Carvalho TG, Barale JC, Bhanot P, Ménard R. FLP/FRT-mediated conditional mutagenesis in pre-erythrocytic stages of Plasmodium berghei. Nat Protoc 2011; 6:1412-28. [DOI: 10.1038/nprot.2011.363] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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61
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Hérault Y, Duchon A, Maréchal D, Raveau M, Pereira PL, Dalloneau E, Brault V. Controlled somatic and germline copy number variation in the mouse model. Curr Genomics 2011; 11:470-80. [PMID: 21358991 PMCID: PMC3018727 DOI: 10.2174/138920210793176038] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2010] [Revised: 05/24/2010] [Accepted: 05/27/2010] [Indexed: 12/20/2022] Open
Abstract
Changes in the number of chromosomes, but also variations in the copy number of chromosomal regions have been described in various pathological conditions, such as cancer and aneuploidy, but also in normal physiological condition. Our classical view of DNA replication and mitotic preservation of the chromosomal integrity is now challenged as new technologies allow us to observe such mosaic somatic changes in copy number affecting regions of chromosomes with various sizes. In order to go further in the understanding of copy number influence in normal condition we could take advantage of the novel strategy called Targeted Asymmetric Sister Chromatin Event of Recombination (TASCER) to induce recombination during the G2 phase so that we can generate deletions and duplications of regions of interest prior to mitosis. Using this approach in the mouse we could address the effects of copy number variation and segmental aneuploidy in daughter cells and allow us to explore somatic mosaics for large region of interest in the mouse.
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Affiliation(s)
- Yann Hérault
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR7104, Université de Strasbourg, Illkirch, France
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62
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Takata Y, Kondo S, Goda N, Kanegae Y, Saito I. Comparison of efficiency between FLPe and Cre for recombinase-mediated cassette exchange in vitro and in adenovirus vector production. Genes Cells 2011; 16:765-77. [DOI: 10.1111/j.1365-2443.2011.01526.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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63
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Turan S, Galla M, Ernst E, Qiao J, Voelkel C, Schiedlmeier B, Zehe C, Bode J. Recombinase-Mediated Cassette Exchange (RMCE): Traditional Concepts and Current Challenges. J Mol Biol 2011; 407:193-221. [DOI: 10.1016/j.jmb.2011.01.004] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2010] [Revised: 01/04/2011] [Accepted: 01/04/2011] [Indexed: 12/18/2022]
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64
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Wang Y, Yau YY, Perkins-Balding D, Thomson JG. Recombinase technology: applications and possibilities. PLANT CELL REPORTS 2011; 30:267-85. [PMID: 20972794 PMCID: PMC3036822 DOI: 10.1007/s00299-010-0938-1] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Revised: 10/06/2010] [Accepted: 10/08/2010] [Indexed: 05/02/2023]
Abstract
The use of recombinases for genomic engineering is no longer a new technology. In fact, this technology has entered its third decade since the initial discovery that recombinases function in heterologous systems (Sauer in Mol Cell Biol 7(6):2087-2096, 1987). The random insertion of a transgene into a plant genome by traditional methods generates unpredictable expression patterns. This feature of transgenesis makes screening for functional lines with predictable expression labor intensive and time consuming. Furthermore, an antibiotic resistance gene is often left in the final product and the potential escape of such resistance markers into the environment and their potential consumption raises consumer concern. The use of site-specific recombination technology in plant genome manipulation has been demonstrated to effectively resolve complex transgene insertions to single copy, remove unwanted DNA, and precisely insert DNA into known genomic target sites. Recombinases have also been demonstrated capable of site-specific recombination within non-nuclear targets, such as the plastid genome of tobacco. Here, we review multiple uses of site-specific recombination and their application toward plant genomic engineering. We also provide alternative strategies for the combined use of multiple site-specific recombinase systems for genome engineering to precisely insert transgenes into a pre-determined locus, and removal of unwanted selectable marker genes.
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Affiliation(s)
- Yueju Wang
- Department of Natural Sciences, Northeastern State University, Broken Arrow, OK 74014 USA
| | - Yuan-Yeu Yau
- Department of Plant and Microbial Biology, Plant Gene Expression Center, USDA-ARS, University of California-Berkeley, 800 Buchanan St., Albany, CA 94710 USA
| | | | - James G. Thomson
- Crop Improvement and Utilization Unit, USDA-ARS WRRC, 800 Buchanan St., Albany, CA 94710 USA
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65
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Kranz A, Fu J, Duerschke K, Weidlich S, Naumann R, Stewart AF, Anastassiadis K. An improved Flp deleter mouse in C57Bl/6 based on Flpo recombinase. Genesis 2011; 48:512-20. [PMID: 20506501 DOI: 10.1002/dvg.20641] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Recently, a codon improved version of the Flpe site specific recombinase, termed Flpo, was reported as having greatly improved performance in mammalian cell applications. However, the degree of improvement could not be estimated because essentially no Flpe activity was observed. Here, we compare Flpe and Flpo accurately in a mammalian cell assay to estimate that Flpo is about five times more active than Flpe and similar to Cre and Dre. Consequently, we generated a Flpo deleter mouse line from the JM8 C57Bl/6 ES cells used in the EUCOMM and KOMP systematic knock-out programs. In breeding experiments, we show that the Flpo deleter delivers complete recombination using alleles that are incompletely recombined by a commonly used Flpe deleter. This indicates that the Flpo deleter is more efficient.
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Affiliation(s)
- Andrea Kranz
- Genomics, BioInnovationsZentrum, Technische Universität Dresden, Am Tatzberg 47, Dresden, Germany
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66
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van Schaijk BCL, Vos MW, Janse CJ, Sauerwein RW, Khan SM. Removal of heterologous sequences from Plasmodium falciparum mutants using FLPe-recombinase. PLoS One 2010; 5:e15121. [PMID: 21152048 PMCID: PMC2994908 DOI: 10.1371/journal.pone.0015121] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2010] [Accepted: 10/22/2010] [Indexed: 01/23/2023] Open
Abstract
Genetically-modified mutants are now indispensable Plasmodium gene-function reagents, which are also being pursued as genetically attenuated parasite vaccines. Currently, the generation of transgenic malaria-parasites requires the use of drug-resistance markers. Here we present the development of an FRT/FLP-recombinase system that enables the generation of transgenic parasites free of resistance genes. We demonstrate in the human malaria parasite, P. falciparum, the complete and efficient removal of the introduced resistance gene. We targeted two neighbouring genes, p52 and p36, using a construct that has a selectable marker cassette flanked by FRT-sequences. This permitted the subsequent removal of the selectable marker cassette by transient transfection of a plasmid that expressed a 37°C thermostable and enhanced FLP-recombinase. This method of removing heterologous DNA sequences from the genome opens up new possibilities in Plasmodium research to sequentially target multiple genes and for using genetically-modified parasites as live, attenuated malaria vaccines.
