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Rivera-Torres N, Kmiec EB. Genetic spell-checking: gene editing using single-stranded DNA oligonucleotides. PLANT BIOTECHNOLOGY JOURNAL 2016; 14:463-470. [PMID: 26402400 DOI: 10.1111/pbi.12473] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 08/07/2015] [Accepted: 08/12/2015] [Indexed: 06/05/2023]
Abstract
Single-stranded oligonucleotides (ssODNs) can be used to direct the exchange of a single nucleotide or the repair of a single base within the coding region of a gene in a process that is known, generically, as gene editing. These molecules are composed of either all DNA residues or a mixture of RNA and DNA bases and utilize inherent metabolic functions to execute the genetic alteration within the context of a chromosome. The mechanism of action of gene editing is now being elucidated as well as an understanding of its regulatory circuitry, work that has been particularly important in establishing a foundation for designing effective gene editing strategies in plants. Double-strand DNA breakage and the activation of the DNA damage response pathway play key roles in determining the frequency with which gene editing activity takes place. Cellular regulators respond to such damage and their action impacts the success or failure of a particular nucleotide exchange reaction. A consequence of such activation is the natural slowing of replication fork progression, which naturally creates a more open chromatin configuration, thereby increasing access of the oligonucleotide to the DNA template. Herein, how critical reaction parameters influence the effectiveness of gene editing is discussed. Functional interrelationships between DNA damage, the activation of DNA response pathways and the stalling of replication forks are presented in detail as potential targets for increasing the frequency of gene editing by ssODNs in plants and plant cells.
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Affiliation(s)
- Natalia Rivera-Torres
- Gene Editing Institute, Center for Translational Cancer Research, Helen F. Graham Cancer Center & Research Institute, Christiana Care Health System, Newark, DE, USA
| | - Eric B Kmiec
- Gene Editing Institute, Center for Translational Cancer Research, Helen F. Graham Cancer Center & Research Institute, Christiana Care Health System, Newark, DE, USA
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Somatic correction of junctional epidermolysis bullosa by a highly recombinogenic AAV variant. Mol Ther 2014; 22:725-33. [PMID: 24390279 PMCID: PMC3982486 DOI: 10.1038/mt.2013.290] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2013] [Accepted: 12/17/2013] [Indexed: 12/29/2022] Open
Abstract
Definitive correction of disease causing mutations in somatic cells by homologous recombination (HR) is an attractive therapeutic approach for the treatment of genetic diseases. However, HR-based somatic gene therapy is limited by the low efficiency of gene targeting in mammalian cells and replicative senescence of primary cells ex vivo, forcing investigators to explore alternative strategies such as retro- and lentiviral gene transfer, or genome editing in induced pluripotent stem cells. Here, we report correction of mutations at the LAMA3 locus in primary keratinocytes derived from a patient affected by recessive inherited Herlitz junctional epidermolysis bullosa (H-JEB) disorder using recombinant adenoassociated virus (rAAV)-mediated HR. We identified a highly recombinogenic AAV serotype, AAV-DJ, that mediates efficient gene targeting in keratinocytes at clinically relevant frequencies with a low rate of random integration. Targeted H-JEB patient cells were selected based on restoration of adhesion phenotype, which eliminated the need for foreign sequences in repaired cells, enhancing the clinical use and safety profile of our approach. Corrected pools of primary cells assembled functional laminin-332 heterotrimer and fully reversed the blistering phenotype both in vitro and in skin grafts. The efficient targeting of the LAMA3 locus by AAV-DJ using phenotypic selection, together with the observed low frequency of off-target events, makes AAV-DJ based somatic cell targeting a promising strategy for ex vivo therapy for this severe and often lethal epithelial disorder.
