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Grazioli S, Petris G. Synthetic genomics for curing genetic diseases. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2021; 182:477-520. [PMID: 34175051 DOI: 10.1016/bs.pmbts.2021.02.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
From the beginning of the genome sequencing era, it has become increasingly evident that genetics plays a role in all diseases, of which only a minority are single-gene disorders, the most common target of current gene therapies. However, the majority of people have some kind of health problems resulting from congenital genetic mutations (over 6000 diseases have been associated to genes, https://www.omim.org/statistics/geneMap) and most genetic disorders are rare and only incompletely understood. The vision and techniques applied to the synthesis of genomes may help to address unmet medical needs from a chromosome and genome-scale perspective. In this chapter, we address the potential therapy of genetic diseases from a different outlook, in which we no longer focus on small gene corrections but on higher-order tools for genome manipulation. These will play a crucial role in the next years, as they prelude to a much deeper understanding of the architecture of the human genome and a more accurate modeling of human diseases, offering new therapeutic opportunities.
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Affiliation(s)
| | - Gianluca Petris
- Medical Research Council Laboratory of Molecular Biology (MRC LMB), Cambridge, United Kingdom.
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2
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Marques A, Klemme S, Houben A. Evolution of Plant B Chromosome Enriched Sequences. Genes (Basel) 2018; 9:genes9100515. [PMID: 30360448 PMCID: PMC6210368 DOI: 10.3390/genes9100515] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Revised: 10/13/2018] [Accepted: 10/18/2018] [Indexed: 01/10/2023] Open
Abstract
B chromosomes are supernumerary chromosomes found in addition to the normal standard chromosomes (A chromosomes). B chromosomes are well known to accumulate several distinct types of repeated DNA elements. Although the evolution of B chromosomes has been the subject of numerous studies, the mechanisms of accumulation and evolution of repetitive sequences are not fully understood. Recently, new genomic approaches have shed light on the origin and accumulation of different classes of repetitive sequences in the process of B chromosome formation and evolution. Here we discuss the impact of repetitive sequences accumulation on the evolution of plant B chromosomes.
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Affiliation(s)
- André Marques
- Laboratory of Genetic Resources, Federal University of Alagoas, Av. Manoel Severino Barbosa, 57309-005 Arapiraca-AL, Brazil.
| | - Sonja Klemme
- Biology Centre, Czech Academy of Sciences, Institute of Plant Molecular Biology, Branišovská 31, CZ-37005 České Budějovice, Czech Republic.
| | - Andreas Houben
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Gatersleben, Germany.
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3
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Kouprina N, Petrov N, Molina O, Liskovykh M, Pesenti E, Ohzeki JI, Masumoto H, Earnshaw WC, Larionov V. Human Artificial Chromosome with Regulated Centromere: A Tool for Genome and Cancer Studies. ACS Synth Biol 2018; 7:1974-1989. [PMID: 30075081 PMCID: PMC6154217 DOI: 10.1021/acssynbio.8b00230] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Since their description in the late 1990s, Human Artificial Chromosomes (HACs) bearing functional kinetochores have been considered as promising systems for gene delivery and expression. More recently a HAC assembled from a synthetic alphoid DNA array has been exploited in studies of centromeric chromatin and in assessing the impact of different epigenetic modifications on kinetochore structure and function in human cells. This HAC was termed the alphoidtetO-HAC, as the synthetic monomers each contained a tetO sequence in place of the CENP-B box that can be targeted specifically with tetR-fusion proteins. Studies in which the kinetochore chromatin of the alphoidtetO-HAC was specifically modified, revealed that heterochromatin is incompatible with centromere function and that centromeric transcription is important for centromere assembly and maintenance. In addition, the alphoidtetO-HAC was modified to carry large gene inserts that are expressed in target cells under conditions that recapitulate the physiological regulation of endogenous loci. Importantly, the phenotypes arising from stable gene expression can be reversed when cells are "cured" of the HAC by inactivating its kinetochore in proliferating cell populations, a feature that provides a control for phenotypic changes attributed to expression of HAC-encoded genes. AlphoidtetO-HAC-based technology has also been used to develop new drug screening and assessment strategies to manipulate the CIN phenotype in cancer cells. In summary, the alphoidtetO-HAC is proving to be a versatile tool for studying human chromosome transactions and structure as well as for genome and cancer studies.
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Affiliation(s)
- Natalay Kouprina
- Developmental
Therapeutics Branch, National Cancer Institute,
NIH, Bethesda, Maryland 20892, United
States,E-mail: . Tel: +1-240-760-7325
| | - Nikolai Petrov
- Developmental
Therapeutics Branch, National Cancer Institute,
NIH, Bethesda, Maryland 20892, United
States
| | - Oscar Molina
- Josep
Carreras Leukaemia Research Institute, School of Medicine, University
of Barcelona, Casanova 143, 08036 Barcelona, Spain
| | - Mikhail Liskovykh
- Developmental
Therapeutics Branch, National Cancer Institute,
NIH, Bethesda, Maryland 20892, United
States
| | - Elisa Pesenti
- Wellcome
Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, Scotland
| | - Jun-ichirou Ohzeki
- Laboratory
of Chromosome Engineering, Department of Frontier Research and Development, Kazusa DNA Research Institute, Kisarazu, Chiba 292-0818d Japan
| | - Hiroshi Masumoto
- Laboratory
of Chromosome Engineering, Department of Frontier Research and Development, Kazusa DNA Research Institute, Kisarazu, Chiba 292-0818d Japan,E-mail: . Tel: +81-438-52-395
| | - William C. Earnshaw
- Wellcome
Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, Scotland,E-mail: . Tel: +44-(0)131-650-7101
| | - Vladimir Larionov
- Developmental
Therapeutics Branch, National Cancer Institute,
NIH, Bethesda, Maryland 20892, United
States,E-mail: . Tel: +1-240-760-7325
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4
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Katona RL. De novo formed satellite DNA-based mammalian artificial chromosomes and their possible applications. Chromosome Res 2015; 23:143-57. [DOI: 10.1007/s10577-014-9458-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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5