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Affiliation(s)
- Ben C. L. van Schaijk
- Department of Medical Microbiology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands
- * E-mail: ) (BCLvS); (SMK)
| | - Martijn W. Vos
- Department of Medical Microbiology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands
| | - Chris J. Janse
- Leiden Malaria Research Group, Department of Parasitology, Center of Infectious Diseases, Leiden University Medical Centre, Leiden, The Netherlands
| | - Robert W. Sauerwein
- Department of Medical Microbiology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands
| | - Shahid M. Khan
- Leiden Malaria Research Group, Department of Parasitology, Center of Infectious Diseases, Leiden University Medical Centre, Leiden, The Netherlands
- * E-mail: ) (BCLvS); (SMK)
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67
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Khrunyk Y, Münch K, Schipper K, Lupas AN, Kahmann R. The use of FLP-mediated recombination for the functional analysis of an effector gene family in the biotrophic smut fungus Ustilago maydis. THE NEW PHYTOLOGIST 2010; 187:957-968. [PMID: 20673282 DOI: 10.1111/j.1469-8137.2010.03413.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
*In the Ustilago maydis genome, several novel secreted effector proteins are encoded by gene families. Because of the limited number of selectable markers, the ability to carry out sequential gene deletions has limited the analysis of effector gene families that may have redundant functions. *Here, we established an inducible FLP-mediated recombination system in U. maydis that allows repeated rounds of gene deletion using a single selectable marker (Hyg(R)). To avoid genome rearrangements via FRT sites remaining in the genome after excision, different mutated FRT sites were introduced. *The FLP-mediated selectable marker-removal technique was successfully applied to delete a family of 11 effector genes (eff1) using five sequential rounds of recombination. We showed that expression of all 11 genes is up-regulated during the biotrophic phase. Strains carrying deletions of 9 or all 11 genes showed a significant reduction in virulence, and this phenotype could be partially complemented by the introduction of different members from the gene family, demonstrating redundancy. *The establishment of the FLP/FRT system in a plant pathogenic fungus paves the way for analyzing multigene families with redundant functions.
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Affiliation(s)
- Yuliya Khrunyk
- Department of Organismic Interactions, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Strasse 10, D-35043 Marburg, Germany
| | - Karin Münch
- Department of Organismic Interactions, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Strasse 10, D-35043 Marburg, Germany
| | - Kerstin Schipper
- Department of Organismic Interactions, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Strasse 10, D-35043 Marburg, Germany
| | - Andrei N Lupas
- Department of Protein Evolution, Max Planck Institute for Developmental Biology, Spemannstr. 35, D-72076 Tübingen, Germany
| | - Regine Kahmann
- Department of Organismic Interactions, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Strasse 10, D-35043 Marburg, Germany
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68
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Canalis E, Zanotti S, Beamer WG, Economides AN, Smerdel-Ramoya A. Connective tissue growth factor is required for skeletal development and postnatal skeletal homeostasis in male mice. Endocrinology 2010; 151:3490-501. [PMID: 20534727 PMCID: PMC2940511 DOI: 10.1210/en.2010-0145] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Accepted: 05/04/2010] [Indexed: 01/11/2023]
Abstract
Connective tissue growth factor (CTGF), a member of the cysteine-rich 61 (Cyr 61), CTGF, nephroblastoma overexpressed (NOV) (CCN) family of proteins, is synthesized by osteoblasts, and its overexpression inhibits osteoblastogenesis and causes osteopenia. The global inactivation of Ctgf leads to defective endochondral bone formation and perinatal lethality; therefore, the consequences of Ctgf inactivation on the postnatal skeleton are not known. To study the function of CTGF, we generated Ctgf(+/LacZ) heterozygous null mice and tissue-specific null Ctgf mice by mating Ctgf conditional mice, where Ctgf is flanked by lox sequences with mice expressing the Cre recombinase under the control of the paired-related homeobox gene 1 (Prx1) enhancer (Prx1-Cre) or the osteocalcin promoter (Oc-Cre). Ctgf(+/LacZ) heterozygous mice exhibited transient osteopenia at 1 month of age secondary to decreased trabecular number. A similar osteopenic phenotype was observed in 1-month-old Ctgf conditional null male mice generated with Prx1-Cre, suggesting that the decreased trabecular number was secondary to impaired endochondral bone formation. In contrast, when the conditional deletion of Ctgf was achieved by Oc-Cre, an osteopenic phenotype was observed only in 6-month-old male mice. Osteoblast and osteoclast number, bone formation, and eroded surface were not affected in Ctgf heterozygous or conditional null mice. In conclusion, CTGF is necessary for normal skeletal development but to a lesser extent for postnatal skeletal homeostasis.
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Affiliation(s)
- Ernesto Canalis
- Department of Research, Saint Francis Hospital and Medical Center, Hartford, Connecticut 06105-1299, USA.
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69
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Abstract
To assay the efficiency of the FLP/FRT site-specific recombination system in Danio rerio, a construct consisting of a muscle-specific promoter driving EGFP flanked by FRT sites was developed. FLPe capped RNA was microinjected into transgenic single cell stage zebrafish embryos obtained by crossing hemizygous transgenic males with wild-type females. By 48 h post fertilization (hpf), the proportion of embryos displaying green fluorescence following FLPe RNA microinjection was significantly lower (7.7%; P < 0.001) than would be expected from a cross in the absence of the recombinase (50%). Embryos that retained fluorescence displayed marked mosaicism. Inheritance of the excised transgene in non-fluorescent, transgenic embryos was verified by PCR analysis and FLPe-mediated recombination was confirmed by DNA sequencing. Sperm derived from confirmed transgenic males in these experiments was used to fertilize wild-type eggs to determine whether germline excision of the transgene had occurred. Clutches sired by FLPe-microinjected males contained 0-4% fluorescent embryos. Transgenic males that were phenotypically wild-type produced no fluorescent progeny, demonstrating complete excision of the transgene from their germline. FLPe microinjected males that retained some fluorescent muscle expression produced a small proportion of fluorescent offspring, suggesting that in mosaic males not all germline cells had undergone FLPe-mediated transgene excision. Our results show that FLPe, which is derived from Saccharomyces cerevisiae, is an efficient recombinase in zebrafish maintained at 28.5°C.
