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Erbs V, Lorentz R, Eisenman B, Schaeffer L, Luppi L, Lindner L, Hérault Y, Pavlovic G, Wattenhofer-Donzé M, Birling MC. Increased On-Target Rate and Risk of Concatemerization after CRISPR-Enhanced Targeting in ES Cells. Genes (Basel) 2023; 14:genes14020401. [PMID: 36833328 PMCID: PMC9957269 DOI: 10.3390/genes14020401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 01/27/2023] [Accepted: 01/31/2023] [Indexed: 02/05/2023] Open
Abstract
The French mouse clinic (Institut Clinique de la Souris; ICS) has produced more than 2000 targeting vectors for 'à la carte' mutagenesis in C57BL/6N mice. Although most of the vectors were used successfully for homologous recombination in murine embryonic stem cells (ESCs), a few have failed to target a specific locus after several attempts. We show here that co-electroporation of a CRISPR plasmid with the same targeting construct as the one that failed previously allows the systematic achievement of positive clones. A careful validation of these clones is, however, necessary as a significant number of clones (but not all) show a concatemerization of the targeting plasmid at the locus. A detailed Southern blot analysis permitted characterization of the nature of these events as standard long-range 5' and 3' PCRs were not able to distinguish between correct and incorrect alleles. We show that a simple and inexpensive PCR performed prior to ESC amplification allows detection and elimination of those clones with concatemers. Finally, although we only tested murine ESCs, our results highlight the risk of mis-validation of any genetically modified cell line (such as established lines, induced pluripotent stem cells or those used for ex vivo gene therapy) that combines the use of CRISPR/Cas9 and a circular double-stranded donor. We strongly advise the CRISPR community to perform a Southern blot with internal probes when using CRISPR to enhance homologous recombination in any cell type, including fertilized oocytes.
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Affiliation(s)
- Valérie Erbs
- CNRS, INSERM, Université de Strasbourg, CELPHEDIA, PHENOMIN-Institut Clinique de la Souris (ICS), 1 rue Laurent Fries, 67404 Illkirch Graffenstaden, France
| | - Romain Lorentz
- CNRS, INSERM, Université de Strasbourg, CELPHEDIA, PHENOMIN-Institut Clinique de la Souris (ICS), 1 rue Laurent Fries, 67404 Illkirch Graffenstaden, France
| | - Benjamin Eisenman
- CNRS, INSERM, Université de Strasbourg, CELPHEDIA, PHENOMIN-Institut Clinique de la Souris (ICS), 1 rue Laurent Fries, 67404 Illkirch Graffenstaden, France
| | - Laurence Schaeffer
- CNRS, INSERM, Université de Strasbourg, CELPHEDIA, PHENOMIN-Institut Clinique de la Souris (ICS), 1 rue Laurent Fries, 67404 Illkirch Graffenstaden, France
| | - Laurence Luppi
- CNRS, INSERM, Université de Strasbourg, CELPHEDIA, PHENOMIN-Institut Clinique de la Souris (ICS), 1 rue Laurent Fries, 67404 Illkirch Graffenstaden, France
| | - Loic Lindner
- CNRS, INSERM, Université de Strasbourg, CELPHEDIA, PHENOMIN-Institut Clinique de la Souris (ICS), 1 rue Laurent Fries, 67404 Illkirch Graffenstaden, France
| | - Yann Hérault
- CNRS, INSERM, Université de Strasbourg, CELPHEDIA, PHENOMIN-Institut Clinique de la Souris (ICS), 1 rue Laurent Fries, 67404 Illkirch Graffenstaden, France
- CNRS, INSERM, Université de Strasbourg, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Department of Translational Medicine and Neurogenetics, 1 rue Laurent Fries, 67404 Illkirch Graffenstaden, France
| | - Guillaume Pavlovic
- CNRS, INSERM, Université de Strasbourg, CELPHEDIA, PHENOMIN-Institut Clinique de la Souris (ICS), 1 rue Laurent Fries, 67404 Illkirch Graffenstaden, France
| | - Marie Wattenhofer-Donzé
- CNRS, INSERM, Université de Strasbourg, CELPHEDIA, PHENOMIN-Institut Clinique de la Souris (ICS), 1 rue Laurent Fries, 67404 Illkirch Graffenstaden, France
| | - Marie-Christine Birling
- CNRS, INSERM, Université de Strasbourg, CELPHEDIA, PHENOMIN-Institut Clinique de la Souris (ICS), 1 rue Laurent Fries, 67404 Illkirch Graffenstaden, France
- Correspondence:
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Smirnov A, Battulin N. Concatenation of Transgenic DNA: Random or Orchestrated? Genes (Basel) 2021; 12:genes12121969. [PMID: 34946918 PMCID: PMC8701086 DOI: 10.3390/genes12121969] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 12/08/2021] [Accepted: 12/09/2021] [Indexed: 12/18/2022] Open
Abstract
Generation of transgenic organisms by pronuclear microinjection has become a routine procedure. However, while the process of DNA integration in the genome is well understood, we still do not know much about the recombination between transgene molecules that happens in the first moments after DNA injection. Most of the time, injected molecules are joined together in head-to-tail tandem repeats-the so-called concatemers. In this review, we focused on the possible concatenation mechanisms and how they could be studied with genetic reporters tracking individual copies in concatemers. We also discuss various features of concatemers, including palindromic junctions and repeat-induced gene silencing (RIGS). Finally, we speculate how cooperation of DNA repair pathways creates a multicopy concatenated insert.