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Role of epigenetics in expression of recombinant proteins from mammalian cells. ACTA ACUST UNITED AC 2014. [DOI: 10.4155/pbp.14.47] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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6
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Nucleolar organization, ribosomal DNA array stability, and acrocentric chromosome integrity are linked to telomere function. PLoS One 2014; 9:e92432. [PMID: 24662969 PMCID: PMC3963894 DOI: 10.1371/journal.pone.0092432] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 02/21/2014] [Indexed: 12/16/2022] Open
Abstract
The short arms of the ten acrocentric human chromosomes share several repetitive DNAs, including ribosomal RNA genes (rDNA). The rDNA arrays correspond to nucleolar organizing regions that coalesce each cell cycle to form the nucleolus. Telomere disruption by expressing a mutant version of telomere binding protein TRF2 (dnTRF2) causes non-random acrocentric fusions, as well as large-scale nucleolar defects. The mechanisms responsible for acrocentric chromosome sensitivity to dysfunctional telomeres are unclear. In this study, we show that TRF2 normally associates with the nucleolus and rDNA. However, when telomeres are crippled by dnTRF2 or RNAi knockdown of TRF2, gross nucleolar and chromosomal changes occur. We used the controllable dnTRF2 system to precisely dissect the timing and progression of nucleolar and chromosomal instability induced by telomere dysfunction, demonstrating that nucleolar changes precede the DNA damage and morphological changes that occur at acrocentric short arms. The rDNA repeat arrays on the short arms decondense, and are coated by RNA polymerase I transcription binding factor UBF, physically linking acrocentrics to one another as they become fusogenic. These results highlight the importance of telomere function in nucleolar stability and structural integrity of acrocentric chromosomes, particularly the rDNA arrays. Telomeric stress is widely accepted to cause DNA damage at chromosome ends, but our findings suggest that it also disrupts chromosome structure beyond the telomere region, specifically within the rDNA arrays located on acrocentric chromosomes. These results have relevance for Robertsonian translocation formation in humans and mechanisms by which acrocentric-acrocentric fusions are promoted by DNA damage and repair.
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7
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Tóth A, Fodor K, Praznovszky T, Tubak V, Udvardy A, Hadlaczky G, Katona RL. Novel method to load multiple genes onto a mammalian artificial chromosome. PLoS One 2014; 9:e85565. [PMID: 24454889 PMCID: PMC3893256 DOI: 10.1371/journal.pone.0085565] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Accepted: 12/03/2013] [Indexed: 01/05/2023] Open
Abstract
Mammalian artificial chromosomes are natural chromosome-based vectors that may carry a vast amount of genetic material in terms of both size and number. They are reasonably stable and segregate well in both mitosis and meiosis. A platform artificial chromosome expression system (ACEs) was earlier described with multiple loading sites for a modified lambda-integrase enzyme. It has been shown that this ACEs is suitable for high-level industrial protein production and the treatment of a mouse model for a devastating human disorder, Krabbe's disease. ACEs-treated mutant mice carrying a therapeutic gene lived more than four times longer than untreated counterparts. This novel gene therapy method is called combined mammalian artificial chromosome-stem cell therapy. At present, this method suffers from the limitation that a new selection marker gene should be present for each therapeutic gene loaded onto the ACEs. Complex diseases require the cooperative action of several genes for treatment, but only a limited number of selection marker genes are available and there is also a risk of serious side-effects caused by the unwanted expression of these marker genes in mammalian cells, organs and organisms. We describe here a novel method to load multiple genes onto the ACEs by using only two selectable marker genes. These markers may be removed from the ACEs before therapeutic application. This novel technology could revolutionize gene therapeutic applications targeting the treatment of complex disorders and cancers. It could also speed up cell therapy by allowing researchers to engineer a chromosome with a predetermined set of genetic factors to differentiate adult stem cells, embryonic stem cells and induced pluripotent stem (iPS) cells into cell types of therapeutic value. It is also a suitable tool for the investigation of complex biochemical pathways in basic science by producing an ACEs with several genes from a signal transduction pathway of interest.
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Affiliation(s)
- Anna Tóth
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
| | - Katalin Fodor
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
| | - Tünde Praznovszky
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
| | - Vilmos Tubak
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
| | - Andor Udvardy
- Institute of Biochemistry, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
| | - Gyula Hadlaczky
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
| | - Robert L. Katona
- Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
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8
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Praznovszky T. Chromosome engineering with lambda-integrase mediated recombination system: the ACE system. Methods Mol Biol 2011; 738:141-9. [PMID: 21431725 DOI: 10.1007/978-1-61779-099-7_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Mammalian satellite DNA-based artificial chromosomes (SATACs) are unique among the mammalian artificial chromosomes. These reproducibly generated de novo chromosomes are stably maintained in different species, readily purified from the host cell's chromosomes and can be introduced into a variety of recipient cells. An artificial chromosome expression system (ACE system) has been developed on these SATACs to extend them for chromosome engineering. This system includes a Platform ACE containing multiple acceptor sites, specially designed targeting vector (ATV), and an ACE-integrase expression vector (pCXLamIntROK). Gene of interest are cloned into targeting vector (ATV), and site-specific loading of genes onto Platform ACE is facilitated by ACE-integrase mediated recombination. ACE system is suitable for multiple or subsequent loading of useful genes onto the same chromosome vector. This chapter describes the detailed procedure of chromosome engineering using the ACE system.
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Affiliation(s)
- Tünde Praznovszky
- Institute of Genetics, Biological Research Center, Hungarian Academy of Sciences, Szeged, Hungary.