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Disterer P, Papaioannou I, Evans VC, Simons JP, Owen JS. Oligonucleotide-mediated gene editing is underestimated in cells expressing mutated green fluorescent protein and is positively associated with target protein expression. J Gene Med 2012; 14:109-19. [PMID: 22228477 DOI: 10.1002/jgm.1639] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
BACKGROUND Single-stranded DNA oligonucleotides (ssODNs) can introduce small, specific sequence alterations into genomes. Potential applications include creating disease-associated mutations in cell lines or animals, functional studies of single nucleotide polymorphisms and, ultimately, clinical therapy by correcting genetic point mutations. Here, we report feasibility studies into realizing this potential by targeting a reporter gene, mutated enhanced green fluorescent protein (mEGFP). METHODS Three mammalian cell lines, CHO, HEK293T and HepG2, expressing multiple copies of mEGFP were transfected with a 27-mer ssODN capable of restoring fluorescence. Successful cell correction was quantified by flow cytometry. RESULTS Gene editing in each isogenic cell line, as measured by percentage of green cells, correlated tightly with target protein levels, and thus gene expression. In the total population, 2.5% of CHO-mEGFP cells were successfully edited, although, remarkably, in the highest decile producing mEGFP protein, over 20% of the cells had restored green fluorescence. Gene-edited clones initially selected for green fluorescence lost EGFP expression during cell passaging, which partly reflected G2-phase cycle arrest and perhaps eventual cell death. The major cause, however, was epigenetic down-regulation; incubation with sodium butyrate or 5-aza-2'-deoxycytidine reactivated fluorescent EGFP expression and hence established that the repaired genotype was stable. CONCLUSIONS Our data establish that ssODN-mediated gene editing is underestimated in cultured mammalian cells expressing nonfluorescent mutated EGFP, because of variable expression of this mEGFP target gene in the cell population. This conclusion was endorsed by studies in HEK293T-mEGFP and HepG2-mEGFP cells. We infer that oligonucleotide-directed editing of endogenous genes is feasible, particularly for those that are transcriptionally active.
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Wang D, Shukla C, Liu X, Schoeb TR, Clarke LA, Bedwell DM, Keeling KM. Characterization of an MPS I-H knock-in mouse that carries a nonsense mutation analogous to the human IDUA-W402X mutation. Mol Genet Metab 2010; 99:62-71. [PMID: 19751987 PMCID: PMC2795040 DOI: 10.1016/j.ymgme.2009.08.002] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2009] [Revised: 08/17/2009] [Accepted: 08/17/2009] [Indexed: 02/01/2023]
Abstract
Here we report the characterization of a knock-in mouse model for the autosomal recessive disorder mucopolysaccharidosis type I-Hurler (MPS I-H), also known as Hurler syndrome. MPS I-H is the most severe form of alpha-l-iduronidase deficiency. alpha-l-iduronidase (encoded by the IDUA gene) is a lysosomal enzyme that participates in the degradation of dermatan sulfate and heparan sulfate. Using gene replacement methodology, a nucleotide change was introduced into the mouse Idua locus that resulted in a nonsense mutation at codon W392. The Idua-W392X mutation is analogous to the human IDUA-W402X mutation commonly found in MPS I-H patients. We found that the phenotype in homozygous Idua-W392X mice closely correlated with the human MPS I-H disease. Homozygous W392X mice showed no detectable alpha-l-iduronidase activity. We observed a defect in GAG degradation as evidenced by an increase in sulfated GAGs excreted in the urine and stored in multiple tissues. Histology and electron microscopy also revealed evidence of GAG storage in all tissues examined. Additional assessment revealed bone abnormalities and altered metabolism within the Idua-W392X mouse. This new mouse will provide an important tool to investigate therapeutic approaches for MPS I-H that cannot be addressed using current MPS I-H animal models.
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Affiliation(s)
- Dan Wang
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Charu Shukla
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Xiaoli Liu
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Trenton R. Schoeb
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Lorne A. Clarke
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, CA
| | - David M. Bedwell
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Kim M. Keeling
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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Breyer D, Herman P, Brandenburger A, Gheysen G, Remaut E, Soumillion P, Van Doorsselaere J, Custers R, Pauwels K, Sneyers M, Reheul D. Genetic modification through oligonucleotide-mediated mutagenesis. A GMO regulatory challenge? ACTA ACUST UNITED AC 2009; 8:57-64. [PMID: 19833073 DOI: 10.1051/ebr/2009007] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
In the European Union, the definition of a GMO is technology-based. This means that a novel organism will be regulated under the GMO regulatory framework only if it has been developed with the use of defined techniques. This approach is now challenged with the emergence of new techniques. In this paper, we describe regulatory and safety issues associated with the use of oligonucleotide-mediated mutagenesis to develop novel organisms. We present scientific arguments for not having organisms developed through this technique fall within the scope of the EU regulation on GMOs. We conclude that any political decision on this issue should be taken on the basis of a broad reflection at EU level, while avoiding discrepancies at international level.
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Affiliation(s)
- Didier Breyer
- Scientific Institute of Public Health, Division of Biosafety and Biotechnology, Brussels, Belgium.