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Affiliation(s)
- Alexander Smirnov
- Laboratory of Developmental Genetics, Institute of Cytology and Genetics SB RAS, 630090 Novosibirsk, Russia;
| | - Nariman Battulin
- Laboratory of Developmental Genetics, Institute of Cytology and Genetics SB RAS, 630090 Novosibirsk, Russia;
- Institute of Genetic Technologies, Novosibirsk State University, 630090 Novosibirsk, Russia
- Correspondence:
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3
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Lindner L, Cayrou P, Rosahl TW, Zhou HH, Birling MC, Herault Y, Pavlovic G. Droplet digital PCR or quantitative PCR for in-depth genomic and functional validation of genetically altered rodents. Methods 2021; 191:107-119. [PMID: 33838271 DOI: 10.1016/j.ymeth.2021.04.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 03/24/2021] [Accepted: 04/01/2021] [Indexed: 12/12/2022] Open
Abstract
Gene targeting and additive (random) transgenesis have proven to be powerful technologies with which to decipher the mammalian genome. With the advent of CRISPR/Cas9 genome editing, the ability to inactivate or modify the function of a gene has become even more accessible. However, the impact of each generated modification may be different from what was initially desired. Minimal validation of mutant alleles from genetically altered (GA) rodents remains essential to guarantee the interpretation of experimental results. The protocol described here combines design strategies for genomic and functional validation of genetically modified alleles with droplet digital PCR (ddPCR) or quantitative PCR (qPCR) for target DNA or mRNA quantification. In-depth analysis of the results obtained with GA models through the analysis of target DNA and mRNA quantification is also provided, to evaluate which pitfalls can be detected using these two methods, and we propose recommendations for the characterization of different type of mutant allele (knock-out, knock-in, conditional knock-out, FLEx, IKMC model or transgenic). Our results also highlight the possibility that mRNA expression of any mutated allele can be different from what might be expected in theory or according to common assumptions. For example, mRNA analyses on knock-out lines showed that nonsense-mediated mRNA decay is generally not achieved with a critical-exon approach. Likewise, comparison of multiple conditional lines crossed with the same CreERT2 deleter showed that the inactivation outcome was very different for each conditional model. DNA quantification by ddPCR of G0 to G2 generations of transgenic rodents generated by pronuclear injection showed an unexpected variability, demonstrating that G1 generation rodents cannot be considered as established lines.
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Affiliation(s)
- Loic Lindner
- PHENOMIN-Institut Clinique de la Souris, CELPHEDIA, CNRS, INSERM, Université de Strasbourg, Illkirch-Graffenstaden, Strasbourg 67404, France
| | - Pauline Cayrou
- PHENOMIN-Institut Clinique de la Souris, CELPHEDIA, CNRS, INSERM, Université de Strasbourg, Illkirch-Graffenstaden, Strasbourg 67404, France
| | - Thomas W Rosahl
- Merck & Co., Inc., 2000 Galloping Hill Rd, Kenilworth, NJ 07033, USA
| | - Heather H Zhou
- Merck & Co., Inc., 2000 Galloping Hill Rd, Kenilworth, NJ 07033, USA
| | - Marie-Christine Birling
- PHENOMIN-Institut Clinique de la Souris, CELPHEDIA, CNRS, INSERM, Université de Strasbourg, Illkirch-Graffenstaden, Strasbourg 67404, France
| | - Yann Herault
- PHENOMIN-Institut Clinique de la Souris, CELPHEDIA, CNRS, INSERM, Université de Strasbourg, Illkirch-Graffenstaden, Strasbourg 67404, France
| | - Guillaume Pavlovic
- PHENOMIN-Institut Clinique de la Souris, CELPHEDIA, CNRS, INSERM, Université de Strasbourg, Illkirch-Graffenstaden, Strasbourg 67404, France.
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4
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Smirnov A, Fishman V, Yunusova A, Korablev A, Serova I, Skryabin BV, Rozhdestvensky TS, Battulin N. DNA barcoding reveals that injected transgenes are predominantly processed by homologous recombination in mouse zygote. Nucleic Acids Res 2020; 48:719-735. [PMID: 31740957 PMCID: PMC7145541 DOI: 10.1093/nar/gkz1085] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Revised: 10/29/2019] [Accepted: 11/05/2019] [Indexed: 12/14/2022] Open
Abstract
Mechanisms that ensure repair of double-strand DNA breaks (DSBs) are instrumental in the integration of foreign DNA into the genome of transgenic organisms. After pronuclear microinjection, exogenous DNA is usually found as a concatemer comprising multiple co-integrated transgene copies. Here, we investigated the contribution of various DSB repair pathways to the concatemer formation. We injected mouse zygotes with a pool of linear DNA molecules carrying unique barcodes at both ends and obtained 10 transgenic embryos with 1–300 transgene copies. Sequencing the barcodes allowed us to assign relative positions to the copies in concatemers and detect recombination events that occurred during integration. Cumulative analysis of approximately 1,000 integrated copies reveals that over 80% of them underwent recombination when their linear ends were processed by synthesis-dependent strand annealing (SDSA) or double-strand break repair (DSBR). We also observed evidence of double Holliday junction (dHJ) formation and crossing over during the concatemer formations. Sequencing indels at the junctions between copies shows that at least 10% of DNA molecules introduced into the zygotes are ligated by non-homologous end joining (NHEJ). Our barcoding approach, verified with Pacific Biosciences Single Molecule Real-Time (SMRT) long-range sequencing, documents high activity of homologous recombination after DNA microinjection.
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Affiliation(s)
| | - Veniamin Fishman
- Institute of Cytology and Genetics SB RAS, Novosibirsk, Russia.,Novosibirsk State University, Novosibirsk, Russia
| | | | - Alexey Korablev
- Institute of Cytology and Genetics SB RAS, Novosibirsk, Russia
| | - Irina Serova
- Institute of Cytology and Genetics SB RAS, Novosibirsk, Russia
| | - Boris V Skryabin
- Medical Faculty, Core Facility Transgenic animal and genetic engineering Models (TRAM), University of Muenster, Muenster, Germany
| | - Timofey S Rozhdestvensky
- Medical Faculty, Core Facility Transgenic animal and genetic engineering Models (TRAM), University of Muenster, Muenster, Germany
| | - Nariman Battulin
- Institute of Cytology and Genetics SB RAS, Novosibirsk, Russia.,Novosibirsk State University, Novosibirsk, Russia
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5
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Suzuki O, Koura M, Uchio-Yamada K, Sasaki M. Analysis of the transgene insertion pattern in a transgenic mouse strain using long-read sequencing. Exp Anim 2020; 69:279-286. [PMID: 32051389 PMCID: PMC7445054 DOI: 10.1538/expanim.19-0118] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Transgene insertion patterns are critical for the analysis of transgenic animals because
the influence of transgenes may change depending on the insertion pattern (such as copy
numbers and orientations of concatenations) and the insertion position in the genome. We
previously reported a genomic walking strategy to locate transgenes in the genomes of
transgenic mice (Exp. Anim. 53: 103–111, 2004) and to analyze transgene insertion patterns
(Exp. Anim. 55: 65–69, 2006). With such strategies, however, we could not determine the
copy number of transgenes or global genome modification induced by transgene insertion due
to read-length limitation. In this study, we used a long-read sequencer (MinION, Oxford
Nanopore Technologies) to overcome this limitation. We obtained 922,210 reads using MinION
with genomic DNA from a transgenic mouse strain (4C30, Proc. Jpn. Acad. Ser. B. Phys.