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9
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Dhar MK, Kaul S, Kour J. Towards the development of better crops by genetic transformation using engineered plant chromosomes. PLANT CELL REPORTS 2011; 30:799-806. [PMID: 21249368 DOI: 10.1007/s00299-011-1001-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Revised: 01/03/2011] [Accepted: 01/04/2011] [Indexed: 05/30/2023]
Abstract
Plant Biotechnology involves manipulation of genetic material to develop better crops. Keeping in view the challenges being faced by humanity in terms of shortage of food and other resources, we need to continuously upgrade the genomic technologies and fine tune the existing methods. For efficient genetic transformation, Agrobacterium-mediated as well as direct delivery methods have been used successfully. However, these methods suffer from many disadvantages especially in terms of transfer of large genes, gene complexes and gene silencing. To overcome these problems, recently, some efforts have been made to develop genetic transformation systems based on engineered plant chromosomes called minichromosomes or plant artificial chromosomes. Two approaches namely, "top-down" or "bottom-up" have been used for minichromosomes. The former involves engineering of the existing chromosomes within a cell and the latter de novo assembling of chromosomes from the basic constituents. While some success has been achieved using these chromosomes as vectors for genetic transformation in maize, however, more studies are needed to extend this technology to crop plants. The present review attempts to trace the genesis of minichromosomes and discusses their potential of development into plant artificial chromosome vectors. The use of these vectors in genetic transformation will greatly ameliorate the food problem and help to achieve the UN Millennium development goals.
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Affiliation(s)
- Manoj K Dhar
- Plant Genomics Laboratory, School of Biotechnology, University of Jammu, Jammu, 180006, Jammu and Kashmir, India.
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10
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Greene AL, Perkins EL. Downstream bioengineering of ACE chromosomes for incorporation of site-specific recombination cassettes. Methods Mol Biol 2011; 738:127-140. [PMID: 21431724 DOI: 10.1007/978-1-61779-099-7_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Advances in mammalian artificial chromosome technology have made chromosome-based vector technology amenable to a variety of biotechnology applications including cellular protein production, genomics, and animal transgenesis. A pivotal aspect of this technology is the ability to generate artificial chromosomes de novo, transfer them to a variety of cells, and perform downstream engineering of artificial chromosomes in a tractable and rational manner. Previously, we have described an alternative artificial chromosome technology termed the ACE chromosome system, where the ACE platform chromosome contains a multitude of site-specific, recombination sites incorporated during the creation of the ACE platform chromosome. In this chapter we review a variant of the ACE chromosome technology whereby site-specific, recombination sites can be integrated into the ACE chromosome following its de novo synthesis. This variation allows insertion of user-defined, site-specific, recombination systems into an existing ACE platform chromosome. These bioengineered ACE platform chromosomes, containing user-defined recombination sites, represent an ideal circuit board to which an array of genetic factors can be plugged-in and expressed for various research and therapeutic applications.
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Affiliation(s)
- Amy L Greene
- Department of Biomedical Sciences, Mercer University School of Medicine, Savannah, GA, USA
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11
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Kennard ML. Engineered mammalian chromosomes in cellular protein production: future prospects. Methods Mol Biol 2011; 738:217-238. [PMID: 21431730 DOI: 10.1007/978-1-61779-099-7_15] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The manufacture of recombinant proteins at industrially relevant levels requires technologies that can engineer stable, high expressing cell lines rapidly, reproducibly, and with relative ease. Commonly used methods incorporate transfection of mammalian cell lines with plasmid DNA containing the gene of interest. Identifying stable high expressing transfectants is normally laborious and time consuming. To improve this process, the use of engineered chromosomes has been considered. To date, the most successful technique has been based on the artificial chromosome expression or ACE System, which consists of the targeted transfection of cells containing mammalian based artificial chromosomes with multiple recombination acceptor sites. This ACE System allows for the specific transfection of single or multiple gene copies and eliminates the need for random integration into native host chromosomes. The utility of using artificial engineered mammalian chromosomes, specifically the ACE System, is illustrated in several case studies covering the generation of CHO cell lines expressing monoclonal antibodies.
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12
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Csonka E. De novo generation of satellite DNA-based artificial chromosomes by induced large-scale amplification. Methods Mol Biol 2011; 738:111-25. [PMID: 21431723 DOI: 10.1007/978-1-61779-099-7_8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Mammalian artificial chromosomes (MACs) are engineered chromosomes with defined genetic content that can function as non-integrating vectors with large carrying capacity and stability. The large carrying capacity allows the engineering of MACs with multiple copies of the same transgene, gene complexes, and to include regulatory elements necessary for the regulated expression of transgene(s). In recent years, different approaches have been explored to generate MACs (Vos Curr Opin Genet Dev 8:351-359, 1998; Danielle et al. Trends Biotech 23:573-583, 2005; Duncan and Hadlaczky Curr Opin Biotech 18:420-424, 2007): (1) the de novo formation by centromere seeding, the "bottom-up" approach, (2) the truncation of natural chromosomes or the modification of naturally occurring minichromosomes, the "top-down" approach, and (3) the in vivo "inductive" approach. Satellite DNA-based artificial chromosomes (SATACs) generated by the in vivo "inductive" method have the potential to become an efficient tool in diverse gene technology applications such as cellular protein manufacturing (Kennard et al. BioPharm Int 20:52-59, 2007; Kennard et al. Biotechnol Bioeng 104:526-539, 2009; Kennard et al. Biotechnol Bioeng 104:540-553, 2009), transgenic animal production (Telenius et al. Chromosome Res 7:3-7, 1999; Co et al. Chromosome Res 8:183-191, 2000; Monteith et al. Methods Mol Biol 240:227-242, 2003), and ultimately a safe vector for gene therapy (Vanderbyl et al. Stem Cells 22:324-333, 2004; Vanderbyl et al. Exp Hematol 33:1470-1476, 2005; Katona et al. Cell. Mol. Life Sci 65:3830-3838, 2008). A detailed protocol for the de novo generation of satellite DNA-based artificial chromosomes (SATACs) via induced large-scale amplification is presented.
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Affiliation(s)
- Erika Csonka
- Biological Research Center, Institute of Genetics, Hungarian Academy of Sciences, Szeged, Hungary.
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13
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Abstract
B chromosomes are dispensable elements of the genome that do not recombine with the A chromosomes of the regular complement and that follow their own evolutionary pathway. Here, we survey current knowledge on the DNA/chromatin composition, origin, and drive mechanisms of B chromosomes and discuss the potential research applications of supernumerary chromosomes.