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70
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Dymecki SM, Ray RS, Kim JC. Mapping cell fate and function using recombinase-based intersectional strategies. Methods Enzymol 2010; 477:183-213. [PMID: 20699143 DOI: 10.1016/s0076-6879(10)77011-7] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/06/2022]
Abstract
Cell types are typically defined by expression of a unique combination of genes, rather than a single gene. Intersectional methods therefore become crucial to selectively access these cells for higher resolution fate mapping and functional manipulations. Here, we discuss one such intersectional method. Two recombinase systems (Cre/loxP and Flp/FRT) work together to remove a double STOP cassette and thereby activate expression of a target transgene solely in cells defined by a particular pairwise combination of driver genes. Depending on the nature of the target transgene, this strategy can be used to deliver cell-lineage tracers, sensors, and/or effector molecules to highly selective cell types in vivo. In this chapter, we discuss concepts, reagents, and methods underlying this intersectional approach and encourage consideration of various intersectional and binary methods for accessing uniquely defined cell subsets in the mouse.
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Affiliation(s)
- Susan M Dymecki
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, USA
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71
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Abstract
Understanding how cells are assembled in three dimensions to generate an organ, or a whole organism, is a pivotal question in developmental biology. Similarly, it is critical to understand how adult stem cells integrate into an existing organ during regeneration or in response to injury. Key to discovering the answers to these questions is being able to study the various behaviors of distinct cell types during development or regeneration. Fate mapping techniques are fundamental to studying cell behaviors such as proliferation, movement, and lineage segregation, as the techniques allow precursor cells to be marked and their descendants followed and characterized over time. The generation of transgenic mice, combined with the use of site-specific recombinases (SSR) in the mouse genome, has provided a means to develop powerful genetic fate mapping approaches. A key advantage of genetic fate mapping is that it allows cells to be genetically marked, and therefore the mark is transmitted to all the descendants of the initially marked cells. By making modifications to the SSRs that render their enzymatic activity inducible, and the development of an assortment of reporter alleles for marking cells, increasingly sophisticated genetic fate mapping studies can be performed. In this chapter, we review the four main genetic fate mapping methods that utilize intrachromosomal recombination to mark cells (cumulative, inducible, clonal, and intersectional) and one interchromosomal method, the tools required to carry out each approach, and the practical considerations that have to be taken into account before embarking on each type of genetic fate mapping study.
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Affiliation(s)
- Emilie Legué
- Memorial Sloan-Kettering Cancer Center, New York, USA
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Wakabayashi-Nakao K, Tamura A, Koshiba S, Toyoda Y, Nakagawa H, Ishikawa T. Production of cells with targeted integration of gene variants of human ABC transporter for stable and regulated expression using the Flp recombinase system. Methods Mol Biol 2010; 648:139-159. [PMID: 20700710 DOI: 10.1007/978-1-60761-756-3_9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The vector-mediated introduction of cDNA into mammalian cells by calcium phosphate co-precipitation or permeation with lipofectamine is widely used for the integration of cDNA into genomic DNA. Such integration, however, of cDNA occurs randomly at unpredictable sites in the host's chromosomal DNA, and the number of integrated recombinant DNAs is not controllable. To overcome this problem, we developed the Flp-In method to integrate one single copy of cDNA encoding the human ABC transporter ABCG2 into FRT-tagged genomic DNA. Examination of more than 20 metaphase spreads for both fluorescence in situ hybridization (FISH) mapping and multicolor-FISH analysis revealed that ABCG2 cDNA was incorporated into the telomeric region of the short arm on one of chromosomes 12 in Flp-In-293 cells. By using those cells, we investigated the effect of genetic polymorphisms and post-translational modifications of human ABC transporter ABCG2 on the protein expression and degradation. On the basis of our experience, it has been concluded that the Flp recombinase system provides a useful tool to quantitatively analyze the protein stability and endoplasmic reticulum (ER)-associated degradation of proteins like the ABC transporter. This system is also applicable for similar studies of the biogenesis of other proteins using the secretory pathway as well as proteins with other cellular localizations.
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73
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A Practical Summary of Site-Specific Recombination, Conditional Mutagenesis, and Tamoxifen Induction of CreERT2. Methods Enzymol 2010; 477:109-23. [DOI: 10.1016/s0076-6879(10)77007-5] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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74
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Capasso P, Aliprandi M, Ossolengo G, Edenhofer F, de Marco A. Monodispersity of recombinant Cre recombinase correlates with its effectiveness in vivo. BMC Biotechnol 2009; 9:80. [PMID: 19747375 PMCID: PMC2755479 DOI: 10.1186/1472-6750-9-80] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Accepted: 09/11/2009] [Indexed: 11/21/2022] Open
Abstract
Background Cre recombinase is a common reagent used for the in vivo on/off switching of the expression of target genes flanked by loxP sites. In particular, recombinant TAT-Cre fusion constructs purified from bacteria have been used to promote the cell uptake of the enzyme. However, the recovery of active TAT-Cre remains a demanding process and its specific activity varies significantly among batches, making difficult data comparison. Results We noticed a strong correlation between recombinase activity and enzyme monodispersity. The existence of such correlation enabled us to indirectly monitor the TAT-Cre recombinase activity during the multi-step purification process by measuring its monodispersity, a parameter detectable by means of a spectrofluorimetric assay that allows the calculation of the Aggregation Index (AI) in an easy and rapid way. AI values were recorded after each purification passage to identify the critical steps and to choose optimal alternatives for chromatographic conditions, desalting procedures, and protocols for bacterial endotoxin removal. Furthermore, the effect of metal ions and temperature on TAT-Cre aggregation and inactivation was characterized in vitro. Finally, we optimized the enzyme delivery protocol in vivo by following the accumulation tuning of the reporter protein β-catenin. Conclusion A rational purification protocol for TAT-Cre has been developed by choosing the options that minimize the enzyme aggregation. Our data suggest that AI measurement should support the optimization of any protocol aiming at the recovery of monodispersed protein.