Biol. Sci. 87: 550–562, 2011). Among the reads, we found one 21,457-bp read containing the
transgene using a local BLAST search. Nucleotide dot plot analysis revealed that the
transgene was inserted in the genome as a tandem concatemer with an almost entire
construct (15–3,508 of 3,508 bp) and a partial fragment (4–660, 657 bp). Ensembl’s BLAST
search against the C57BL/6N genome revealed a 9,388-bp deletion at the insertion position
in the intron of the Sgcd gene, confirming that mutations such as a large
genomic deletion could occur at the time of transgene insertion. Thus, long-read
sequencers are useful tools for the analysis of transgene insertion patterns.
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Affiliation(s)
- Osamu Suzuki
- Laboratory of Animal Models for Human Diseases, National Institutes of Biomedical Innovation, Health and Nutrition,7-6-8 Saito-Asagi, Ibaraki, Ibaraki, Osaka 568-0085, Japan
| | - Minako Koura
- Laboratory of Animal Models for Human Diseases, National Institutes of Biomedical Innovation, Health and Nutrition,7-6-8 Saito-Asagi, Ibaraki, Ibaraki, Osaka 568-0085, Japan
| | - Kozue Uchio-Yamada
- Laboratory of Animal Models for Human Diseases, National Institutes of Biomedical Innovation, Health and Nutrition,7-6-8 Saito-Asagi, Ibaraki, Ibaraki, Osaka 568-0085, Japan
| | - Mitsuho Sasaki
- Laboratory of Animal Models for Human Diseases, National Institutes of Biomedical Innovation, Health and Nutrition,7-6-8 Saito-Asagi, Ibaraki, Ibaraki, Osaka 568-0085, Japan
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Muñiz Moreno MDM, Brault V, Birling MC, Pavlovic G, Herault Y. Modeling Down syndrome in animals from the early stage to the 4.0 models and next. PROGRESS IN BRAIN RESEARCH 2019; 251:91-143. [PMID: 32057313 DOI: 10.1016/bs.pbr.2019.08.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The genotype-phenotype relationship and the physiopathology of Down Syndrome (DS) have been explored in the last 20 years with more and more relevant mouse models. From the early age of transgenesis to the new CRISPR/CAS9-derived chromosomal engineering and the transchromosomic technologies, mouse models have been key to identify homologous genes or entire regions homologous to the human chromosome 21 that are necessary or sufficient to induce DS features, to investigate the complexity of the genetic interactions that are involved in DS and to explore therapeutic strategies. In this review we report the new developments made, how genomic data and new genetic tools have deeply changed our way of making models, extended our panel of animal models, and increased our understanding of the neurobiology of the disease. But even if we have made an incredible progress which promises to make DS a curable condition, we are facing new research challenges to nurture our knowledge of DS pathophysiology as a neurodevelopmental disorder with many comorbidities during ageing.
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Affiliation(s)
- Maria Del Mar Muñiz Moreno
- Université de Strasbourg, CNRS, INSERM, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France
| | - Véronique Brault
- Université de Strasbourg, CNRS, INSERM, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France
| | - Marie-Christine Birling
- Université de Strasbourg, CNRS, INSERM, PHENOMIN Institut Clinique de la Souris, Illkirch, France
| | - Guillaume Pavlovic
- Université de Strasbourg, CNRS, INSERM, PHENOMIN Institut Clinique de la Souris, Illkirch, France
| | - Yann Herault
- Université de Strasbourg, CNRS, INSERM, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France; Université de Strasbourg, CNRS, INSERM, PHENOMIN Institut Clinique de la Souris, Illkirch, France.
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7
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The high-level accumulation of n-3 polyunsaturated fatty acids in transgenic pigs harboring the n-3 fatty acid desaturase gene from Caenorhabditis briggsae. Transgenic Res 2013; 23:89-97. [PMID: 24048769 DOI: 10.1007/s11248-013-9752-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 09/06/2013] [Indexed: 10/26/2022]
Abstract
Livestock meat is generally low in n-3 polyunsaturated fatty acids (PUFAs), which are beneficial to human health. An alternative approach to increasing the levels of n-3 PUFAs in meat is to generate transgenic livestock animals. In this study, we describe the generation of cloned pigs that express the cbr-fat-1 gene from Caenorhabditis briggsae, encoding an n-3 fatty acid desaturase. Analysis of fatty acids demonstrated that the cbr-fat-1 transgenic pigs produced high levels of n-3 fatty acids from n-6 analogs; consequently, a significantly reduced ratio of n-6/n-3 fatty acids was observed. We demonstrated that the n-3 desaturase gene from C. briggsae was functionally expressed, and had a significant effect on the fatty acid composition of the transgenic pigs, which may allow the production of pork enriched in n-3 PUFAs.