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Affiliation(s)
- Andreas Houben
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Gatersleben, Germany
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14
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Katona RL, Vanderbyl SL, Perez CF. Mammalian artificial chromosomes and clinical applications for genetic modification of stem cells: an overview. Methods Mol Biol 2011; 738:199-216. [PMID: 21431729 DOI: 10.1007/978-1-61779-099-7_14] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Modifying multipotent, self-renewing human stem cells with mammalian artificial chromosomes (MACs), present a promising clinical strategy for numerous diseases, especially ex vivo cell therapies that can benefit from constitutive or overexpression of therapeutic gene(s). MACs are nonintegrating, autonomously replicating, with the capacity to carry large cDNA or genomic sequences, which in turn enable potentially prolonged, safe, and regulated therapeutic transgene expression, and render MACs as attractive genetic vectors for "gene replacement" or for controlling differentiation pathways in progenitor cells. The status quo is that the most versatile target cell would be one that was pluripotent and self-renewing to address multiple disease target cell types, thus making multilineage stem cells, such as adult derived early progenitor cells and embryonic stem cells, as attractive universal host cells. We will describe the progress of MAC technologies, the subsequent modifications of stem cells, and discuss the establishment of MAC platform stem cell lines to facilitate proof-of-principle studies and preclinical development.
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Affiliation(s)
- Robert L Katona
- Institute of Genetics, Biological Research Center, Hungarian Academy of Sciences, Szeged, Hungary.
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15
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Kennard ML, Goosney DL, Monteith D, Zhang L, Moffat M, Fischer D, Mott J. The generation of stable, high MAb expressing CHO cell lines based on the artificial chromosome expression (ACE) technology. Biotechnol Bioeng 2009; 104:540-53. [PMID: 19557833 DOI: 10.1002/bit.22406] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The manufacture of recombinant proteins at industrially relevant levels requires technologies that can engineer stable, high expressing cell lines rapidly, reproducibly and with relative ease. Commonly used methods incorporate transfection of mammalian cell lines with plasmid DNA containing the gene of interest. Identifying stable high expressing transfectants is normally laborious and time consuming. To improve this process, the ACE System has been developed based on pre-engineered artificial chromosomes with multiple recombination acceptor sites. This system allows for the targeted transfection of single or multiple genes and eliminates the need for random integration into native host chromosomes. To illustrate the utility of the ACE System in generating stable, high expressing cell lines, CHO based candidate cell lines were generated to express a human monoclonal IgG1 antibody. Candidate cell lines were generated in under 6 months and expressed over 1 g/L and with specific productivities of up to 45 pg/cell/day under non-fed, non-optimized shake flask conditions. These candidate cell lines were shown to have stable expression of the monoclonal antibody for up to 70 days of continuous culture. The results of this study demonstrate that clonal, stable monoclonal antibody expressing CHO based cell lines can be generated by the ACE System rapidly and perform competitively with those cell lines generated by existing technologies. The ACE System, therefore, provides an attractive and practical alternative to conventional methods of cell line generation.
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16
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Kennard ML, Goosney DL, Monteith D, Roe S, Fischer D, Mott J. Auditioning of CHO host cell lines using the artificial chromosome expression (ACE) technology. Biotechnol Bioeng 2009; 104:526-39. [PMID: 19544304 DOI: 10.1002/bit.22407] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In order to maximize recombinant protein expression in mammalian cells many factors need to be considered such as transfection method, vector construction, screening techniques and culture conditions. In addition, the host cell line can have a profound effect on the protein expression. However, auditioning or directly comparing host cell lines for optimal protein expression may be difficult since most transfection methods are based on random integration of the gene of interest into the host cell genome. Thus it is not possible to determine whether differences in expression between various host cell lines are due to the phenotype of the host cell itself or genetic factors such as gene copy number or gene location. To improve cell line generation, the ACE System was developed based on pre-engineered artificial chromosomes with multiple recombination acceptor sites. This system allows for targeted transfection and has been effectively used to rapidly generate stable CHO cell lines expressing high levels of monoclonal antibody. A key feature of the ACE System is the ability to isolate and purify ACEs containing the gene(s) of interest and transfect the same ACEs into different host cell lines. This feature allows the direct auditioning of host cells since the host cells have been transfected with ACEs that contain the same number of gene copies in the same genetic environment. To investigate this audition feature, three CHO host cell lines (CHOK1SV, CHO-S and DG44) were transfected with the same ACE containing gene copies of a human monoclonal IgG1 antibody. Clonal cell lines were generated allowing a direct comparison of antibody expression and stability between the CHO host cells. Results showed that the CHOK1SV host cell line expressed antibody at levels of more than two to five times that for DG44 and CHO-S host cell lines, respectively. To confirm that the ACE itself was not responsible for the low antibody expression seen in the CHO-S based clones, the ACE was isolated and purified from these cells and transfected back into fresh CHOK1SV cells. The resulting expression of the antibody from the ACE newly transfected into CHOK1SV increased fivefold compared to its expression in CHO-S and confirmed that the differences in expression between the different CHO host cells was due to the cell phenotype rather than differences in gene copy number and/or location. These results demonstrate the utility of the ACE System in providing a rapid and direct technique for auditioning host cell lines for optimal recombinant protein expression.
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17
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Duncan A, Hadlaczky G. Chromosomal engineering. Curr Opin Biotechnol 2007; 18:420-4. [PMID: 17977711 DOI: 10.1016/j.copbio.2007.09.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2007] [Revised: 09/14/2007] [Accepted: 09/18/2007] [Indexed: 01/19/2023]
Abstract
Artificial chromosomes (ACs) are engineered chromosomes with defined genetic contents that can function as non-integrating vectors with large carrying capacity and stability. The large carrying capacity allows the engineering of ACs with multiple copies of the same transgene, gene complexes, and to include regulatory elements necessary for the regulated expression of transgene(s). Artificial chromosome based systems are composed of AC engineered to harbor and express gene(s) of interest and an appropriate recombination system for 'custom' engineering of ACs. These systems have the potential to become an efficient tool in diverse gene technology applications such as cellular protein manufacturing, transgenic animal production, and ultimately gene therapy. Recent advances in artificial chromosome technologies outline the value of these systems and justify the future research efforts to overcome the obstacles in exploring their full capabilities.
