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Paul E Mead - One of the best experts on this subject based on the ideXlab platform.
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Remobilization of Sleeping Beauty transposons in the germline of Xenopus tropicalis
Mobile DNA, 2011Co-Authors: Donald Yergeau, Clair M Kelley, Emin Kuliyev, Haiqing Zhu, Amy K Sater, Dan E Wells, Michelle R. Johnson Hamlet, Paul E MeadAbstract: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.
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Remobilization of Tol2 transposons in Xenopus tropicalis
BMC Developmental Biology, 2010Co-Authors: Donald A Yergeau, Clair M Kelley, Emin Kuliyev, Haiqing Zhu, Amy K Sater, Dan E Wells, Paul E MeadAbstract:Background The Class II DNA transposons are mobile genetic elements that move DNA sequence from one position in the genome to another. We have previously demonstrated that the naturally occurring Tol2 element from Oryzias latipes efficiently integrates its corresponding non-autonomous transposable element into the genome of the diploid frog, Xenopus tropicalis. Tol2 transposons are stable in the frog genome and are transmitted to the offspring at the expected Mendelian frequency. Results To test whether Tol2 transposons integrated in the Xenopus tropicalis genome are substrates for remobilization, we injected in vitro transcribed Tol2 mRNA into one-cell embryos harbouring a single copy of a Tol2 transposon. Integration site analysis of injected embryos from two founder lines showed at least one somatic remobilization event per embryo. We also demonstrate that the remobilized transposons are transmitted through the germline and re-integration can result in the generation of novel GFP expression patterns in the developing tadpole. Although the parental line contained a single Tol2 transposon, the resulting remobilized tadpoles frequently inherit multiple copies of the transposon. This is likely to be due to the Tol2 transposase acting in discrete blastomeres of the developing injected embryo during the cell cycle after DNA synthesis but prior to mitosis. Conclusions In this study, we demonstrate that single copy Tol2 transposons integrated into the Xenopus tropicalis genome are effective substrates for excision and random re-integration and that the remobilized transposons are transmitted through the germline. This is an important step in the development of 'transposon hopping' strategies for insertional mutagenesis, gene trap and enhancer trap screens in this highly tractable developmental model organism.
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Remobilization of Tol2 transposons in Xenopus tropicalis
BMC developmental biology, 2010Co-Authors: Donald A Yergeau, Clair M Kelley, Emin Kuliyev, Haiqing Zhu, Amy K Sater, Dan E Wells, Paul E MeadAbstract:Background The Class II DNA transposons are mobile genetic elements that move DNA sequence from one position in the genome to another. We have previously demonstrated that the naturally occurring Tol2 element from Oryzias latipes efficiently integrates its corresponding non-autonomous transposable element into the genome of the diploid frog, Xenopus tropicalis. Tol2 transposons are stable in the frog genome and are transmitted to the offspring at the expected Mendelian frequency.
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Tol2 transposon-mediated transgenesis in Xenopus tropicalis.
Genesis (New York N.Y. : 2000), 2006Co-Authors: Michelle R. Johnson Hamlet, Emin Kuliyev, Donald Yergeau, Masatoshi Takeda, Masanori Taira, Koichi Kawakami, Paul E MeadAbstract:The diploid frog Xenopus tropicalis is becoming a powerful developmental genetic model system. Sequencing of the X. tropicalis genome is nearing completion and several labs are embarking on mutagenesis screens. We are interested in developing insertional mutagenesis strategies in X. tropicalis. Transposon-mediated insertional mutagenesis, once used exclusively in plants and invertebrate systems, is now more widely applicable to vertebrates. The first step in developing transposons as tools for mutagenesis is to demonstrate that these mobile elements function efficiently in the target organism. Here, we show that the Medaka fish transposon, Tol2, is able to stably integrate into the X. tropicalis genome and will serve as a powerful tool for insertional mutagenesis strategies in the frog. genesis 44:438–445, 2006 Published 2006 Wiley-Liss, Inc.
Dan E Wells - One of the best experts on this subject based on the ideXlab platform.