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8
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Yan BW, Zhao YF, Cao WG, Li N, Gou KM. Mechanism of random integration of foreign DNA in transgenic mice. Transgenic Res 2013; 22:983-92. [PMID: 23483296 DOI: 10.1007/s11248-013-9701-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 02/28/2013] [Indexed: 11/25/2022]
Abstract
Little is known about how foreign DNA is randomly integrated into chromosomes in transgenic animals. In the current study, the insertion sites of 36 transgenic mice were mapped by thermal asymmetric interlaced PCR, and 38 junction sequences were obtained from 30 samples. Analysis of the 38 sequences revealed that 44.7 % of integration events occurred within host gene regions, including 13.2 % (5/38) in exonic regions and 31.6 % (12/38) in intronic regions. The results also revealed that all non-end side integrations of foreign DNA were mediated by short sequence homologies (microhomologies) and that the end side integrations occurred in the presence or absence of microhomologies. In addition, microhomology-mediated mechanisms were also confirmed in four transgenic Arabidopsis thaliana lines. The results indicate that foreign DNA is easily integrated into host gene regions. These results also suggest that the integration of both ends of foreign DNA follows the above-mentioned mechanism in many transgenic/transformed organisms.
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Affiliation(s)
- Bo-Wen Yan
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, 100193, People's Republic of China
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Integration, stability and expression of the E. coli phytase transgene in the Cassie line of Yorkshire Enviropig™. Transgenic Res 2012; 22:379-89. [PMID: 22948309 DOI: 10.1007/s11248-012-9646-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Accepted: 08/22/2012] [Indexed: 10/27/2022]
Abstract
The genomic structure and generational stability of the transgene carried by the Cassie (CA) line of the transgenic Enviropig™, a prospective food animal, are reported here. This transgene is composed of the Escherichia coli phytase coding sequence regulated by the mouse parotid secretory protein promoter to direct secretion of phytase in the saliva. In the CA line the transgene integrated in chromosome 4 is present as a concatemer of three copies, two in a head to tail orientation and the third in a reverse orientation 3' to the other copies with a 6 kbp deletion in the 5' promoter region. The overall size of the integrated transgene complex is 46 kbp. During integration a 66 kbp segment of the chromosome was deleted, but a BLAST search of the segment from a GenBank clone did not reveal any essential genes. The transgene integration site was stable through 9 generations analyzed. Phytase activity in the saliva was similar among 11 day old hemizygous boars and gilts and remained relatively constant through nine generations of hemizygous pigs. However, as the pigs grew there generally was a gradual decrease in activity that stabilized when pigs reached the finisher phase of growth (4-6 months old). Homozygous pigs exhibited 1.5 fold higher phytase activity (P < 0.0001) than that of hemizygous littermates. Moreover, no differential salivary phytase activity was seen in hemizygotes arising from CA-Yorkshire and CA-Duroc breed outcrosses, suggesting that expression of the transgene is unaffected by genetic background. This data demonstrates that an exogenous phytase gene can be stably transmitted and expressed in the salivary glands of a domestic food animal.
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Carlson DF, Garbe JR, Tan W, Martin MJ, Dobrinsky JR, Hackett PB, Clark KJ, Fahrenkrug SC. Strategies for selection marker-free swine transgenesis using the Sleeping Beauty transposon system. Transgenic Res 2011; 20:1125-37. [PMID: 21221779 DOI: 10.1007/s11248-010-9481-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Accepted: 12/22/2010] [Indexed: 12/11/2022]
Abstract
Swine transgenesis by pronuclear injection or cloning has traditionally relied on illegitimate recombination of DNA into the pig genome. This often results in animals containing concatemeric arrays of transgenes that complicate characterization and can impair long-term transgene stability and expression. This is inconsistent with regulatory guidance for transgenic livestock, which also discourages the use of selection markers, particularly antibiotic resistance genes. We demonstrate that the Sleeping Beauty (SB) transposon system effectively delivers monomeric, multi-copy transgenes to the pig embryo genome by pronuclear injection without markers, as well as to donor cells for founder generation by cloning. Here we show that our method of transposon-mediated transgenesis yielded 38 cloned founder pigs that altogether harbored 100 integrants for five distinct transposons encoding either human APOBEC3G or YFP-Cre. Two strategies were employed to facilitate elimination of antibiotic genes from transgenic pigs, one based on Cre-recombinase and the other by segregation of independently transposed transgenes upon breeding.
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Affiliation(s)
- Daniel F Carlson
- The Center for Genome Engineering, University of Minnesota, Minneapolis, MN 55455, USA
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11
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Shwed PS, Crosthwait J, Douglas GR, Seligy VL. Characterisation of Muta™Mouse λgt10-lacZ transgene: evidence for in vivo rearrangements. Mutagenesis 2010; 25:609-16. [PMID: 20724577 PMCID: PMC2966988 DOI: 10.1093/mutage/geq048] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The multicopy λgt10-lacZ transgene shuttle vector of Muta™Mouse serves as an important tool for genotoxicity studies. Here, we describe a model for λgt10-lacZ transgene molecular structure, based on characterisation of transgenes recovered from animals of our intramural breeding colony. Unique nucleotide sequences of the 47 513 bp monomer are reported with GenBank® assigned accession numbers. Besides defining ancestral mutations of the λgt10 used to construct the transgene and the Muta™Mouse precursor (strain 40.6), we validated the sequence integrity of key λ genes needed for the Escherichia coli host-based mutation reporting assay. Using three polymerase chain reaction (PCR)-based chromosome scanning and cloning strategies, we found five distinct in vivo transgene rearrangements, which were common to both sexes, and involved copy fusions generating ∼10 defective copies per haplotype. The transgene haplotype was estimated by Southern hybridisation and real-time–polymerase chain reaction, which yielded 29.0 ± 4.0 copies based on spleen DNA of Muta™Mouse, and a reconstructed CD2F1 genome with variable λgt10-lacZ copies. Similar analysis of commercially prepared spleen DNA from Big Blue® mouse yielded a haplotype of 23.5 ± 3.1 copies. The latter DNA is used in calibrating a commercial in vitro packaging kit for E.coli host-based mutation assays of both transgenic systems. The model for λgt10-lacZ transgene organisation, and the PCR-based methods for assessing copy number, integrity and rearrangements, potentially extends the use of Muta™Mouse construct for direct, genomic-type assays that detect the effects of clastogens and aneugens, without depending on an E.coli host, for reporting effects.