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Affiliation(s)
- Alistair Duncan
- Chromos Molecular Systems Inc., 8081 Lougheed Highway, Burnaby, BC, Canada V5A 1W9
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18
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Kato A, Zheng YZ, Auger DL, Phelps-Durr T, Bauer MJ, Lamb JC, Birchler JA. Minichromosomes derived from the B chromosome of maize. Cytogenet Genome Res 2005; 109:156-65. [PMID: 15753572 DOI: 10.1159/000082395] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2003] [Accepted: 02/20/2004] [Indexed: 11/19/2022] Open
Abstract
Fourteen minichromosomes derived from the B chromosome of maize are described. The centromeric region of the B chromosome contains a specific repetitive DNA element called the B repeat. This sequence was used to determine the transmission frequency of the different types of minichromosomes over several generations via Southern blot analysis at each generation. In general, the minichromosomes have transmission rates below the theoretical 50% frequency of a univalent chromosome. The gross structure of each minichromosome was determined using fluorescence in situ hybridization (FISH) on root tip chromosome spreads. The presence of the B centromeric repeat and of the adjacent heterochromatic knob sequences was determined for each minichromosome. In two cases, the amount of the centromeric knob repeat is increased relative to the progenitor chromosome. Other isolates have reduced or undetectable levels of the knob sequence. Potential uses of the minichromosomes are discussed.
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Affiliation(s)
- A Kato
- Division of Biological Sciences, University of Missouri, Columbia, MO 65211-7400, USA
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19
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Irvine DV, Shaw ML, Choo KHA, Saffery R. Engineering chromosomes for delivery of therapeutic genes. Trends Biotechnol 2005; 23:575-83. [PMID: 16242803 DOI: 10.1016/j.tibtech.2005.10.001] [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: 03/24/2005] [Revised: 06/03/2005] [Accepted: 10/06/2005] [Indexed: 02/02/2023]
Abstract
The ability to create fully functional human chromosome vectors represents a potentially exciting gene-delivery system for the correction of human genetic disorders with several advantages over viral delivery systems. However, for the full potential of chromosome-based gene-delivery vectors to be realized, several key obstacles must be overcome. Methods must be developed to insert therapeutic genes reliably and efficiently and to enable the stable transfer of the resulting chromosomal vectors to different therapeutic cell types. Research to achieve these outcomes continues to encounter major challenges; however recent developments have reiterated the potential of chromosome-based vectors for therapeutic gene delivery. Here we review the different strategies under development and discuss the advantages and problems associated with each.
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Affiliation(s)
- Danielle V Irvine
- Chromosome Research Group, Murdoch Childrens Research Institute, Royal Children's Hospital, Department of Paediatrics, University of Melbourne, Flemington Road, Parkville 3052, Australia
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Kostarelos K, Miller AD. Synthetic, self-assembly ABCD nanoparticles; a structural paradigm for viable synthetic non-viral vectors. Chem Soc Rev 2005; 34:970-94. [PMID: 16239997 DOI: 10.1039/b307062j] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Gene therapy research is still in trouble owing to a paucity of acceptable vector systems to deliver nucleic acids to patients for therapy. Viral vectors are efficient but may be too dangerous. Synthetic non-viral vectors are inherently safer but are currently not efficient enough to be clinically viable. The solution for gene therapy lies with improved synthetic non-viral vectors systems. This review is focused on synthetic cationic liposome/micelle-based non-viral vector systems and is a critical review written to illustrate the increasing importance of chemistry in gene therapy research. This review should be of primary interest to synthetic chemists and biomedical researchers keen to appreciate emerging technologies, but also to biological scientists who remain to be convinced about the relevance of chemistry to biology.
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Affiliation(s)
- Kostas Kostarelos
- Imperial College Genetic Therapies Centre, Department of Chemistry, Flowers Building, Imperial College London, London SW7 2AY, UK
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Bunnell BA, Izadpanah R, Ledebur HC, Perez CF. Development of mammalian artificial chromosomes for the treatment of genetic diseases: Sandhoff and Krabbe diseases. Expert Opin Biol Ther 2005; 5:195-206. [PMID: 15757381 DOI: 10.1517/14712598.5.2.195] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Mammalian artificial chromosomes (MACs) are being developed as alternatives to viral vectors for gene therapy applications, as they allow for the introduction of large payloads of genetic information in a non-integrating, autonomously replicating format. One class of MACs, the satellite DNA-based artificial chromosome expression vehicle (ACE), is uniquely suited for gene therapy applications, in that it can be generated denovo in cells, along with being easily purified and readily transferred into a variety of recipient cell lines and primary cells. To facilitate the rapid engineering of ACEs, the ACE System was developed, permitting the efficient and reproducible loading of pre-existing ACEs with DNA sequences and/or target gene(s). As a result, the ACE System and ACEs are unique and versatile platforms for ex vivo gene therapy strategies that circumvent and alleviate existing safety and delivery limitations surrounding conventional gene therapy vectors. This review will focus on the status of MAC technologies and, in particular, the application of the ACE System towards an ex vivo gene therapy treatment of lysosomal storage diseases, specifically Sandhoff (MIM #268800) and Krabbe (MIM #245200) diseases.
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Affiliation(s)
- Bruce A Bunnell
- Tulane University Health Sciences Center, Center for Gene Therapy, Department of Pharmacology, Division of Gene Therapy, Tulane National Primate Research Center, 18703 Three Rivers Road, Covington, LA 70433, USA.
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Abstract
The gene therapy approach can vary from delivering extra copies of a gene, through modifications of a genome using the properties of ribozymes or chimeraplasts, to injection of modified cells. For the treatment of genetic deficits the ultimate goal would be the repair of the mutated gene in the target tissue(s). The techniques required for such an approach are emerging, albeit slowly. Therefore, delivery of an extra copy of a normal gene in a specific vector remains the predominant approach. Moreover, this method finds wider applications in gene therapy relating to disorders other than heritable defects, e.g., malignancies, cardiovascular diseases and infections. The major and most intensive areas of research are: i) vectors and delivery methods, ii) regulation of transgene expression and iii) stability of expression. Targeting of the therapeutic gene is being accomplished by using viral vectors or non-viral delivery systems, either ex vivo or in vivo. The choice of vectors and delivery routes depends on the nature of the target cells and the required levels and stability of expression. Although there have been the first positive clinical results and significant technical achievements over the past 2 years, there are still obstacles to the development of effective clinical products and these remain largely unchanged. The most important barriers are the low levels and stability of expression and immune responses to vectors and/or gene products. The safety aspects of gene therapy have become painfully evident with the first death conclusively linked to gene therapy. The progress in AAV and lentiviral vectors, improved regulation of transgene expression and advances in stem cell technology are among the recent most exciting developments.