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Remobilization of Sleeping Beauty transposons in the germline of Xenopus tropicalis
Mobile DNA, 2011Co-Authors: Donald Yergeau, Clair M Kelley, Emin Kuliyev, Haiqing Zhu, Amy K Sater, Dan E Wells, Michelle R. Johnson Hamlet, Paul E MeadAbstract: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.
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A genetic map of Xenopus tropicalis
Developmental biology, 2011Co-Authors: Dan E Wells, Vladimir Krylov, Jaroslav Macha, Laura Gutierrez, Kerstin P. Blankenburg, Matthew Hitchens, Larry J. Bellot, Mary Spivey, Derek L. StempleAbstract: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 132 cM in length, and 4 smaller linkage groups between 7 and 40 cM. The total effective size of the map is 1658 cM, and the average intermarker distance for each linkage group ranged from 0.27 to 0.75 cM. 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 100,000 bp. The genetic map and SSLP marker database constitute an essential resource for genetic and genomic analyses in X. tropicalis.
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Remobilization of Tol2 transposons in Xenopus tropicalis
BMC Developmental Biology, 2010Co-Authors: Donald A Yergeau, Clair M Kelley, Emin Kuliyev, Haiqing Zhu, Amy K Sater, Dan E Wells, Paul E MeadAbstract:Background The Class II DNA transposons are mobile genetic elements that move DNA sequence from one position in the genome to another. We have previously demonstrated that the naturally occurring Tol2 element from Oryzias latipes efficiently integrates its corresponding non-autonomous transposable element into the genome of the diploid frog, Xenopus tropicalis. Tol2 transposons are stable in the frog genome and are transmitted to the offspring at the expected Mendelian frequency. Results To test whether Tol2 transposons integrated in the Xenopus tropicalis genome are substrates for remobilization, we injected in vitro transcribed Tol2 mRNA into one-cell embryos harbouring a single copy of a Tol2 transposon. Integration site analysis of injected embryos from two founder lines showed at least one somatic remobilization event per embryo. We also demonstrate that the remobilized transposons are transmitted through the germline and re-integration can result in the generation of novel GFP expression patterns in the developing tadpole. Although the parental line contained a single Tol2 transposon, the resulting remobilized tadpoles frequently inherit multiple copies of the transposon. This is likely to be due to the Tol2 transposase acting in discrete blastomeres of the developing injected embryo during the cell cycle after DNA synthesis but prior to mitosis. Conclusions In this study, we demonstrate that single copy Tol2 transposons integrated into the Xenopus tropicalis genome are effective substrates for excision and random re-integration and that the remobilized transposons are transmitted through the germline. This is an important step in the development of 'transposon hopping' strategies for insertional mutagenesis, gene trap and enhancer trap screens in this highly tractable developmental model organism.
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Remobilization of Tol2 transposons in Xenopus tropicalis
BMC developmental biology, 2010Co-Authors: Donald A Yergeau, Clair M Kelley, Emin Kuliyev, Haiqing Zhu, Amy K Sater, Dan E Wells, Paul E MeadAbstract:Background The Class II DNA transposons are mobile genetic elements that move DNA sequence from one position in the genome to another. We have previously demonstrated that the naturally occurring Tol2 element from Oryzias latipes efficiently integrates its corresponding non-autonomous transposable element into the genome of the diploid frog, Xenopus tropicalis. Tol2 transposons are stable in the frog genome and are transmitted to the offspring at the expected Mendelian frequency.
Thomas Naert - One of the best experts on this subject based on the ideXlab platform.
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CRISPR/Cas9-Mediated Knockout of Rb1 in Xenopus tropicalis.
Methods in molecular biology (Clifton N.J.), 2018Co-Authors: Thomas Naert, Kris VleminckxAbstract:At this time, no molecular targeted therapies exist for treatment of retinoblastoma. This can be, in part, attributed to the lack of animal models that allow for both rapid identification of novel therapeutic targets and hypothesis driven drug testing. Within this scope, we have recently reported the first genuine genetic nonmammalian retinoblastoma cancer model within the aquatic model organism Xenopus tropicalis (Naert et al., Sci Rep 6: 35263, 2016). Here we describe the methods to generate rb1 mosaic mutant Xenopus tropicalis by employing the CRISPR/Cas9 technology. In depth, we discuss short guide RNA (sgRNA) design parameters, generation, quality control, quantification, and delivery followed by several methods for assessing genome editing efficiencies. As such the reader should be capable, by minor changes to the methods described here, to (co-) target rb1 or any one or multiple gene(s) within the Xenopus tropicalis genome by multiplex CRISPR/Cas9 methodology.