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Affiliation(s)
- Philip S Shwed
- Mechanistic Studies Division, Environmental and Radiation Health Sciences Directorate, Health Canada, Ottawa, Ontario K1A 0K9, Canada.
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12
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Yan B, Li D, Gou K. Homologous illegitimate random integration of foreign DNA into the X chromosome of a transgenic mouse line. BMC Mol Biol 2010; 11:58. [PMID: 20707910 PMCID: PMC2928235 DOI: 10.1186/1471-2199-11-58] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2010] [Accepted: 08/13/2010] [Indexed: 12/20/2022] Open
Abstract
Background It is not clear how foreign DNA molecules insert into the host genome. Recently, we have produced transgenic mice to investigate the role of the fad2 gene in the conversion of oleic acid to linoleic acid. Here we describe an integration mechanism of fad2 transgene by homologous illegitimate random integration. Results We confirmed that one fad2 line had a sole integration site on the X chromosome according to the inheritance patterns. Mapping of insertion sequences with thermal asymmetric interlaced and conventional PCR revealed that the foreign DNA was inserted into the XC1 region of the X chromosome by a homologous illegitimate replacement of an entire 45,556-bp endogenous genomic region, including the ovarian granulosa cell tumourigenesis-4 allele. For 5' and 3' junction sequences, there were very short (3-7 bp) common sequences in the AT-rich domains, which may mediate the recognition of the homologous arms between the transgene and the host genome. In addition, analysis of gene transcription indicated that the transgene was expressed in all tested fad2 tissues and that its transcription level in homozygous female tissues was about twice as high as in the heterozygous female (p < 0.05). Conclusions Taken together, the results indicated that the foreign fad2 behaved like an X-linked gene and that foreign DNA molecules were inserted into the eukaryotic genome through a homologous illegitimate random integration.
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Affiliation(s)
- Bowen Yan
- State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China
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13
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Carlson DF, Geurts AM, Garbe JR, Park CW, Rangel-Filho A, O'Grady SM, Jacob HJ, Steer CJ, Largaespada DA, Fahrenkrug SC. Efficient mammalian germline transgenesis by cis-enhanced Sleeping Beauty transposition. Transgenic Res 2010; 20:29-45. [PMID: 20352328 DOI: 10.1007/s11248-010-9386-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2009] [Accepted: 03/11/2010] [Indexed: 01/18/2023]
Abstract
Heightened interest in relevant models for human disease increases the need for improved methods for germline transgenesis. We describe a significant improvement in the creation of transgenic laboratory mice and rats by chemical modification of Sleeping Beauty transposons. Germline transgenesis in mice and rats was significantly enhanced by in vitro cytosine-phosphodiester-guanine methylation of transposons prior to injection. Heritability of transgene alleles was also greater from founder mice generated with methylated versus non-methylated transposon. The artificial methylation was reprogrammed in the early embryo, leading to founders that express the transgenes. We also noted differences in transgene insertion number and structure (single-insert versus concatemer) based on the influence of methylation and plasmid conformation (linear versus supercoiled), with supercoiled substrate resulting in efficient transpositional transgenesis (TnT) with near elimination of concatemer insertion. Combined, these substrate modifications resulted in increases in both the frequency of transgenic founders and the number of transgenes per founder, significantly elevating the number of potential transgenic lines. Given its simplicity, versatility and high efficiency, TnT with enhanced Sleeping Beauty components represents a compelling non-viral approach to modifying the mammalian germline.
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14
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Enzymatic engineering of the porcine genome with transposons and recombinases. BMC Biotechnol 2007; 7:42. [PMID: 17640337 PMCID: PMC1939997 DOI: 10.1186/1472-6750-7-42] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2007] [Accepted: 07/17/2007] [Indexed: 11/10/2022] Open
Abstract
Background Swine is an important agricultural commodity and biomedical model. Manipulation of the pig genome provides opportunity to improve production efficiency, enhance disease resistance, and add value to swine products. Genetic engineering can also expand the utility of pigs for modeling human disease, developing clinical treatment methodologies, or donating tissues for xenotransplantation. Realizing the full potential of pig genetic engineering requires translation of the complete repertoire of genetic tools currently employed in smaller model organisms to practical use in pigs. Results Application of transposon and recombinase technologies for manipulation of the swine genome requires characterization of their activity in pig cells. We tested four transposon systems- Sleeping Beauty, Tol2, piggyBac, and Passport in cultured porcine cells. Transposons increased the efficiency of DNA integration up to 28-fold above background and provided for precise delivery of 1 to 15 transgenes per cell. Both Cre and Flp recombinase were functional in pig cells as measured by their ability to remove a positive-negative selection cassette from 16 independent clones and over 20 independent genomic locations. We also demonstrated a Cre-dependent genetic switch capable of eliminating an intervening positive-negative selection cassette and activating GFP expression from episomal and genome-resident transposons. Conclusion We have demonstrated for the first time that transposons and recombinases are capable of mobilizing DNA into and out of the porcine genome in a precise and efficient manner. This study provides the basis for developing transposon and recombinase based tools for genetic engineering of the swine genome.
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15
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Uh M, Khattra J, Devlin RH. Transgene constructs in coho salmon (Oncorhynchus kisutch) are repeated in a head-to-tail fashion and can be integrated adjacent to horizontally-transmitted parasite DNA. Transgenic Res 2006; 15:711-27. [PMID: 16952013 DOI: 10.1007/s11248-006-9016-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2006] [Accepted: 05/19/2006] [Indexed: 11/24/2022]
Abstract
Currently, little information is available regarding the molecular organization of integrated transgenes in genetically-engineered fish. We performed a detailed structural analysis of an inserted transgene in one strain (M77) of transgenic coho salmon (Oncorhynchus kisutch) containing a salmon growth hormone gene construct (OnMTGH1). Microinjected DNA was found to have inserted into a single site in the coho salmon genome, and was organized with four complete internal copies and two partial terminal copies of the OnMTGH1 construct. All construct copies were organized in a direct-tandem (head-to-tail) repeat fashion in strain M77 and five additional strains (one also possessed a second recombinant junction fragment). For strain M77, the junctions between the transgene insert and the insertion point within the wild-type genome were cloned from strain-specific cosmid libraries and sequenced, revealing that the transgene insertion was accompanied by a deletion of 587 bp of wild-type DNA as well as a small insertion (19 bp) of unknown DNA upstream and a 14 bp direct- tandem duplication of sequence downstream. Upstream and downstream wild-type DNA sequence contained several repetitive sequence elements based on Southern blot analysis and homology to repetitive sequences in GenBank. In the downstream flank, a pseudogene sequence was also identified which has high homology to the CA membrane protein gene from Schistosoma japonicum, a parasite closely related to Sanguinicola sp. parasites which infect salmonids. Whether the presence of an inserted transgene and the presence of potentially horizontally-transmitted DNA are indicative of a genomic region with a predisposition for insertion of foreign DNA requires further study. The information derived from this transgene structure provides information useful for comparison to other transgenic organisms and for determination of the mechanism of transgene integration in lower vertebrates.