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Affiliation(s)
- Paola Capasso
- Cogentech-Consortium for Genomics Technologies, via Adamello 16, 20139 Milan, Italy
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Anastassiadis K, Fu J, Patsch C, Hu S, Weidlich S, Duerschke K, Buchholz F, Edenhofer F, Stewart AF. Dre recombinase, like Cre, is a highly efficient site-specific recombinase in E. coli, mammalian cells and mice. Dis Model Mech 2009; 2:508-15. [PMID: 19692579 DOI: 10.1242/dmm.003087] [Citation(s) in RCA: 224] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Tyrosine site-specific recombinases (SSRs) including Cre and FLP are essential tools for DNA and genome engineering. Cre has long been recognized as the best SSR for genome engineering, particularly in mice. Obtaining another SSR that is as good as Cre will be a valuable addition to the genomic toolbox. To this end, we have developed and validated reagents for the Dre-rox system. These include an Escherichia coli-inducible expression vector based on the temperature-sensitive pSC101 plasmid, a mammalian expression vector based on the CAGGs promoter, a rox-lacZ reporter embryonic stem (ES) cell line based on targeting at the Rosa26 locus, the accompanying Rosa26-rox reporter mouse line, and a CAGGs-Dre deleter mouse line. We also show that a Dre-progesterone receptor shows good ligand-responsive induction properties. Furthermore, we show that there is no crossover recombination between Cre-rox or Dre-loxP. Hence, we add another set of efficient tools to the genomic toolbox, which will enable the development of more sophisticated mouse models for the analysis of gene function and disease.
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Affiliation(s)
- Konstantinos Anastassiadis
- Center for Regenerative Therapies Dresden, BioInnovationsZentrum Technische Universitaet Dresden, Am Tatzberg 47, 01307 Dresden, Germany
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76
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Activities of Various FLP Recombinases Expressed by Adenovirus Vectors in Mammalian Cells. J Mol Biol 2009; 390:221-30. [DOI: 10.1016/j.jmb.2009.04.057] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Revised: 04/24/2009] [Accepted: 04/27/2009] [Indexed: 11/18/2022]
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77
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Gulevich AY, Skorokhodova AY, Ermishev VY, Krylov AA, Minaeva NI, Polonskaya ZM, Zimenkov DV, Biryukova IV, Mashko SV. A new method for the construction of translationally coupled operons in a bacterial chromosome. Mol Biol 2009; 43:505-11. [DOI: 10.1134/s0026893309030194] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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78
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Itou J, Suyama M, Imamura Y, Deguchi T, Fujimori K, Yuba S, Kawarabayasi Y, Kawasaki T. Functional and comparative genomics analyses of pmp22 in medaka fish. BMC Neurosci 2009; 10:60. [PMID: 19534778 PMCID: PMC2714311 DOI: 10.1186/1471-2202-10-60] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2009] [Accepted: 06/17/2009] [Indexed: 01/23/2023] Open
Abstract
Background Pmp22, a member of the junction protein family Claudin/EMP/PMP22, plays an important role in myelin formation. Increase of pmp22 transcription causes peripheral neuropathy, Charcot-Marie-Tooth disease type1A (CMT1A). The pathophysiological phenotype of CMT1A is aberrant axonal myelination which induces a reduction in nerve conduction velocity (NCV). Several CMT1A model rodents have been established by overexpressing pmp22. Thus, it is thought that pmp22 expression must be tightly regulated for correct myelin formation in mammals. Interestingly, the myelin sheath is also present in other jawed vertebrates. The purpose of this study is to analyze the evolutionary conservation of the association between pmp22 transcription level and vertebrate myelin formation, and to find the conserved non-coding sequences for pmp22 regulation by comparative genomics analyses between jawed fishes and mammals. Results A transgenic pmp22 over-expression medaka fish line was established. The transgenic fish had approximately one fifth the peripheral NCV values of controls, and aberrant myelination of transgenic fish in the peripheral nerve system (PNS) was observed. We successfully confirmed that medaka fish pmp22 has the same exon-intron structure as mammals, and identified some known conserved regulatory motifs. Furthermore, we found novel conserved sequences in the first intron and 3'UTR. Conclusion Medaka fish undergo abnormalities in the PNS when pmp22 transcription increases. This result indicates that an adequate pmp22 transcription level is necessary for correct myelination of jawed vertebrates. Comparison of pmp22 orthologs between distantly related species identifies evolutionary conserved sequences that contribute to precise regulation of pmp22 expression.
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Affiliation(s)
- Junji Itou
- Department of Radiation Biomedical Science IV, Radiation Biology Center, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan.
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79
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Li W, Kotoshiba S, Kaldis P. Genetic mouse models to investigate cell cycle regulation. Transgenic Res 2009; 18:491-8. [PMID: 19418238 DOI: 10.1007/s11248-009-9276-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Accepted: 04/20/2009] [Indexed: 01/21/2023]
Abstract
Early studies on cell cycle regulation were based on experiments in model systems (Yeast, Xenopus, Starfish, Drosophila) and have shaped the way we understand many events that control the cell cycle. Although these model systems are of great value, the last decade was highlighted by studies done in human cells and using in vivo mouse models. Mouse models are irreplaceable tools for understanding the genetics, development, and survival strategies of mammals. New developments in generating targeting vectors and mutant mice have improved our approaches to study cell cycle regulation and cancer. Here we summarize the most recent advances of mouse model approaches in dissecting the mechanisms of cell cycle regulation and the relevance to human disease.