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CRISPR/Cas9 mediated knockout of rb1 and rbl1 leads to rapid and penetrant retinoblastoma development in Xenopus tropicalis
Scientific reports, 2016Co-Authors: Thomas Naert, Tom Van Nieuwenhuysen, Robin Colpaert, Dionysia Dimitrakopoulou, Jannick Leoen, Jurgen Haustraete, Annekatrien Boel, Wouter Steyaert, Trees Lepez, Dieter DeforceAbstract:Retinoblastoma is a pediatric eye tumor in which bi-allelic inactivation of the Retinoblastoma 1 (RB1) gene is the initiating genetic lesion. Although recently curative rates of retinoblastoma have increased, there are at this time no molecular targeted therapies available. This is, in part, due to the lack of highly penetrant and rapid retinoblastoma animal models that facilitate rapid identification of targets that allow therapeutic intervention. Different mouse models are available, all based on genetic deactivation of both Rb1 and Retinoblastoma-like 1 (Rbl1), and each showing different kinetics of retinoblastoma development. Here, we show by CRISPR/Cas9 techniques that similar to the mouse, neither rb1 nor rbl1 single mosaic mutant Xenopus tropicalis develop tumors, whereas rb1/rbl1 double mosaic mutant tadpoles rapidly develop retinoblastoma. Moreover, occasionally presence of pinealoblastoma (trilateral retinoblastoma) was detected. We thus present the first CRISPR/Cas9 mediated cancer model in Xenopus tropicalis and the first genuine genetic non-mammalian retinoblastoma model. The rapid kinetics of our model paves the way for use as a pre-clinical model. Additionally, this retinoblastoma model provides unique possibilities for fast elucidation of novel drug targets by triple multiplex CRISPR/Cas9 gRNA injections (rb1 + rbl1 + modifier gene) in order to address the clinically unmet need of targeted retinoblastoma therapy.
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crispr cas9 mediated knockout of rb1 and rbl1 leads to rapid and penetrant retinoblastoma development in Xenopus tropicalis
Scientific Reports, 2016Co-Authors: Thomas Naert, Tom Van Nieuwenhuysen, Robin Colpaert, Dionysia Dimitrakopoulou, Jannick Leoen, Jurgen Haustraete, Annekatrien Boel, Wouter Steyaert, Trees Lepez, Dieter DeforceAbstract:Retinoblastoma is a pediatric eye tumor in which bi-allelic inactivation of the Retinoblastoma 1 (RB1) gene is the initiating genetic lesion. Although recently curative rates of retinoblastoma have increased, there are at this time no molecular targeted therapies available. This is, in part, due to the lack of highly penetrant and rapid retinoblastoma animal models that facilitate rapid identification of targets that allow therapeutic intervention. Different mouse models are available, all based on genetic deactivation of both Rb1 and Retinoblastoma-like 1 (Rbl1), and each showing different kinetics of retinoblastoma development. Here, we show by CRISPR/Cas9 techniques that similar to the mouse, neither rb1 nor rbl1 single mosaic mutant Xenopus tropicalis develop tumors, whereas rb1/rbl1 double mosaic mutant tadpoles rapidly develop retinoblastoma. Moreover, occasionally presence of pinealoblastoma (trilateral retinoblastoma) was detected. We thus present the first CRISPR/Cas9 mediated cancer model in Xenopus tropicalis and the first genuine genetic non-mammalian retinoblastoma model. The rapid kinetics of our model paves the way for use as a pre-clinical model. Additionally, this retinoblastoma model provides unique possibilities for fast elucidation of novel drug targets by triple multiplex CRISPR/Cas9 gRNA injections (rb1 + rbl1 + modifier gene) in order to address the clinically unmet need of targeted retinoblastoma therapy.
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TALEN-mediated apc mutation in Xenopus tropicalis phenocopies familial adenomatous polyposis.