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Affiliation(s)
- Mitchell Uh
- Centre for Aquaculture and Environmental Research, Fisheries and Oceans Canada, West Vancouver, BC, Canada
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16
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Zhao X, Dang S, Liang B, Lei X, Chen Z, Wang L, Yan L, Sun H, Fu J, Fei J, Wang Z. PCR-based approaches for identification of multi-copy transgene integration sites in mouse genome. CHINESE SCIENCE BULLETIN-CHINESE 2006. [DOI: 10.1007/s11434-006-2100-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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17
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Suzuki O, Hata T, Takekawa N, Koura M, Takano K, Yamamoto Y, Noguchi Y, Uchio-Yamada K, Matsuda J. Transgene insertion pattern analysis using genomic walking in a transgenic mouse line. Exp Anim 2006; 55:65-9. [PMID: 16508214 DOI: 10.1538/expanim.55.65] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
A transgene mapping technique (Noguchi et al., Exp. Anim. 53:103-111, 2004) is described that can be used to analyze transgene integration patterns in transgenic mice. The technique was used to reveal that a transgenic mouse line (GM1-sy#116) harbored inverted and direct tandem repeats of both intact and partial pCAGGS-based transgenes in the G2 region of chromosome 1. This complicated concatenation of transgenes may have been caused by simple end-joining of DNA constructs fragmented by exposure to UV transillumination during gel-purification, and by nuclease digestion inside zygote pronuclei. The results suggest that care should be taken to avoid unwanted fragmentation during the preparation of vector constructs.
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Affiliation(s)
- Osamu Suzuki
- Department of Veterinary Science, National Institute of Infectious Diseases, Toyama, Tokyo, Japan
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18
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Yang G, Hall TC. HideNseek, a post-genome approach to locate transgenes exemplified in Arabidopsis thaliana. Bioinformatics 2005; 22:523-6. [PMID: 16357035 DOI: 10.1093/bioinformatics/btk003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
SUMMARY Determination of transgene location is essential for investigating the effects of position on transgene expression levels and facilitates cloning of the resident gene affected by insertion. Currently used PCR-based approaches for determination of transgene location are relatively complicated and often fail when the transgene is duplicated, rearranged or fragmented. HideNseek is a new bioinformatics tool that allows computation of transgene locations, provided that a suitable genomic restriction enzyme digestion profile is available. Since the new approach is not based on the terminal sequences of the transgene insert, it is less sensitive to transgene duplication, rearrangement or fragmentation. HideNseek has been tested experimentally and by in silico simulation. The experimental example provided here shows that this simple approach is feasible, permitting rapid location of transgenes with little bench work. AVAILABILITY available on request from the authors. SUPPLEMENTARY DATA HideNseek input and output examples, experimental procedures and figures showing experimental results are provided as supplementary files: Supplementary material 1, 2, 3 and Supplementary figures (Figs 1 and 2), respectively. Supplementary data is available at Bioinformatics online.
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Affiliation(s)
- Guojun Yang
- Institute of Developmental and Molecular Biology, Department of Biology, Texas A&M University, College Station, TX 77843, USA
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19
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Mielke C, Tümmler M, Schübeler D, von Hoegen I, Hauser H. Stabilized, long-term expression of heterodimeric proteins from tricistronic mRNA. Gene 2000; 254:1-8. [PMID: 10974530 DOI: 10.1016/s0378-1119(00)00294-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
A major problem in the use of recombinant mammalian cells for protein overexpression is their long-term stability, in particular, when the foreign gene product exerts a negative effect on the producer cells. We have addressed this issue and developed a vector system for the stable expression of heterodimeric recombinant proteins in mammalian cells. In this system, the two recombinant cDNAs and the puromycin-resistant gene are transcribed as a single tricistronic transcript. An efficient translation of the internal cistrons is mediated by internal ribosome entry sites between them. On the example of expression of a heterodimeric antibody fusion protein in BHK-21 cells, we show that the translational coupling of the antibody genes to the selectable marker in a tricistronic expression construct allows long-term stabilization of expression by continuous application of selection pressure. This vector system allows fast and straightforward construction of expression plasmids for the generation of producer cell lines, even for complex heterodimeric proteins with unlimited long-term stability.
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Affiliation(s)
- C Mielke
- GBF - Gesellschaft für Biotechnologische Forschung mbH, Department of Gene Regulation and Differentiation, Mascheroder Weg 1, 38124, Braunschweig, Germany
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20
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Pawlowski WP, Somers DA. Transgene inheritance in plants genetically engineered by microprojectile bombardment. Mol Biotechnol 1996; 6:17-30. [PMID: 8887358 DOI: 10.1007/bf02762320] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Microprojectile bombardment to deliver DNA into plant cells represents a major breakthrough in the development of plant transformation technologies and accordingly has resulted in transformation of numerous species considered recalcitrant to Agrobacterium- or protoplast-mediated transformation methods. This article attempts to review the current understanding of the molecular and genetic behavior of transgenes introduced by microprojectile bombardment. The characteristic features of the transgene integration pattern resulting from DNA delivery via microprojectile bombardment include integration of the full length transgene as well as rearranged copies of the introduced DNA. Copy number of both the transgene and rearranged fragments is often highly variable. Most frequently the multiple transgene copies and rearranged fragments are inherited as a single locus. However, a variable proportion of transgenic events produced by microprojectile bombardment exhibit Mendelian ratios for monogenic and digenic segregation vs events exhibiting segregation distortion. The potential mechanisms underlying these observations are discussed.
