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Abstract
hAT transposons are ancient in their origin and they are widespread across eukaryote kingdoms. They can be present in large numbers in many genomes. However, only a few active forms of these elements have so far been discovered indicating that, like all transposable elements, there is selective pressure to inactivate them. Nonetheless, there have been sufficient numbers of active hAT elements and their transposases characterized that permit an analysis of their structure and function. This review analyzes these and provides a comparison with the several domesticated hAT genes discovered in eukaryote genomes. Active hAT transposons have also been developed as genetic tools and understanding how these may be optimally utilized in new hosts will depend, in part, on understanding the basis of their function in genomes.
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Lane MA, Kimber M, Khokha MK. Breeding based remobilization of Tol2 transposon in Xenopus tropicalis. PLoS One 2013; 8:e76807. [PMID: 24116167 PMCID: PMC3792888 DOI: 10.1371/journal.pone.0076807] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Accepted: 08/30/2013] [Indexed: 01/17/2023] Open
Abstract
Xenopus is a powerful model for studying a diverse array of biological processes. However, despite multiple methods for transgenesis, relatively few transgenic reporter lines are available and commonly used. Previous work has demonstrated that transposon based strategies are effective for generating transgenic lines in both invertebrate and vertebrate systems. Here we show that the Tol2 transposon can be remobilized in the genome of X. tropicalis and passed through the germline via a simple breeding strategy of crossing transposase expressing and transposon lines. This remobilization system provides another tool to exploit transgenesis and opens new opportunities for gene trap and enhancer trap strategies.
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Affiliation(s)
- Maura A. Lane
- Program in Vertebrate Developmental Biology, Department of Pediatrics and Genetics, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Megan Kimber
- Program in Vertebrate Developmental Biology, Department of Pediatrics and Genetics, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Mustafa K. Khokha
- Program in Vertebrate Developmental Biology, Department of Pediatrics and Genetics, Yale University School of Medicine, New Haven, Connecticut, United States of America
- * E-mail:
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Takagi C, Sakamaki K, Morita H, Hara Y, Suzuki M, Kinoshita N, Ueno N. Transgenic Xenopus laevis for live imaging in cell and developmental biology. Dev Growth Differ 2013; 55:422-33. [PMID: 23480392 DOI: 10.1111/dgd.12042] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Revised: 01/08/2013] [Accepted: 01/08/2013] [Indexed: 01/28/2023]
Abstract
The stable transgenesis of genes encoding functional or spatially localized proteins, fused to fluorescent proteins such as green fluorescent protein (GFP) or red fluorescent protein (RFP), is an extremely important research tool in cell and developmental biology. Transgenic organisms constructed with fluorescent labels for cell membranes, subcellular organelles, and functional proteins have been used to investigate cell cycles, lineages, shapes, and polarity, in live animals and in cells or tissues derived from these animals. Genes of interest have been integrated and maintained in generations of transgenic animals, which have become a valuable resource for the cell and developmental biology communities. Although the use of Xenopus laevis as a transgenic model organism has been hampered by its relatively long reproduction time (compared to Drosophila melanogaster and Caenorhabditis elegans), its large embryonic cells and the ease of manipulation in early embryos have made it a historically valuable preparation that continues to have tremendous research potential. Here, we report on the Xenopus laevis transgenic lines our lab has generated and discuss their potential use in biological imaging.
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Affiliation(s)
- Chiyo Takagi
- National Institute for Basic Biology, 38 Nishigonaka, Myodaiji, Okazaki, 444-8585, Japan
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Song G, Li Q, Long Y, Hackett PB, Cui Z. Effective Expression-Independent Gene Trapping and Mutagenesis Mediated by Sleeping Beauty Transposon. J Genet Genomics 2012; 39:503-20. [DOI: 10.1016/j.jgg.2012.05.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Revised: 05/21/2012] [Accepted: 05/28/2012] [Indexed: 01/12/2023]
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Effective gene trapping mediated by Sleeping Beauty transposon. PLoS One 2012; 7:e44123. [PMID: 22952894 PMCID: PMC3432063 DOI: 10.1371/journal.pone.0044123] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2012] [Accepted: 07/30/2012] [Indexed: 01/14/2023] Open
Abstract
Gene trapping is a high-throughput approach to elucidate gene functions by disrupting and recapitulating expression of genes in a target genome. A number of transposon-based gene-trapping systems are developed for mutagenesis in cells and model organisms, but there is still much room for the improvement of their efficiency in gene disruption and mutation. Herein, a gene-trapping system mediated by Sleeping Beauty (SB) transposon was developed by inclusion of three functional cassettes. The mutation cassette can abrogate the splice of trapped genes and terminate their translation. Once an endogenous gene is captured, the finding cassette independently drives the translation of reporter gene in HeLa cells and zebrafish embryos. The efficiency cassette controls the remobilization of integrated traps through inducible expression of SB gene. Analysis of transposon-genome junctions indicate that most of trap cassettes are integrated into an intron without an obvious 3′ bias. The transcription of trapped genes was abrogated by alternative splicing of the mutation cassette. In addition, integrated transposons can be induced to excise from their original insertion sites. Furthermore, the Cre/LoxP system was introduced to delete the efficiency cassette for stabilization of gene interruption and bio-safety. Thus, this gene-trap vector is an alternative and effective tool for the capture and disruption of endogenous genes in vitro and in vivo.