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Affiliation(s)
- Weimin Li
- Department of Pharmacology, University of Wisconsin-Madison, 3725 MSC, 1300 University Avenue, Madison, WI 53706, USA
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80
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Combe A, Giovannini D, Carvalho TG, Spath S, Boisson B, Loussert C, Thiberge S, Lacroix C, Gueirard P, Ménard R. Clonal Conditional Mutagenesis in Malaria Parasites. Cell Host Microbe 2009; 5:386-96. [DOI: 10.1016/j.chom.2009.03.008] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2008] [Revised: 02/20/2009] [Accepted: 03/27/2009] [Indexed: 11/26/2022]
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81
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Production of a reporter transgenic pig for monitoring Cre recombinase activity. Biochem Biophys Res Commun 2009; 382:232-5. [PMID: 19268654 DOI: 10.1016/j.bbrc.2009.02.146] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Accepted: 02/26/2009] [Indexed: 11/23/2022]
Abstract
The pig is thought to be the most suitable non-human source of organs for xenotransplantation and is widely used as a model of human disease. Using pigs as disease models requires the design of conditional Cre recombinase-loxP gene modifications, which, in turn, requires a Cre-expressing pig with defined patterns of expression controlled by the use of a tissue-specific promoter. In order to monitor Cre recombinant expression in vivo, it is important to create a reporter strain. We have generated reporter a pig that is based on a single vector that drives the ubiquitous expression of the enhanced green fluorescent protein (EGFP). The EGFP gene is expressed only after Cre-mediated excision of loxP-flanked stop sequences. These reporter transgenic pigs will be of great value for monitoring Cre recombinase activity in vivo.
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82
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Abstract
Baculovirus is a promising gene delivery vector but its widespread application is impeded as it only mediates transient transgene expression in mammalian cells. To prolong the expression, we developed a dual baculovirus system whereby one baculovirus expressed FLP recombinase while the other harbored an Frt-flanking cassette encompassing the transgene and oriP/EBNA1 derived from Epstein-Barr virus. After cotransduction of cells, the expressed FLP cleaved the Frt-flanking cassette off the baculovirus genome and catalyzed circular episome formation, then oriP/EBNA1 within the cassette enabled the self-replication of episomes. The excision/recombination efficiency was remarkably enhanced by sodium butyrate, reaching 75% in human embryonic kidney-293 (HEK293) cells, 85% in baby-hamster kidney (BHK) cells, 77% in primary chondrocytes, and 48% in mesenchymal stem cells (MSCs). The hybrid baculovirus substantially prolonged the transgene expression to approximately 48 days without selection and >63 days with selection, thanks to the maintenance of replicons and transgene transcription. In contrast to the replicating episomes, the baculovirus genome was rapidly degraded. Furthermore, an osteoinductive growth factor gene was efficiently delivered into MSCs using this system, which not only prolonged the growth factor expression but also potentiated the osteogenesis of MSCs. These data collectively implicate the potential of this hybrid baculovirus system in gene therapy applications necessitating sustained transgene expression.
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83
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Djukanovic V, Lenderts B, Bidney D, Lyznik LA. A Cre::FLP fusion protein recombines FRT or loxP sites in transgenic maize plants. PLANT BIOTECHNOLOGY JOURNAL 2008; 6:770-781. [PMID: 18627532 DOI: 10.1111/j.1467-7652.2008.00357.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The coding sequences of Cre (site-specific recombinase from bacteriophage P1) and FLP (yeast 2-microm plasmid site-specific recombinase) were fused in frame to produce a novel, dual-function, site-specific recombinase gene. Transgenic maize plants containing the Cre::FLP fusion expression vector were crossed to transgenic plants containing either the loxP or FRT excision substrate. Complete and precise excisions of chromosomal fragments flanked by the respective target sites were observed in the F1 and F2 progeny plants. The episomal DNA recombination products were frequently lost. Non-recombined FRT substrates found in the F1 plants were recovered in the F2 generation after the Cre::FLP gene segregated out. They produced the recombination products in the F3 generation when crossed back to the FLP-expressing plants. These observations may indicate that the efficiency of site-specific recombination is affected by the plant developmental stage, with site-specific recombination being more prevalent in developing embryos. The Cre::FLP fusion protein was also tested for excisions catalysed by Cre. Excisions were identified in the F1 plants and verified in the F2 plants by polymerase chain reaction and Southern blotting. Both components of the fusion protein (FLP and Cre) were functional and acted with similar efficiency. The crossing strategy proved to be suitable for the genetic engineering of maize using the FLP or Cre site-specific recombination system.
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Affiliation(s)
- Vesna Djukanovic
- Pioneer Hi-Bred International, A DuPont Business, Research Center, 7300 NW 62nd Avenue, Johnston, IA 50131-1004, USA
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84
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Abstract
We present a two-part system for conditional FLP-out of FRT-flanked sequences in Caenorhabditis elegans to control gene activity in a spatially and/or temporally regulated manner. Using reporters, we assess the system for efficacy and demonstrate its use as a cell lineage marking tool. In addition, we construct and test a dominant-negative form of hlh-12, a gene that encodes a basic helix-loop-helix (bHLH) transcription factor required for proper distal tip cell (DTC) migration. We show that this allele can be conditionally expressed from a heat-inducible FLP recombinase and can interfere with DTC migration. Using the same DTC assay, we conditionally express an hlh-12 RNAi-hairpin and induce the DTC migration defect. Finally, we introduce a set of traditional and Gateway-compatible vectors to facilitate construction of plasmids for this technology using any promoter, reporter, and gene/hairpin of interest.
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85
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Hadjantonakis AK, Pirity M, Nagy A. Cre recombinase mediated alterations of the mouse genome using embryonic stem cells. Methods Mol Biol 2008; 461:111-32. [PMID: 19030793 PMCID: PMC2883169 DOI: 10.1007/978-1-60327-483-8_8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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86
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Affiliation(s)
- Susan M Dymecki
- Department of Genetics, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, USA.
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87
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Mishina M, Sakimura K. Conditional gene targeting on the pure C57BL/6 genetic background. Neurosci Res 2007; 58:105-12. [PMID: 17298852 DOI: 10.1016/j.neures.2007.01.004] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2006] [Accepted: 01/09/2007] [Indexed: 01/14/2023]
Abstract
Brain functions are the products of dynamic interactions between multiple genes and environments. Accordingly, there are large differences among mouse strains at the behavioral and neurobiological levels. Therefore, it is crucial to manipulate genes on the same and homogenous genetic background and then to analyze and compare the phenotypes of various genetically modified mice. Furthermore, a conditional gene targeting to restrict the gene knockout to specific cells and time is a powerful tool to investigate the molecular basis of higher brain functions such as learning and memory. We have developed a system employing Cre-progesterone receptor fusion recombinase for temporal regulation of gene targeting and Flp/frt recombination system for elimination of marker genes. Importantly, both the recombinase lines and target mice have been produced with embryonic stem cells derived from the C57BL/6 strain suitable for brain function analysis. Thus, we have established an inducible and neuron-specific gene targeting system on the pure C57BL/6 genetic background.