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Affiliation(s)
- W P Pawlowski
- Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul 55108, USA
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21
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McFarlane M, Wilson JB. A model for the mechanism of precise integration of a microinjected transgene. Transgenic Res 1996; 5:171-7. [PMID: 8673144 DOI: 10.1007/bf01969706] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A unique transgenic mouse line has undergone transgene integration in a very precise fashion. The phenotype displayed by mice of the line followed the predicted inheritance patterns for X-linked transgene insertion which has been confirmed. In order to investigate the mechanism of integration the DNA sequence of the transgene and cellular junctions have been determined. A comparison between wild type and transgenic mutant sequences at the site of insertion revealed that there was no loss or rearrangement of cellular DNA upon integration of the transgene. The cellular sequences at the transgene 5' and 3' joins are contiguous in the wild type. The integrant exists as a head to tail tandem dimer with minimal loss of sequence compared with the injected monomer. Analysis of the site of insertion has revealed a 5 bp homology between the 5' end of the transgene and the cellular sequences. In addition, adjacent to the site of insertion within the cellular sequences, there are several sequence motifs implicated in recombination events including a clustering of strong consensus sites of DNA topoisomerase type I and a region of homology to the human minisatellite consensus core sequence, the Escherichia coli Chi site and the meiotic recombination hotspot within the E beta gene of the murine major histocompatibility complex. This clustering of features is likely to have been factorial in the integrity of the insertion event. A model depicting the mechanism of this precise integration is proposed.
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MESH Headings
- Animals
- Base Sequence
- Cleft Palate/genetics
- DNA/genetics
- DNA Topoisomerases, Type I/metabolism
- DNA, Recombinant/genetics
- Epidermis/pathology
- Female
- Gene Conversion
- Genes, Viral
- Herpesvirus 4, Human/genetics
- Humans
- Hyperplasia
- Mice
- Mice, Inbred C57BL
- Mice, Transgenic/genetics
- Microinjections
- Models, Genetic
- Molecular Sequence Data
- Polyomavirus/genetics
- Recombination, Genetic
- Regulatory Sequences, Nucleic Acid
- Sequence Homology, Nucleic Acid
- Transgenes
- Viral Matrix Proteins/biosynthesis
- Viral Matrix Proteins/genetics
- X Chromosome/genetics
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Affiliation(s)
- M McFarlane
- Robertson Laboratory of Biotechnology, Division of Molecular Genetics, University of Glasgow, UK
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22
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Aratani Y, Andoh T, Koyama H. Effects of DNA topoisomerase inhibitors on nonhomologous and homologous recombination in mammalian cells. Mutat Res 1996; 362:181-91. [PMID: 8596537 DOI: 10.1016/0921-8777(95)00049-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
To study the involvement of DNA topoisomerases in recombination in mammalian cells, we used gene transfer assays to examine the effects of DNA topoisomerase inhibitors on nonhomologous (illegitimate) and homologous recombination. The assays were performed by transfecting adenine phosphoribosyltransferase-deficient (APRT-) CHO cells with plasmids carrying the wild-type or mutant aprt genes and by treating the cells with the inhibitors, followed by subsequent cultivation to select for APRT-positive (APRT+) colonies. Treatments with DNA topoisomerase II inhibitors such as VP-16, VM-26, ICRF-193 resulted in a 3- to 5-fold stimulation of integration of both closed-circular and linearized plasmids carrying the wild-type aprt gene into the recipient genome through nonhomologous recombination. The same treatments also increased 6- to 9-fold and 3-fold the number of APRT+ recombinant colonies that were generated by cotransfecting two closed-circular plasmids with nonoverlapping defective aprt genes and their linearized equivalents, respectively. However, this cotransfection assay involved intrinsically nonhomologous recombination processes; normalization of the frequencies by dividing them with those of the above nonhomologous recombination revealed 2-fold enhancement of homologous recombination events between the circular mutant genes but not between the linear ones. In contrast, DNA topoisomerase I inhibitor, camptothecin, showed no such effect on either recombination. From these results, we discuss the function of DNA topoisomerases on recombination in mammalian cells.
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Affiliation(s)
- Y Aratani
- Kihara Institute for Biolgical Research, Yokohama City University, Japan
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23
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Pawlik KM, Sun CW, Higgins NP, Townes TM. End joining of genomic DNA and transgene DNA in fertilized mouse eggs. Gene X 1995; 165:173-81. [PMID: 8522172 DOI: 10.1016/0378-1119(95)00519-c] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
A linear 5.2-kb HS2/beta-globin construct with an upstream KpnI terminus (4-nucleotide (nt) 3' protruding single strand, PSS) and a downstream SalI terminus (4-nt 5' PSS) was microinjected into fertilized mouse eggs. The injected DNA fragments integrated into the mouse genome primarily as a head-to-tail tandem array. Chromosome/transgene junctions were obtained from seven of eight transgenic animals. All of the junctions occurred in the proximity of a transgene KpnI end; a maximum loss of 8 nt from the transgene terminus was observed. Two of these junctions completely preserved the 4-nt KpnI 3' PSS. Transgene/transgene junctions from two animals were analyzed. SalI/KpnI junctions that completely preserved both the SalI 5' PSS and the KpnI 3' PSS were found in each animal. These are the first examples of complete nt preservation at junctions formed between a 5' PSS terminus and a 3' PSS terminus in transgenic mice. The data are consistent with the fill-in model of Thode et al. [Cell 60 (1990) 921-928] in which alignment proteins juxtapose 5' PSS and 3' PSS termini; DNA polymerase then utilizes the recessed 3'-OH of the 5' PSS terminus as a primer to synthesize DNA across the gap. This mechanism results in the formation of junctions with no loss of sequence. The results described in the present paper suggest that this mechanism may be involved in the formation of junctions in transgenic mice.