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Wuepping M, Kenner O, Hegele H, Schwandt S, Kaufmann D. Higher efficiency of thymine-adenine clamp-modified single-stranded oligonucleotides in targeted nucleotide sequence correction is not correlated with lower intracellular degradation. Hum Gene Ther 2009; 20:283-7. [PMID: 19061415 DOI: 10.1089/hum.2008.138] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Specific single-stranded oligonucleotides can induce targeted nucleotide sequence correction in eukaryotic genes in vitro and in vivo. Our model for investigating the reasons for the low correction rates achieved by this method is the correction of a point mutation in the hypoxanthine-guanine phosphoribosyltransferase gene (hprt) in the cell line V79-151. Using single-stranded phosphorothioate-modified oligonucleotides, the correction rates of this hprt mutation were low but always reproducible. One reason for low exchange rates may be fast intracellular degradation of the oligonucleotides. Therefore we compared the exchange rates of different 3' and 5' end-modified oligonucleotides with their degradation rates. Thymine-adenine (TA) repeat (clamp)-modified oligonucleotides showed higher correction rates than those with a guanine-cytosine (GC) clamp and 5' clamps induced higher correction rates than clamps at the 3' end. Experiments on the stability of the most effective 5'-TA and 3'-TA clamp-modified oligonucleotide indicated rapid cleavage and the occurrence of shortened oligonucleotides in the presence of cytoplasmic and nuclear extracts. The phosphorothioate-modified oligonucleotides were more stable, but their correction rates were lower. We suggest that there is no direct correlation between the biological stability of the full-length oligonucleotides and the exchange rates achieved.
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Affiliation(s)
- M Wuepping
- Institute of Human Genetics, University of Ulm, Albert-Einstein-Allee 11, Ulm, Germany
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Engstrom JU, Suzuki T, Kmiec EB. Regulation of targeted gene repair by intrinsic cellular processes. Bioessays 2009; 31:159-68. [PMID: 19204988 DOI: 10.1002/bies.200800119] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Targeted gene alteration (TGA) is a strategy for correcting single base mutations in the DNA of human cells that cause inherited disorders. TGA aims to reverse a phenotype by repairing the mutant base within the chromosome itself, avoiding the introduction of exogenous genes. The process of how to accurately repair a genetic mutation is elucidated through the use of single-stranded DNA oligonucleotides (ODNs) that can enter the cell and migrate to the nucleus. These specifically designed ODNs hybridize to the target sequence and act as a beacon for nucleotide exchange. The key to this reaction is the frequency with which the base is corrected; this will determine whether the approach becomes clinically relevant or not. Over the course of the last five years, workers have been uncovering the role played by the cells in regulating the gene repair process. In this essay, we discuss how the impact of the cell on TGA has evolved through the years and illustrate ways that inherent cellular pathways could be used to enhance TGA activity. We also describe the cost to cell metabolism and survival when certain processes are altered to achieve a higher frequency of repair.
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Affiliation(s)
- Julia U Engstrom
- University of Delaware, Department of Biological Sciences, Newark, DE 19716, USA
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Shang XY, Hao DL, Wu XS, Yin WX, Guo ZC, Liu DP, Liang CC. Improvement of SSO-mediated gene repair efficiency by nonspecific oligonucleotides. Biochem Biophys Res Commun 2008; 376:74-9. [PMID: 18771655 DOI: 10.1016/j.bbrc.2008.08.119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2008] [Accepted: 08/19/2008] [Indexed: 10/21/2022]
Abstract
Targeted gene repair mediated by single-stranded DNA oligonucleotides (SSOs) is a promising method to correct the mutant gene precisely in prokaryotic and eukaryotic systems. We used a HeLa cell line, which was stably integrated with mutant enhanced green fluorescence protein gene (mEGFP) in the genome, to test the efficiency of SSO-mediated gene repair. We found that the mEGFP gene was successfully repaired by specific SSOs, but the efficiency was only approximately 0.1%. Then we synthesized a series of nonspecific oligonucleotides, which were single-stranded DNA with different lengths and no significant similarity with the SSOs. We found the efficiency of SSO-mediated gene repair was increased by 6-fold in nonspecific oligonucleotides-treated cells. And this improvement in repair frequency correlated with the doses of the nonspecific oligonucleotides, instead of the lengths. Our evidence suggested that this increased repair efficiency was achieved by the transient alterations of the cellular proteome. We also found the obvious strand bias that antisense SSOs were much more effective than sense SSOs in the repair experiments with nonspecific oligonucleotides. These results provide a fresh clue into the mechanism of SSO-mediated targeted gene repair in mammalian cells.