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Affiliation(s)
- D C Górecki
- Molecular Medicine Unit, School of Pharmacy and Biomedical Sciences, University of Portsmouth, St. Michael's Building, White Swan Road, Portsmouth, PO1 2DT, UK.
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Ekes C, Csonka E, Hadlaczky G, Cserpán I. Isolation, cloning and characterization of two major satellite DNA families of rabbit (Oryctolagus cuniculus). Gene 2005; 343:271-9. [PMID: 15588582 DOI: 10.1016/j.gene.2004.09.029] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2004] [Revised: 07/13/2004] [Accepted: 09/23/2004] [Indexed: 11/19/2022]
Abstract
We report here the isolation, cloning and characterization of two abundant centromeric satellite sequences (Rsat I and Rsat II) what are not related to each other, and that of a divergent subfamily (Rsat IIE) of rabbit (Oryctolagus cuniculus). The Rsat I monomers had a 375 base pair (bp) average length, while repeat units Rsat II and Rsat IIE were approximately 585 bp long. Variable amounts of Rsat I were detected by FISH at the centromeric region of 11 chromosome pairs of the complement. Rsat II hybridized to the centromere of 12 different chromosomes, and two of these were labeled also with the Rsat IIE probe. Two-color in situ hybridizations with the satellite probes and rDNA revealed that the NOR chromosomes carried different satellites. Rsat I was abundant on chromosome 20 and 21, but it was undetectable on chromosomes 13 and 16. Large Rsat II arrays were found on chromosomes 16, 20 and 21, but reduced amount was detected on chromosome 13. The variant Rsat IIE was prominent on chromosome 16, but was absent from the other rDNA-bearing chromosomes. The rDNA signal on chromosome 21 was localized to the 21q(ter) region, what can be a useful cytological marker in comparative cytological studies. These data show that rabbit chromosomes form at least four distinct groups based on the satellite composition of their centromeres. The differences in the chromosomal distribution of satellite families will help easy FISH identification of individual chromosomes, as well as to unveil the evolutionary history of the Leporidae karyotype.
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Affiliation(s)
- Csaba Ekes
- Institute of Genetics, Biological Research Center of the Hungarian Academy of Sciences, H-6701 Szeged, Temesvári krt. 62., P.O. Box 521, Hungary
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Girod PA, Zahn-Zabal M, Mermod N. Use of the chicken lysozyme 5′ matrix attachment region to generate high producer CHO cell lines. Biotechnol Bioeng 2005; 91:1-11. [PMID: 15889435 DOI: 10.1002/bit.20563] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Scaffold or matrix attachment region (S/MAR) genetic elements have previously been proposed to insulate transgenes from repressive effects linked to their site of integration within the host cell genome. We have evaluated their use in various stable transfection settings to increase the production of recombinant proteins such as monoclonal antibodies from Chinese hamster ovary (CHO) cell lines. Using the green fluorescent protein coding sequence, we show that S/MAR elements mediate a dual effect on the population of transfected cells. First, S/MAR elements almost fully abolish the occurrence of cell clones that express little transgene that may result from transgene integration in an unfavorable chromosomal environment. Second, they increase the overall expression of the transgene over the whole range of expression levels, allowing the detection of cells with significantly higher levels of transgene expression. An optimal setting was identified as the addition of a S/MAR element both in cis (on the transgene expression vector) and in trans (co-transfected on a separate plasmid). When used to express immunoglobulins, the S/MAR element enabled cell clones with high and stable levels of expression to be isolated following the analysis of a few cell lines generated without transgene amplification procedures.
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Affiliation(s)
- Pierre-Alain Girod
- Laboratory of Molecular Biotechnology, Center for Biotechnology UNIL-EPFL, University of Lausanne, Switzerland
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Wong LH, Saffery R, Anderson MA, Earle E, Quach JM, Stafford AJ, Fowler KJ, Choo KHA. Analysis of mitotic and expression properties of human neocentromere-based transchromosomes in mice. J Biol Chem 2004; 280:3954-62. [PMID: 15557333 DOI: 10.1074/jbc.m410047200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human neocentromeres are functional centromeres that are devoid of the typical human centromeric alpha-satellite DNA. We have transferred a 60-Mb chromosome 10-derived neocentric marker chromosome, mardel(10), and its truncated 3.5-Mb derivative, NC-MiC1, into mouse embryonic stem cell and have demonstrated a relatively high structural and mitotic stability of the transchromosomes in a heterologous genetic background. We have also produced chimeric mice carrying mardel(10) or NC-MiC1. Both transchromosomes were detected as intact episomal entities in a variety of adult chimeric mouse tissues including hemopoietic stem cells. Genes residing on these transchromosomes were expressed in the different tissues tested. Meiotic transmission of both transchromosomes in the chimeric mice was evident from the detection of DNA from these chromosomes in sperm samples. In particular, germ line transmission of NC-MiC1 was demonstrated in the F1 embryos of the chimeric mice. Variable (low in mardel(10)- or NC-MiC1-containing embryonic stem cells and chimeric mouse tissues and relatively high in NC-MiC1-containing F1 embryos) levels of missegregation of these transchromosomes were detected, suggesting that they are not optimally predisposed to full mitotic regulation in the mouse background, particularly during early embryogenesis. These results provide promising data in support of the potential use of neocentromere-based human marker chromosomes and minichromosomes as a tool for the study of centromere, neocentromere, and chromosome biology and for gene therapy studies in a mouse model system. They also highlight the need to further understand and overcome the factors that are responsible for the definable rates of instability of these transchromosomes in a mouse model.