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Abu-Daya A, Khokha MK, Zimmerman LB. The hitchhiker's guide to Xenopus genetics. Genesis 2012; 50:164-75. [PMID: 22344745 DOI: 10.1002/dvg.22007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2011] [Revised: 12/19/2011] [Accepted: 12/23/2011] [Indexed: 01/12/2023]
Abstract
A decade after the human genome sequence, most vertebrate gene functions remain poorly understood, limiting benefits to human health from rapidly advancing genomic technologies. Systematic in vivo functional analysis is ideally suited to the experimentally accessible Xenopus embryo, which combines embryological accessibility with a broad range of transgenic, biochemical, and gain-of-function assays. The diploid X. tropicalis adds loss-of-function genetics and enhanced genomics to this repertoire. In the last decade, diverse phenotypes have been recovered from genetic screens, mutations have been cloned, and reverse genetics in the form of TILLING and targeted gene editing have been established. Simple haploid genetics and gynogenesis and the very large number of embryos produced streamline screening and mapping. Improved genomic resources and the revolution in high-throughput sequencing are transforming mutation cloning and reverse genetic approaches. The combination of loss-of-function mutant backgrounds with the diverse array of conventional Xenopus assays offers a uniquely flexible platform for analysis of gene function in vertebrate development.
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Affiliation(s)
- Anita Abu-Daya
- Division of Developmental Biology, MRC-National Institute for Medical Research, Mill Hill, London, United Kingdom
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Abstract
The pipid frog Xenopus tropicalis has emerged as a powerful new model system for combining genetic and genomic analysis of tetrapod development with robust embryological, molecular, and biochemical assays. Its early development closely resembles that of its well-understood relative X. laevis, from which techniques and reagents can be readily transferred. In contrast to the tetraploid X. laevis, X. tropicalis has a compact diploid genome with strong synteny to those of amniotes. Recently, advances in high-throughput sequencing together with solution-hybridization whole-exome enrichment technology offer powerful strategies for cloning novel mutations as well as reverse genetic identification of sequence lesions in specific genes of interest. Further advantages include the wide range of functional and molecular assays available, the large number of embryos/meioses produced, and the ease of haploid genetics and gynogenesis. The addition of these genetic tools to X. tropicalis provides a uniquely flexible platform for analysis of gene function in vertebrate development.
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Affiliation(s)
- Timothy J. Geach
- National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA United Kingdom
| | | | - Lyle B. Zimmerman
- National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA United Kingdom
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Yergeau DA, Kelley CM, Zhu H, Kuliyev E, Mead PE. Forward genetic screens in Xenopus using transposon-mediated insertional mutagenesis. Methods Mol Biol 2012; 917:111-127. [PMID: 22956084 DOI: 10.1007/978-1-61779-992-1_6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The class II DNA "cut-and-paste" transposons have been used to efficiently modify the Xenopus genome for transgenesis applications. Once integrated, the transposon is an effective substrate for excision and re-integration (remobilization) elsewhere in the genome by simply supplying the transposase enzyme in trans. We have used two methods to remobilize transposons resident in the frog genome: micro-injection of transposase mRNA at the one-cell stage and expression of the enzyme in the germline from a transgene. Double-transgenic frogs (hoppers) that harbor transgenes for both the substrate transposon and the transposase enzyme are outcrossed to wild-type animals and the progeny are scored for changes in reporter gene expression. Although both methods work effectively to remobilize transposons, the breeding-mediated strategy eliminates the time-consuming micro-injection step; novel integration events are produced by simply outcrossing the hopper frogs. As each outcross of Xenopus tropicalis typically produces 2,000, or more, progeny, this method can be used to perform large-scale insertional mutagenesis screens in this highly tractable developmental model system.
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Affiliation(s)
- Donald A Yergeau
- Department of Pathology, St. Jude Children's Research Hospital, Memphis, TN, USA
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Kelley CM, Yergeau DA, Zhu H, Kuliyev E, Mead PE. Xenopus transgenics: methods using transposons. Methods Mol Biol 2012; 917:231-43. [PMID: 22956092 DOI: 10.1007/978-1-61779-992-1_14] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
Abstract
The generation of transgenic animals is an essential tool for many genetic strategies. DNA "cut-and-paste" transposon systems can be used to efficiently modify the Xenopus genome. The DNA transposon substrate, harbored on a circularized plasmid, is co-injected into fertilized Xenopus embryos at the one-cell stage together with mRNA encoding the cognate transposase enzyme. The cellular machinery rapidly translates the exogenous mRNA to produce active transposase enzyme that catalyzes excision of the transposon substrate from the plasmid and stable integration into the genomic DNA.