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Affiliation(s)
- K M Pawlik
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Alabama at Birmingham 35294, USA
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24
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Chen CM, Choo KB, Cheng WT. Frequent deletions and sequence aberrations at the transgene junctions of transgenic mice carrying the papillomavirus regulatory and the SV40 TAg gene sequences. Transgenic Res 1995; 4:52-9. [PMID: 7881462 DOI: 10.1007/bf01976502] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Exogenous DNA microinjected into one-cell mouse zygotes either integrates into the host genome within a short time span, or is rapidly degraded. On integration, a transgene sequence is frequently reiterated. In this report, we describe the enzymatic amplification analysis of transgene junctions of 12 transgenic mice carrying different copy numbers of the same transgene with dissimilar ends. The transgene was composed of the regulatory sequence of the type 18 human papillomavirus linked to the TAg gene of the SV40 virus. Nucleotide sequences of 36 of these junctions were also determined. Deletions were found in 33 (91.7%) of the junctions analysed. At the crossover regions, 55.6% contained short overlapping sequences of one to six nucleotides. Insertions of 2-6 extraneous nucleotides were also found in 8.3% of the transgene junctions. Within a 10-nucleotide sequence on both sides of the transgene junctions, topoisomerase I (topo I) cleavage sites, runs of homogeneous purines or pyrimidiens, alternating purine-pyrimidine tracks and (A-T)-rich sequences were found frequently. Stringent control experiments were also performed to ascertain that the observations made were not artefacts resulting from the polymerase chain reaction. Our data therefore indicate that damage had occurred quite frequently and extensively in our transgene construct. Such transgene damage may also occur to various extents in mice carrying other transgenes. Primary structure of the nucleotide sequences of the injected DNA seems to influence the process of transgene reiteration and aberration.
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Affiliation(s)
- C M Chen
- Department of Medical Research, Veterans General Hospital, Shih-Pai, Taipei, Taiwan
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25
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Allen MJ, Jeffreys AJ, Surani MA, Barton S, Norris ML, Collick A. Tandemly repeated transgenes of the human minisatellite MS32 (D1S8), with novel mouse gamma satellite integration. Nucleic Acids Res 1994; 22:2976-81. [PMID: 8065909 PMCID: PMC310264 DOI: 10.1093/nar/22.15.2976] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The human hypervariable minisatellite MS32 has a well characterised internal repeat unit array and high mutation rates have been observed at this locus. Analysis of MS32 mutants has shown that male germline mutations are polarised to one end of the array and frequently involve complex gene conversion-like events, suggesting that tandem repeat instability may be modulated by cis-acting sequences flanking the locus. In order to investigate the processes affecting MS32 mutation rate and mechanism, we have created transgenic mice harbouring an MS32 allele. Here we describe the organisation of eight transgenic insertions. Analysis of these transgenic loci by MVR-PCR and structural analysis of the junctions between mouse flanking DNA and the transgenic loci has shed light on mechanisms of integration and rearrangement of the tandem repeated transgenes. Sequence analysis of the mouse DNA flanking these transgenes has shown that 5 of the 8 insertions have integrated into mouse gamma satellite repeated sequence. This suggests a non-random integration of the MS32 transgene construct into the mouse genome.
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Affiliation(s)
- M J Allen
- Department of Genetics, University of Leicester, UK
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26
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Hamada T, Sasaki H, Seki R, Sakaki Y. Mechanism of chromosomal integration of transgenes in microinjected mouse eggs: sequence analysis of genome-transgene and transgene-transgene junctions at two loci. Gene X 1993; 128:197-202. [PMID: 8390388 DOI: 10.1016/0378-1119(93)90563-i] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Production of transgenic animals is a key technique in modern biology, but the process of chromosomal integration of transgenes in microinjected eggs is still not fully understood. To gain information on the mechanisms involved in this process, we have cloned two transgene loci and their corresponding pre-integration sites and compared the junction sequences with the parental nucleotide (nt) sequences. No extensive DNA rearrangements were detected at these loci: only simple deletions (caused by the integration of the transgene concatemers) were present in the host genome. Analysis of three transgene-transgene junctions within the concatemers showed that 'nibbling' of ends (up to 3 nt) had occurred at some ends prior to joining. At all four genome-transgene junctions, short homologies of 1 to 3 nt were found, and at least three of these junctions were associated with the consensus sequence for topoisomerase-I cleavage sites. Moreover, three of the four integration junctions occurred in the terminal regions of the injected sequence, at positions only a few nt away from the ends. These results suggest that linear, but not circular, concatemers were preferentially integrated at their ends utilizing short homologies to the host genome.
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Affiliation(s)
- T Hamada
- Research Laboratory for Genetic Information, Kyushu University Fukuoka, Japan
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27
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Bevan IS, Rapley R, Walker MR. Sequencing of PCR-amplified DNA. PCR METHODS AND APPLICATIONS 1992; 1:222-8. [PMID: 1477656 DOI: 10.1101/gr.1.4.222] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Alternatives for sequencing of PCR products essentially fall into one of two categories; generation of single-stranded DNA for sequencing or the direct sequencing of double-stranded product. Of the two alternatives, sequencing of double-stranded PCR products is likely to be of greatest immediate significance in terms of general applicability and rapidity. Double-stranded sequencing allows the use of the PCR product for other purposes either prior to or subsequent to generation of sequence data. The single-stranded sequencing methods generally require some prior decision regarding sequencing of the product. Assisted by automated workstation development, sequencing of single-stranded DNA PCR products generated either during thermal cycling or following affinity-capture strand separation may have significant future utility, particularly in genome mapping and routine clinical diagnosis. Despite template type and protocol differences, in all situations the purity and concentration of PCR-amplified DNA template used remains the most critical factor determining the efficiency and reliability of nucleotide sequencing methods.
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Affiliation(s)
- I S Bevan
- University Department of Clinical Biochemistry, Wolfson Research Laboratories, Queen Elizabeth Medical Centre, Edgbaston, Birmingham, UK
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