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Affiliation(s)
- Lee H Wong
- Murdoch Childrens Research Institute & Department of Pediatrics, University of Melbourne, Royal Children's Hospital, Flemington Road, Parkville 3052, Victoria, Australia
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Vanderbyl S, MacDonald GN, Sidhu S, Gung L, Telenius A, Perez C, Perkins E. Transfer and Stable Transgene Expression of a Mammalian Artificial Chromosome into Bone Marrow-Derived Human Mesenchymal Stem Cells. Stem Cells 2004; 22:324-33. [PMID: 15153609 DOI: 10.1634/stemcells.22-3-324] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Mammalian artificial chromosomes (ACEs) transferred to autologous adult stem cells (SCs) provide a novel strategy for the ex vivo gene therapy of a variety of clinical indications. Unlike retroviral vectors, ACEs are stably maintained, autonomous, and nonintegrating. In this report we assessed the delivery efficiency of ACEs and evaluated the subsequent differentiation potential of ACE-transfected bone marrow-derived human mesenchymal stem cells (hMSCs). For this, an ACE carrying multiple copies of the red fluorescent protein (RFP) reporter gene was transferred under optimized conditions into hMSCs using standard cationic transfection reagents. RFP expression was detectable in 11% of the cells 4-5 days post-transfection. The RFP-expressing hMSCs were enriched by high-speed flow cytometry and maintained their potential to differentiate along adipogenic or osteogenic lineages. Fluorescent in situ hybridization and fluorescent microscopy demonstrated that the ACEs were stably maintained as single chromosomes and expressed the RFP transgenes in both differentiated cultures. These findings demonstrate the potential utility of ACEs for human adult SC ex vivo gene therapy.
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Affiliation(s)
- S Vanderbyl
- Chromos Molecular Systems Inc., Burnaby, British Columbia, Canada.
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Oberle V, de Jong G, Drayer JI, Hoekstra D. Efficient transfer of chromosome-based DNA constructs into mammalian cells. ACTA ACUST UNITED AC 2004; 1676:223-30. [PMID: 14984928 DOI: 10.1016/j.bbaexp.2003.12.003] [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: 07/02/2003] [Revised: 12/15/2003] [Accepted: 12/15/2003] [Indexed: 10/26/2022]
Abstract
Artificial chromosomes, engineered minichromosomes and other chromosome-based DNA constructs are promising new vectors for use in gene therapy, protein production and transgenics. However, a major drawback in the application of chromosome-based DNA is the lack of a suitable and convenient procedure for large-scale cellular introduction, which is particularly frustrated by their size (1 by 2 microm). Here we present a method to transfer Artificial Chromosome Expression systems (ACEs) into mammalian cells, which relies on a combined approach of using cationic amphiphiles and high frequency ultrasound. Thus, when cells were preincubated with liposomes consisting of the cationic lipid SAINT-2 and the phospholipid dioleoylphosphatidylethanolamine (molar ratio 1:1), followed by ultrasound, ACEs could be introduced into mammalian cells, which resulted in the expression of ACEs-harbored reporter genes, such as Green Fluorescent Protein. Depending on cell type, transfection efficiencies ranged from 12% to 53%. Interestingly, no detectable delivery occurred when cells were treated alone with either ultrasound or liposomes. Evidence is provided, based on cellular entry of differently sized beads and trypan-blue permeation, which supports a mechanism in which integration of the lipids creates unstable membrane domains, which are particularly prone to ultrasound-induced pore formation. Time- and temperature-dependent experiments indicate that these pores display a transient stability. Hence, following ultrasound, the pores disappear as a function of time as suggested by a time-window for ACEs entry, and trypan blue exclusion, 80% of the cells becoming stained immediately following ultrasound, dropping to approximately 20% after 30 min. Co-expression of different genes in conjunction with fluorescence in situ hybridization (FISH) analysis indicates that the current procedure provides a means to introduce functionally active artificial chromosomes into eukaryotic cells.
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Affiliation(s)
- Volker Oberle
- Department of Membrane Cell Biology, Faculty of Medical Sciences, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
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Abstract
Currently used vectors in human gene therapy suffer from a number of limitations with respect to safety and reproducibility. There is increasing agreement that the ideal vector for gene therapy should be completely based on chromosomal elements and behave as an independent functional unit after integration into the genome or when retained as an episome. In this review we will first discuss the chromosomal elements, such as enhancers, locus control regions, boundary elements, insulators and scaffold- or matrix-attachment regions, involved in the hierarchic regulation of mammalian gene expression and replication. These elements have been used to design vectors that behave as artificial domains when integrating into the genome. We then discuss recent progress in the use of mammalian artificial chromosomes and small circular non-viral vectors for their use as expression systems in mammalian cells.
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Affiliation(s)
- H J Lipps
- Institut für Zellbiologie, Universität Witten/Herdecke, Stockumer Strasse 10, D-58448, Witten, Germany.
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Abstract
Human artificial chromosome (HAC) technology has developed rapidly over the past four years. Recent reports show that HACs are useful gene transfer vectors in expression studies and important tools for determining human chromosome function. HACs have been used to complement gene deficiencies in human cultured cells by transfer of large genomic loci also containing the regulatory elements for appropriate expression. And, they now offer the possibility to express large human transgenes in animals, especially in mouse models of human genetic diseases.
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Affiliation(s)
- Zoia Larin
- Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK.
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Abstract
Recent advances in chromosome engineering and the potential for downstream applications in gene therapy were presented at the Artificial Chromosome Session of Genome Medicine: Gene Therapy for the Millennium in Rome, Italy in September 2001. This session concentrated primarily on the structure and function of human centromeres and the ongoing challenge of equipping human artificial chromosomes (HACs) with centromeres to ensure their mitotic stability. Advances in the 'bottom up' construction of HACs included the transfer into HT1080 cells of circular PACs containing alpha satellite DNA, and the correction of HPRT deficiency in cells using HACs. Advances in the 'top down' construction of HACs using telomere associated chromosome fragmentation in DT40 cells included the formation of HACs that are less than a megabase in size and transfer of HACs through the mouse germline. Significant progress has also been made in the use of human minichromosomes for stable trans-gene expression. While many obstacles remain towards the use of HACs for gene therapy, this session provided an optimistic outlook for future success.