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Affiliation(s)
- Xi-Ying Shang
- National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences (CAMS) & Peking Union Medical College (PUMC), Department of Biochemistry, 5 Dong Dan San Tiao, Beijing 100005, PR China
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Huen MSY, Li XT, Lu LY, Watt RM, Liu DP, Huang JD. The involvement of replication in single stranded oligonucleotide-mediated gene repair. Nucleic Acids Res 2006; 34:6183-94. [PMID: 17088285 PMCID: PMC1693898 DOI: 10.1093/nar/gkl852] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Targeted gene repair mediated by single-stranded oligonucleotides (SSOs) has great potential for use in functional genomic studies and gene therapy. Genetic changes have been created using this approach in a number of prokaryotic and eukaryotic systems, including mouse embryonic stem cells. However, the underlying mechanisms remain to be fully established. In one of the current models, the ‘annealing-integration’ model, the SSO anneals to its target locus at the replication fork, serving as a primer for subsequent DNA synthesis mediated by the host replication machinery. Using a λ-Red recombination-based system in the bacterium Escherichia coli, we systematically examined several fundamental premises that form the mechanistic basis of this model. Our results provide direct evidence strongly suggesting that SSO-mediated gene repair is mechanistically linked to the process of DNA replication, and most likely involves a replication intermediate. These findings will help guide future experiments involving SSO-mediated gene repair in mammalian and prokaryotic cells, and suggest several mechanisms by which the efficiencies may be reliably and substantially increased.
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Affiliation(s)
- Michael S. Y. Huen
- Department of Biochemistry, The University of Hong Kong3/F Laboratory Block, Faculty of Medicine Building, 21 Sassoon Road, Pokfulam, Hong Kong SAR, China
| | - Xin-tian Li
- Department of Biochemistry, The University of Hong Kong3/F Laboratory Block, Faculty of Medicine Building, 21 Sassoon Road, Pokfulam, Hong Kong SAR, China
- National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences (CAMS) and Peking Union Medical College (PUMC)Beijing 100005, P.R. China
| | - Lin-Yu Lu
- Department of Biochemistry, The University of Hong Kong3/F Laboratory Block, Faculty of Medicine Building, 21 Sassoon Road, Pokfulam, Hong Kong SAR, China
| | - Rory M. Watt
- Open Laboratory of Chemical Biology, The Institute of Molecular Technology for Drug Discovery and Synthesis, Department of Chemistry, The University of Hong Kong Pokfulam RoadHong Kong SAR, China
| | - De-Pei Liu
- National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences (CAMS) and Peking Union Medical College (PUMC)Beijing 100005, P.R. China
| | - Jian-Dong Huang
- Department of Biochemistry, The University of Hong Kong3/F Laboratory Block, Faculty of Medicine Building, 21 Sassoon Road, Pokfulam, Hong Kong SAR, China
- To whom correspondence should be addressed. Tel: +852 2819 2810; Fax: +852 2855 1254;
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Current understanding of dystrophin-related muscular dystrophy and therapeutic challenges ahead. Chin Med J (Engl) 2006. [DOI: 10.1097/00029330-200608020-00011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Olsen PA, Randøl M, Luna L, Brown T, Krauss S. Genomic sequence correction by single-stranded DNA oligonucleotides: role of DNA synthesis and chemical modifications of the oligonucleotide ends. J Gene Med 2006; 7:1534-44. [PMID: 16025558 DOI: 10.1002/jgm.804] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Single-stranded oligonucleotides (ssODN) can induce site-specific genetic alterations in selected mammalian cells, but the involved mechanisms are not known. METHODS We corroborate the potential of genomic sequence correction by ssODN using chromosomally integrated mutated enhanced green fluorescent protein (mEGFP) reporter genes in CHO cell lines. The role of integration site was studied in a panel of cell clones with randomly integrated reporters and in cell lines with site-specific single copy integration of the mEGFP reporter in opposite orientations. Involvement of end modification was examined on ssODN with unprotected or phosphorothioate (PS) protected ends. Also ssODN containing octyl or hexaethylene glycol (HEG) end blocking groups were tested. The significance of DNA synthesis was investigated by cell cycle analysis and by the DNA polymerases alpha, delta and epsilon inhibitor aphidicolin. RESULTS Correction rates of up to 5% were observed upon a single transfection of ssODN. Independent of the mEGFP chromosomal integration site and of its orientation towards the replication fork, antisense ssODN were more effective than sense ssODN. When ssODN ends were blocked by either octyl or HEG groups, correction rates were reduced. Finally, we demonstrate a dependence of the process on DNA synthesis. CONCLUSIONS We show that, on a chromosomal level, the orientation of the replication fork towards the targeted locus is not central in the strand bias of ssODN-based targeted sequence correction. We demonstrate the importance of accessible ssODN ends for sequence alteration. Finally, we provide evidence for the involvement of DNA synthesis in the process.