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Affiliation(s)
- Masayoshi Mishina
- Department of Molecular Neurobiology and Pharmacology, Graduate School of Medicine, University of Tokyo, Tokyo 113-0033, Japan.
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88
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Schnütgen F, Ghyselinck NB. Adopting the good reFLEXes when generating conditional alterations in the mouse genome. Transgenic Res 2007; 16:405-13. [PMID: 17415672 DOI: 10.1007/s11248-007-9089-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2007] [Accepted: 02/28/2007] [Indexed: 12/24/2022]
Abstract
Major advances have been made in the use of the Cre/loxP system for conditional gene targeting in the mouse. By combining the ability of Cre recombinase to invert or excise a DNA fragment, depending upon the orientation of the flanking loxP sites, and the use of wild-type loxP and variant lox511 sites, we devised an efficient and reliable Cre-mediated genetic switch, called FLEX, through which expression of a given gene can be turned off, while expression of another one can be simultaneously turned on. We discuss how this innovative, flexible and powerful approach, which virtually adapts to any kind of site-specific recombinase (e.g., Cre and Flp recombinases), can be used to easily generate, even at high throughput and genome wide scale, many genetic modifications in a conditional manner, including those which were considered as difficult or impossible to achieve.
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Affiliation(s)
- Frank Schnütgen
- Department of Molecular Haematology, University of Frankfurt Medical School, Theodor Stern Kai 7, Frankfurt am Main, Germany
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89
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Abstract
In the last decade, site-specific recombinases (SSRs), such as Cre and Flp, have emerged as indispensable tools for the precise in vivo manipulation of the mouse genome. It is now feasible to control, in space and time, the onset of gene knockouts in almost any tissue of the mouse, thus greatly facilitating the creation of sophisticated animal models for human disease and drug development. This review describes the basic principles and current status of the SSR technology, with a focus on strategies for conditional somatic mutagenesis using the Cre/lox system and ligand-activated Cre recombinases. Practical hints for generating and analysing conditional mouse mutants will be given and exciting novel applications of the SSR technology will be discussed, such as cell fate mapping and the combined use of Cre, Flp and other biotechnological tools. It will be shown how genetic manipulation of the mouse by site-specific recombination can provide new solutions to old problems in the analysis of human physiology and pathophysiology and how it can be employed for drug discovery and development.
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Affiliation(s)
- R Feil
- Interfakultäres Institut für Biochemie, Universität Tübingen, Hoppe-Seyler-Str. 4, 72076 Tübingen, Germany.
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90
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Sinclair GB, Jevon G, Colobong KE, Randall DR, Choy FYM, Clarke LA. Generation of a conditional knockout of murine glucocerebrosidase: utility for the study of Gaucher disease. Mol Genet Metab 2007; 90:148-56. [PMID: 17079175 DOI: 10.1016/j.ymgme.2006.09.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2006] [Revised: 09/20/2006] [Accepted: 09/20/2006] [Indexed: 11/25/2022]
Abstract
Gaucher disease is a disorder of sphingolipid metabolism resulting from an inherited deficiency of the lysosomal hydrolase glucocerebrosidase. Affected individuals present with a spectrum of clinical symptoms ranging from hepatosplenomegaly, haematological abnormalities, and bone pain in type 1 disease, to severe neurodegeneration and premature death in types 2 and 3 disease. Although the basic biochemical defect is well characterized, there remains a poor understanding of the underlying pathophysiology of disease. In vitro studies suggest that macrophage glucocerebroside storage leads to tissue dysfunction through complex mechanisms involving altered intracellular calcium homeostasis and apoptosis. In order to study the pathogenic roles of these complex interactions, a viable animal model for Gaucher disease is needed. The complexity of this single gene disorder has been emphasized by the varied results of previous murine Gaucher models, ranging from perinatal lethality to phenotypically and biochemically asymptomatic animals. Recognizing the need to modulate the biochemical phenotype in mice to produce a relevant model, we have created a murine strain with key exons of the glucocerebrosidase gene flanked by loxP sites. We show that expression of Cre-recombinase in cells of hematopoietic and endothelial origin results in deficiency of glucocerebrosidase in the liver, spleen, bone marrow, and peripheral white cells. Glucocerebroside storage in this model leads to progressive splenomegaly with Gaucher cell infiltration and modest storage in the liver by 26 weeks of age. These results indicate the utility of this loxP GBA targeted murine strain for understanding the complex pathophysiology of Gaucher disease.
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Affiliation(s)
- Graham B Sinclair
- Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, 950 W28th Ave. Vancouver, BC, Canada V5Z 4H4
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91
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Raymond CS, Soriano P. High-efficiency FLP and PhiC31 site-specific recombination in mammalian cells. PLoS One 2007; 2:e162. [PMID: 17225864 PMCID: PMC1764711 DOI: 10.1371/journal.pone.0000162] [Citation(s) in RCA: 291] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2006] [Accepted: 12/19/2006] [Indexed: 01/01/2023] Open
Abstract
DNA site-specific recombinases (SSRs) such as Cre, FLPe, and φC31, are powerful tools for analyzing gene function in vertebrates. While the availability of multiple high-efficiency SSRs would facilitate a wide array of genomic engineering possibilities, efficient recombination in mammalian cells has only been observed with Cre recombinase. Here we report the de novo synthesis of mouse codon-optimized FLP (FLPo) and ΦC31 (ΦC31o) SSRs, which result in recombination efficiencies similar to Cre.
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92
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Sarov M, Schneider S, Pozniakovski A, Roguev A, Ernst S, Zhang Y, Hyman AA, Stewart AF. A recombineering pipeline for functional genomics applied to Caenorhabditis elegans. Nat Methods 2006; 3:839-44. [PMID: 16990816 DOI: 10.1038/nmeth933] [Citation(s) in RCA: 159] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2006] [Accepted: 08/07/2006] [Indexed: 12/28/2022]
Abstract
We present a new concept in DNA engineering based on a pipeline of serial recombineering steps in liquid culture. This approach is fast, straightforward and facilitates simultaneous processing of multiple samples in parallel. We validated the approach by generating green fluorescent protein (GFP)-tagged transgenes from Caenorhabditis briggsae genomic clones in a multistep pipeline that takes only 4 d. The transgenes were engineered with minimal disturbance to the natural genomic context so that the correct level and pattern of expression will be secured after transgenesis. An example transgene for the C. briggsae ortholog of lin-59 was used for ballistic transformation in Caenorhabditis elegans. We show that the cross-species transgene is correctly expressed and rescues RNA interference (RNAi)-mediated knockdown of the endogenous C. elegans gene. The strategy that we describe adapts the power of recombineering in Escherichia coli for fluent DNA engineering to a format that can be directly scaled up for genomic projects.