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Affiliation(s)
- B R Grimes
- Department of Genetics, School of Medicine, Case Western Reserve University and University Hospital of Cleveland, Cleveland, OH 44106, USA
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Stewart S, MacDonald N, Perkins E, DeJong G, Perez C, Lindenbaum M. Retrofitting of a satellite repeat DNA-based murine artificial chromosome (ACes) to contain loxP recombination sites. Gene Ther 2002; 9:719-23. [PMID: 12032695 DOI: 10.1038/sj.gt.3301757] [Citation(s) in RCA: 14] [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
A satellite DNA-based mammalian artificial chromosome (ACes) was generated and subsequently modified by targeting of a loxP-red fluorescent protein (RFP) expression cassette via homologous recombination into a ribosomal DNA (rDNA)-containing locus. Clones containing correctly targeted ACes were identified by PCR from populations of RFP-expressing cells enriched by FACS sorting and were further characterized by fluorescent in situ hybridization. The targeted ACes maintained its ability to be purified to near homogeneity. Studies are currently underway to further characterize the functionality, carrying capacity, stability and transfectability of this modified ACes.
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Affiliation(s)
- S Stewart
- Chromos Molecular Systems Inc., Burnaby, BC, Canada
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Saffery R, Choo KHA. Strategies for engineering human chromosomes with therapeutic potential. J Gene Med 2002; 4:5-13. [PMID: 11828382 DOI: 10.1002/jgm.236] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human engineered chromosomes (HECs) have several potential advantages over currently used vectors for gene therapy applications. Firstly, there is no upper size limit to DNA that can be cloned in these vectors. Secondly, their extrachromosomal nature ensures that introduced genes are neither disruptive to, nor affected by, the genome of the host cell. Finally, being solely human in origin, HEC vectors should not evoke adverse host immunogenic responses. Recent advances have produced a variety of HECs via several different approaches. This review focuses on the current methodologies for making HEC vectors, the advantages and problems associated with each strategy, and discusses the outlook for HEC vectors as ex vivo therapeutic agents.
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Affiliation(s)
- Richard Saffery
- Murdoch Childrens Research Institute, Royal Childrens Hospital, Flemington Road, Parkville 3052, Australia.
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Abstract
We now have the capability to engineer human chromosomes that could be used to deliver therapeutic genes in gene therapy studies. These vectors have the advantages of being non-disruptive to the genome, non-immunogenic and are capable of carrying very large genes with all their regulatory sequences. What challenges lie ahead, and what future does this technology hold for gene therapy?
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Abstract
BACKGROUND Using artificial chromosome expression systems (ACes), we have developed a unique and rapid screening technique to quantify delivery of foreign DNA into cells in vitro. Delivery was measured within 24 h after transfection, using flow cytometry to detect the transfer of ACes labeled with thymidine analogue. This technique can be used to optimize delivery parameters of ACes and heterologous DNA into cells and eventually tissue. METHOD Chinese hamster ovary (CHO) cells carrying artificial chromosomes were grown in media supplemented with iododeoxyuridine (IdUrd). The 60-mb artificial chromosome was purified by flow cytometry sorting and transfected into Chinese hamster lung fibroblast cells (V79-4) or mouse connective tissue cells [LM(tk-)] using LipofectAMINE 2000trade mark, a cationic lipid, and Superfecttrade mark, a cationic dendrimer. The cells were incubated with an FITC-conjugated anti-bromodeoxyuridine (BrdUrd) antibody and analyzed by flow cytometry. IdUrd-incorporated artificial chromosome expressing green fluorescent protein (GFP) was transfected into V79-4 cells. Delivery was measured at 24 h and GFP expression was detected at 48 h. RESULTS The delivery of intact artificial chromosomes into V79-4 and LMtk- cells was detected within 2 h and up to 48 h post-transfection. Maximum delivery rates of 20% and 14% were observed using LipofectAMINE 2000 and Superfect, respectively. Flow cytometry data correlated with microscopic observations. IdUrd incorporation resulted in less quenching after staining with Hoechst 33258 and chromomycin A3 than BrdUrd incorporation. The fluorescence intensity of the FITC-conjugated anti-BrdUrd antibody was greater with IdUrd-incorporated chromosomes than with BrdUrd-incorporated chromosomes. CONCLUSION The results indicate that IdUrd-labeled artificial chromosomes can be detected 24 h after transfection. This efficient, sensitive, high-throughput detection technique is being used to evaluate and optimize other transfer technologies (e.g., electroporation and sonoporation), different delivery reagents, and protocols in a variety of cells in vitro. This work represents the first step in utilizing artificial chromosomes as nonviral vectors for gene therapy.
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Affiliation(s)
- S Vanderbyl
- Chromos Molecular Systems, Inc., Burnaby, British Columbia, Canada
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Saffery R, Wong LH, Irvine DV, Bateman MA, Griffiths B, Cutts SM, Cancilla MR, Cendron AC, Stafford AJ, Choo KH. Construction of neocentromere-based human minichromosomes by telomere-associated chromosomal truncation. Proc Natl Acad Sci U S A 2001; 98:5705-10. [PMID: 11331754 PMCID: PMC33277 DOI: 10.1073/pnas.091468498] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2000] [Indexed: 11/18/2022] Open
Abstract
Neocentromeres (NCs) are fully functional centromeres that arise ectopically in noncentromeric regions lacking alpha-satellite DNA. Using telomere-associated chromosome truncation, we have produced a series of minichromosomes (MiCs) from a mardel(10) marker chromosome containing a previously characterized human NC. These MiCs range in size from approximately 0.7 to 1.8 Mb and contain single-copy intact genomic DNA from the 10q25 region. Two of these NC-based Mi-Cs (NC-MiCs) appear circular whereas one is linear. All demonstrate stability in both structure and mitotic transmission in the absence of drug selection. Presence of a functional NC is shown by binding a host of key centromere-associated proteins. These NC-MiCs provide direct evidence for mitotic segregation function of the NC DNA and represent examples of stable mammalian MiCs lacking centromeric repeats.
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Affiliation(s)
- R Saffery
- The Murdoch Children's Research Institute, Royal Children's Hospital, Flemington Road, Melbourne 3052, Australia
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N-substituted acetonitrile inhibitors of cathepsin L. Expert Opin Ther Pat 2001. [DOI: 10.1517/13543776.11.1.149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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