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Affiliation(s)
- Petter Angell Olsen
- Department for Cellular and Genetic Therapy, Institute for Microbiology, Rikshospitalet, 0349 Oslo, Norway
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Sangiuolo F, Novelli G. Sequence-specific modification of mouse genomic DNA mediated by gene targeting techniques. Cytogenet Genome Res 2005; 105:435-41. [PMID: 15237231 DOI: 10.1159/000078216] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2003] [Accepted: 10/21/2003] [Indexed: 11/19/2022] Open
Abstract
The major impact of the human genome sequence is the understanding of disease etiology with deduced therapy. The completion of this project has shifted the interest from the sequencing and identification of genes to the exploration of gene function, signalling the beginning of the post-genomic era. Contrasting with the spectacular progress in the identification of many morbid genes, today therapeutic progress is still lagging behind. The goal of all gene therapy protocols is to repair the precise genetic defect without additional modification of the genome. The main strategy has traditionally been focused on the introduction of an expression system designed to express a specific protein, defective in the transfected cell. But the numerous deficiencies associated with gene augmentation have resulted in the development of alternative approaches to treat inherited and acquired genetic disorders. Among these one is represented by gene repair based on homologous recombination (HR). Simply stated, the process involves targeting the mutation in situ for gene correction and for restoration of a normal gene function. Homologous recombination is an efficient means for genomic manipulation of prokaryotes, yeast and some lower eukaryotes. By contrast, in higher eukaryotes it is less efficient than in the prokaryotic system, with non-homologous recombination being 10-50 fold higher. However, recent advances in gene targeting and novel strategies have led to the suggestion that gene correction based on HR might be used as clinical therapy for genetic disease. This site-specific gene repair approach could represent an alternative gene therapy strategy in respect to those involving the use of retroviral or lentiviral vectors to introduce therapeutic genes and linked regulatory sequences into random sites within the target cell genome. In fact, gene therapy approaches involving addition of a gene by viral or nonviral vectors often give a short duration of gene expression and are difficult to target to specific populations of cells. The purpose of this paper is to review oligonucleotide-based gene targeting technologies and their applications on modifying the mouse genome.
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Affiliation(s)
- F Sangiuolo
- Department of Biopathology and Diagnostic Imaging, Tor Vergata University, Rome, Italy
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Abstract
Alpha-1-antitrypsin (AT) deficiency was first described in the late 1960s in patients with severe pulmonary emphysema. The recognition of AT deficiency as a cause of emphysema then led to what is still the prevailing theory for the pathogenesis of emphysema, the protease-antiprotease theory. Soon it was found that AT deficiency accounted for a significant number of cases of neonatal liver disease that were previously categorized as idiopathic. We now know that AT deficiency is the most common genetic cause of neonatal liver disease and the most frequent diagnosis necessitating liver transplantation. It has also been shown to cause chronic liver disease, cryptogenic cirrhosis, and hepatocellular carcinoma in adults never previously known to have liver disease in infancy or childhood. Observations indicate that genetic traits unlinked to the AT gene or environmental factors predispose to or protect AT-deficient individuals from liver disease.
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Kenner O, Lutomska A, Speit G, Vogel W, Kaufmann D. Concurrent targeted exchange of three bases in mammalian hprt by oligonucleotides. Biochem Biophys Res Commun 2004; 321:1017-23. [PMID: 15358130 DOI: 10.1016/j.bbrc.2004.07.062] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2004] [Indexed: 11/22/2022]
Abstract
The repair of point mutations in hprt gene by single-stranded oligonucleotides represents a model to test targeted nucleotide exchange. We studied the concurrent nucleotide exchange of two or three nucleotides in the hprt deficient hamster cell line V79-151. The used oligonucleotides resulted in mismatches at two (151, 159) or three (151, 144, and 159) hprt positions. The hprt point mutation at position 151 was repaired in about 2/10(6) cells as shown by hprt sequencing in clones surviving HAT selection. The second nucleotide exchange at hprt position 159 was found in 7% of these HAT selected clones. Using oligonucleotides resulting in three mismatches, 29% of the clones showed nucleotide exchanges at the two hprt positions (151, 144) and about 4% at three positions (151, 144, and 159). These results indicate that single-stranded oligonucleotides can generate two or three nucleotide exchanges in a mammalian chromosomal gene.
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Affiliation(s)
- Oliver Kenner
- Department of Human Genetics, University of Ulm, D 89070 Ulm, Germany
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