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Affiliation(s)
- Mihail Sarov
- Dresden University of Technology, BioInnovations Centre, Genomics Department, Tatzberg 47, 01307 Dresden, Germany
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93
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Recommended Method for Chromosome Exploitation: RMCE-based Cassette-exchange Systems in Animal Cell Biotechnology. Cytotechnology 2006; 50:93-108. [PMID: 19003073 DOI: 10.1007/s10616-006-6550-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2006] [Accepted: 01/06/2006] [Indexed: 01/26/2023] Open
Abstract
The availability of site-specific recombinases has revolutionized the rational construction of cell lines with predictable properties. Early efforts were directed to providing pre-characterized genomic loci with a single recombinase target site that served as an address for the integration of vectors carrying a compatible tag. Efficient procedures of this type had to await recombinases like PhiC31, which recombine attP and attB target sites in a one-way reaction - at least in the cellular environment of the higher eukaryotic cell. Still these procedures lead to the co-introduction of prokaryotic vector sequences that are known to cause epigenetic silencing. This review illuminates the actual status of the more advanced recombinase-mediated cassette exchange (RMCE) techniques that have been developed for the major members of site-specific recombinases (SR), Flp, Cre and PhiC31. In RMCE the genomic address consists of a set of heterospecific recombinase target (RT-) sites permitting the exchange of the intervening sequence for the gene of interest (GOI), as part of a similar cassette. This process locks the GOI in place and it is 'clean' in the sense that it does not co-introduce prokaryotic vector parts nor does it leave behind a selection marker.
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94
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Wang J, Sarov M, Rientjes J, Fu J, Hollak H, Kranz H, Xie W, Stewart AF, Zhang Y. An improved recombineering approach by adding RecA to lambda Red recombination. Mol Biotechnol 2006; 32:43-53. [PMID: 16382181 DOI: 10.1385/mb:32:1:043] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Recombineering is the use of homologous recombination in Escherichia coli for DNA engineering. Of several approaches, use of the lambda phage Red operon is emerging as the most reliable and flexible. The Red operon includes three components: Redalpha, a 5' to 3' exonuclease, Redbeta, an annealing protein, and Redgamma, an inhibitor of the major E. coli exonuclease and recombination complex, RecBCD. Most E. coli cloning hosts are recA deficient to eliminate recombination and therefore enhance the stability of cloned DNAs. However, loss of RecA also impairs general cellular integrity. Here we report that transient RecA co-expression enhances the total number of successful recombinations in bacterial artificial chromosomes (BACs), mostly because the E. coli host is more able to survive the stresses of DNA transformation procedures. We combined this practical improvement with the advantages of a temperature-sensitive version of the low copy pSC101 plasmid to develop a protocol that is convenient and more efficient than any recombineering procedure, for use of either double- or single-stranded DNA, published to date.
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Affiliation(s)
- Junping Wang
- Gene Bridges GmbH, BioInnovationsZentrum Dresden, Tatzberg 47-51, 01307 Dresden, Germany
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95
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Tian Y, James S, Zuo J, Fritzsch B, Beisel KW. Conditional and inducible gene recombineering in the mouse inner ear. Brain Res 2006; 1091:243-54. [PMID: 16488403 PMCID: PMC3901521 DOI: 10.1016/j.brainres.2006.01.040] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2005] [Revised: 12/30/2005] [Accepted: 01/05/2006] [Indexed: 12/21/2022]
Abstract
Genetically engineered mice have greatly improved our understanding of gene functions and disease mechanisms. Nevertheless, the traditional knock-out approach has limitations in the overall viability of mutants. The application of the Cre/loxP system in the inner ear can help bypass this difficulty by generation of conditional gene recombineering. However, to do so requires an expression system that allows ear-specific temporally inducible, gene abrogation of one or more of the increasingly available floxed genes. To date, three approaches have been successfully used to create murine inner ear-specific Cre lines: conventional transgenesis, BAC transgenesis, and gene knock-in. Unfortunately, timing of conditional Cre activity does not extend beyond the regulatory range of the gene controlling Cre expression. Rectification of this problem requires the generation of tamoxifen or tetracycline inducible systems in the inner ear. Examination of integrase expression at different loci will facilitate studies on the expression of exogenous transgenes. These genetic applications for the mouse genome will dramatically advance in vivo gene function studies.
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Affiliation(s)
- Yong Tian
- Department of Developmental Neurobiology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Sally James
- Department of Developmental Neurobiology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Jian Zuo
- Department of Developmental Neurobiology, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA
| | - Bernd Fritzsch
- Department of Biomedical Sciences, Creighton University, School of Medicine, 2500 California Plaza, Omaha, NE 68178, USA
| | - Kirk W. Beisel
- Department of Biomedical Sciences, Creighton University, School of Medicine, 2500 California Plaza, Omaha, NE 68178, USA
- Corresponding author: Fax: +1 402 280 2690. (K.W. Beisel)
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96
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Liu W, Xiong Y, Gossen M. Stability and homogeneity of transgene expression in isogenic cells. J Mol Med (Berl) 2005; 84:57-64. [PMID: 16328206 DOI: 10.1007/s00109-005-0711-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2005] [Accepted: 07/25/2005] [Indexed: 11/25/2022]
Abstract
Genetically engineered cells are an important tool not only for basic research applications, but also for biotechnology and molecular medicine. Among the issues yet to be solved for this technology are the consequences of randomly integrating DNA into a cell's genome. The problems encountered range from unpredictable expression levels to safety concerns. Recombinase-mediated chromosome engineering is a popular tool for generating stably transfected isogenic cell lines. Using this approach, single-copy integration of foreign DNA fragments can be achieved at predetermined chromosomal loci in the genome. We used such a technology based on the Flp/Flp recombinase target (FRT) recombination system in human 293 cells for comparative promoter studies. The expected integration patterns were obtained with high frequency. In contrast, the phenotypic characterization of expression of the integrated reporter transgene showed remarkable differences between isogenic cell lines, ranging from homogenous expression to mosaic to even complete expression silencing. As long as cell clones with homogenous expression were kept under selective conditions, their expression characteristics could be maintained over a long period. However, this desirable phenotype was progressively lost upon withdrawal of selective pressure. These results were also reflected by the expression instability of the reporter cassette originally inserted in the recipient cell line. Thus, selection for appropriate integration events that ensure reproducible and long-term gene expression has to go beyond the verification of isogenicity.