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Affiliation(s)
- Clair M Kelley
- Department of Pathology, St. Jude Children's Research Hospital, Memphis, TN, USA
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Remobilization of Sleeping Beauty transposons in the germline of Xenopus tropicalis. Mob DNA 2011; 2:15. [PMID: 22115366 PMCID: PMC3271037 DOI: 10.1186/1759-8753-2-15] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Accepted: 11/24/2011] [Indexed: 12/03/2022] Open
Abstract
Background The Sleeping Beauty (SB) transposon system has been used for germline transgenesis of the diploid frog, Xenopus tropicalis. Injecting one-cell embryos with plasmid DNA harboring an SB transposon substrate together with mRNA encoding the SB transposase enzyme resulted in non-canonical integration of small-order concatemers of the transposon. Here, we demonstrate that SB transposons stably integrated into the frog genome are effective substrates for remobilization. Results Transgenic frogs that express the SB10 transposase were bred with SB transposon-harboring animals to yield double-transgenic 'hopper' frogs. Remobilization events were observed in the progeny of the hopper frogs and were verified by Southern blot analysis and cloning of the novel integrations sites. Unlike the co-injection method used to generate founder lines, transgenic remobilization resulted in canonical transposition of the SB transposons. The remobilized SB transposons frequently integrated near the site of the donor locus; approximately 80% re-integrated with 3 Mb of the donor locus, a phenomenon known as 'local hopping'. Conclusions In this study, we demonstrate that SB transposons integrated into the X. tropicalis genome are effective substrates for excision and re-integration, and that the remobilized transposons are transmitted through the germline. This is an important step in the development of large-scale transposon-mediated gene- and enhancer-trap strategies in this highly tractable developmental model system.
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Wells DE, Gutierrez L, Xu Z, Krylov V, Macha J, Blankenburg KP, Hitchens M, Bellot LJ, Spivey M, Stemple DL, Kowis A, Ye Y, Pasternak S, Owen J, Tran T, Slavikova R, Tumova L, Tlapakova T, Seifertova E, Scherer SE, Sater AK. A genetic map of Xenopus tropicalis. Dev Biol 2011; 354:1-8. [PMID: 21458440 PMCID: PMC3098391 DOI: 10.1016/j.ydbio.2011.03.022] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2010] [Revised: 03/05/2011] [Accepted: 03/11/2011] [Indexed: 01/22/2023]
Abstract
We present a genetic map for Xenopus tropicalis, consisting of 2886 Simple Sequence Length Polymorphism (SSLP) markers. Using a bioinformatics-based strategy, we identified unique SSLPs within the X. tropicalis genome. Scaffolds from X. tropicalis genome assembly 2.0 (JGI) were scanned for Simple Sequence Repeats (SSRs); unique SSRs were then tested for amplification and polymorphisms using DNA from inbred Nigerian and Ivory Coast individuals. Thus identified, the SSLPs were genotyped against a mapping cross panel of DNA samples from 190 F2 individuals. Nearly 4000 SSLPs were genotyped, yielding a 2886-marker genetic map consisting of 10 major linkage groups between 73 and 132cM in length, and 4 smaller linkage groups between 7 and 40cM. The total effective size of the map is 1658cM, and the average intermarker distance for each linkage group ranged from 0.27 to 0.75cM. Fluorescence In Situ Hybridization (FISH) was carried out using probes for genes located on mapped scaffolds to assign linkage groups to chromosomes. Comparisons of this map with the X. tropicalis genome Assembly 4.1 (JGI) indicate that the map provides representation of a minimum of 66% of the X. tropicalis genome, incorporating 758 of the approximately 1300 scaffolds over 100,000bp. The genetic map and SSLP marker database constitute an essential resource for genetic and genomic analyses in X. tropicalis.
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Affiliation(s)
- Dan E Wells
- Department of Biology and Biochemistry, University of Houston, 4800 Calhoun Rd., Houston TX 77204-5001, USA
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Yergeau DA, Kelley CM, Zhu H, Kuliyev E, Mead PE. Transposon transgenesis in Xenopus. Methods 2010; 51:92-100. [PMID: 20211730 DOI: 10.1016/j.ymeth.2010.03.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2010] [Revised: 02/26/2010] [Accepted: 03/02/2010] [Indexed: 11/16/2022] Open
Abstract
Transposon-mediated integration strategies in Xenopus offer simple and robust methods for the generation of germline transgenic animals. Co-injection of fertilized one-cell embryos with plasmid DNA harboring a transposon transgene and synthetic mRNA encoding the cognate transposase enzyme results in mosaic integration of the transposon at early cleavage stages that are frequently passed through the germline in the adult animal. Micro-injection of fertilized embryos is a routine procedure used by many laboratories that use Xenopus as a developmental model and, as such, the transposon transgenesis method can be performed without additional equipment or specialized methodologies. The methods for injecting Xenopus embryos are well documented in the literature so here we provide a step-by-step guide to other aspects of transposon transgenesis, including screening mosaic founders for germline transmission of the transgene and general husbandry considerations related to management of populations of transgenic frogs.
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Affiliation(s)
- Donald A Yergeau
- Department of Pathology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
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