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Affiliation(s)
- Weimin Liu
- Max-Delbrück-Center for Molecular Medicine, 13125 Berlin, Germany
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97
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Kerbach S, Lörz H, Becker D. Site-specific recombination in Zea mays. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2005; 111:1608-16. [PMID: 16200415 DOI: 10.1007/s00122-005-0092-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2005] [Accepted: 08/22/2005] [Indexed: 05/04/2023]
Abstract
The elimination of marker genes after selection is recommended for the commercial use of genetically modified plants. We compared the applicability of the two site-specific recombination systems Cre/lox and Flp/FRT for marker gene elimination in maize plants. The selection marker gene pat surrounded by two identically directed lox or FRT sites was introduced into maize. Sexual crossing with plants harboring the corresponding constitutively expressed recombinase led to the precise and complete excision of the lox-flanked marker gene in the F1 progeny, whereas Flp-mediated recombination of FRT sequences occurred rarely. Further examination of site-specific integration was done by biolistic bombardment of immature embryos harboring only one lox site with a lox.uidA sequence with results indicating directed integration.
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Affiliation(s)
- S Kerbach
- Biocenter Klein Flottbek, Section Developmental Biology and Biotechnology, University of Hamburg, Ohnhorststrasse 18, 22609, Hamburg, Germany
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98
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Sorrell DA, Kolb AF. Targeted modification of mammalian genomes. Biotechnol Adv 2005; 23:431-69. [PMID: 15925473 DOI: 10.1016/j.biotechadv.2005.03.003] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2004] [Revised: 03/14/2005] [Accepted: 03/14/2005] [Indexed: 12/22/2022]
Abstract
The stable and site-specific modification of mammalian genomes has a variety of applications in biomedicine and biotechnology. Here we outline two alternative approaches that can be employed to achieve this goal: homologous recombination (HR) or site-specific recombination. Homologous recombination relies on sequence similarity (or rather identity) of a piece of DNA that is introduced into a host cell and the host genome. In most cell types, the frequency of homologous recombination is markedly lower than the frequency of random integration. Especially in somatic cells, homologous recombination is an extremely rare event. However, recent strategies involving the introduction of DNA double-strand breaks, triplex forming oligonucleotides or adeno-associated virus can increase the frequency of homologous recombination. Site-specific recombination makes use of enzymes (recombinases, transposases, integrases), which catalyse DNA strand exchange between DNA molecules that have only limited sequence homology. The recognition sites of site-specific recombinases (e.g. Cre, Flp or PhiC31 integrase) are usually 30-50 bp. In contrast, retroviral integrases only require a specific dinucleotide sequence to insert the viral cDNA into the host genome. Depending on the individual enzyme, there are either innumerable or very few potential target sites for a particular integrase/recombinase in a mammalian genome. A number of strategies have been utilised successfully to alter the site-specificity of recombinases. Therefore, site-specific recombinases provide an attractive tool for the targeted modification of mammalian genomes.
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Affiliation(s)
- David A Sorrell
- Molecular Recognition Group, Hannah Research Institute, Ayr, KA6 5HL, UK
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99
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Jahnz M, Schwille P. An ultrasensitive site-specific DNA recombination assay based on dual-color fluorescence cross-correlation spectroscopy. Nucleic Acids Res 2005; 33:e60. [PMID: 15802627 PMCID: PMC1074182 DOI: 10.1093/nar/gni060] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Site-specific exchange of genetic information is mediated by DNA recombinases, such as FLP or Cre, and has become a valuable tool in modern molecular biology. The so far low number of suitable recombinating enzymes has driven current research activities towards alteration of catalytic properties, such as thermostability or recognition sequences. However, identification and analysis of new mutants requires sensitive in vitro activity assays, which traditionally are based on gel electrophoresis. Here, we describe the development of a new sensitive DNA recombination assay based on dual-color fluorescence cross-correlation spectroscopy (DC-FCCS), which works in homogenous solution and does not require any separation step such as electrophoresis. The assay was validated with unlabeled FLP recombinase and different fluorescently labeled DNA substrates containing the FLP recognition target (FRT). This strategy fulfills all requirements for possible application in high throughput screening and engineering of new site-specific DNA recombinases starting from the FLP-FRT system, and is easily adjustable to other systems like Cre/loxP.
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Affiliation(s)
| | - Petra Schwille
- To whom correspondence should be addressed. Tel: +49 351 463 40329; Fax: +49 351 463 40342;
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100
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Roy V, Qiao J, de Campos-Lima P, Caruso M. Direct evidence for the absence of intercellular trafficking of VP22 fused to GFP or to the herpes simplex virus thymidine kinase. Gene Ther 2005; 12:169-76. [PMID: 15483667 DOI: 10.1038/sj.gt.3302394] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The treatment of solid tumors by retroviral delivery of the herpes simplex virus thymidine kinase (TK) followed by ganciclovir (GCV) treatment has so far shown only limited success in patients. One major drawback in this approach is the lack of efficient in vivo gene delivery to cancer cells. Although, the transduction of every single tumor cell is not a requirement since the bystander effect (BE) mediated by gap junctions allows the diffusion of the toxic GCV metabolites from TK-expressing cells toward untransduced cells. To render the TK/GCV approach more potent, and independent of the level of gap junctions, we have tested the efficiency of a TK mutant (TK30) fused to VP22, a herpes simplex protein that seems to be capable of intercellular trafficking. We failed to detect an increase in the BE with cells expressing VP22 fused to TK30 versus cells containing TK30 alone, and this result forced us to reinvestigate the trafficking properties of VP22. Using very sensitive Western blot and fluorescence assays, we were not able to detect the spread of VP22 fused either to TK30 or GFP. These results indicate that VP22 cannot be used as a cargo to translocate TK30 or GFP.
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Affiliation(s)
- V Roy
- Le Centre de Recherche en Cancérologie de l'Université Laval, L'Hôtel-Dieu de Québec, Centre Hospitalier Universitaire de Québec, Québec, Canada
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