Oncoscience, 2015Co-Authors: Tom Van Nieuwenhuysen, Thomas Naert, Hong Thi Tran, Griet Van Imschoot, Sarah Geurs, Ellen Sanders, David Creytens, Frans Van Roy, Kris VleminckxAbstract:Truncating mutations in the tumor suppressor gene adenomatous polyposis coli (APC) are the initiating step in the vast majority of sporadic colorectal cancers, and they underlie familial adenomatous polyposis (FAP) syndromes. Modeling of APC- driven tumor formation in the mouse has contributed substantially to our mechanistic understanding of the associated disease, but additional models are needed to explore therapeutic opportunities and overcome current limitations of mouse models. We report on a novel and penetrant genetic cancer model in Xenopus tropicalis, an aquatic tetrapod vertebrate with external development, diploid genome and short life cycle. Tadpoles and froglets derived from embryos injected with TAL effector nucleases targeting the apc gene rapidly developed intestinal hyperplasia and other neoplasms observed in FAP patients, including desmoid tumors and medulloblastomas. Bi-allelic apc mutations causing frame shifts were detected in the tumors, which displayed activation of the Wnt/β-catenin pathway and showed increased cellular proliferation. We further demonstrate that simultaneous double bi-allelic mutation of apc and a non-relevant gene is possible in the neoplasias, opening the door for identification and characterization of effector or modifier genes in tumors expressing truncated apc. Our results demonstrate the power of modeling human cancer in Xenopus tropicalis using mosaic TALEN-mediated bi-allelic gene disruption.
Robert M Grainger - One of the best experts on this subject based on the ideXlab platform.
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Special Considerations for Making Explants and Transplants with Xenopus tropicalis.
Cold Spring Harbor protocols, 2019Co-Authors: Marilyn Fisher, Robert M GraingerAbstract:Although Xenopus laevis is an important model organism for embryological experimentation, the smaller, more genetically tractable, and faster developing Xenopus tropicalis provides advantages for using genetic approaches to understand developmental mechanisms. Explant cultures and transplants of X. tropicalis embryonic tissues present unique opportunities to examine embryonic tissue determination in a simplified setting. Here we demonstrate preparation of explants and transplants of preplacodal head ectoderm in order to illustrate these approaches; however, these methods apply broadly to tissues throughout the embryo. We focus on technical adjustments to accommodate the differences in size, tissue character, and rate of development between X. laevis and X. tropicalis With only modest modifications, X. tropicalis embryos are quite amenable to the same kinds of experimental manipulations as X. laevis.
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Cas9-based genome editing in Xenopus tropicalis.
Methods in enzymology, 2014Co-Authors: Takuya Nakayama, Ira L. Blitz, Margaret B. Fish, Akinleye O. Odeleye, Sumanth Manohar, Ken W.y. Cho, Robert M GraingerAbstract:Xenopus tropicalis has been developed as a model organism for developmental biology, providing a system offering both modern genetics and classical embryology. Recently, the Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated (CRISPR/Cas) system for genome modification has provided an additional tool for Xenopus researchers to achieve simple and efficient targeted mutagenesis. Here, we provide insights into experimental design and procedures permitting successful application of this technique to Xenopus researchers, and offer a general strategy for performing loss-of-function assays in F0 and subsequently F1 embryos.
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simple and efficient crispr cas9 mediated targeted mutagenesis in Xenopus tropicalis
Genesis, 2013Co-Authors: Takuya Nakayama, Margaret B. Fish, Marilyn Fisher, Gerald H. Thomsen, Jamina Oomenhajagos, Robert M GraingerAbstract:We have assessed the efficacy of the recently developed CRISPR/Cas (clustered regularly interspaced short palindromic repeats/CRISPR-associated) system for genome modification in the amphibian Xenopus tropicalis. As a model experiment, targeted mutations of the tyrosinase gene were verified, showing the expected albinism phenotype in injected embryos. We further tested this technology by interrupting the six3 gene, which is required for proper eye and brain formation. Expected eye and brain phenotypes were observed when inducing mutations in the six3 coding regions, as well as when deleting the gene promoter by dual targeting. We describe here a standardized protocol for genome editing using this system. This simple and fast method to edit the genome provides a powerful new reverse genetics tool for Xenopus researchers.
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simple and efficient crispr cas9 mediated targeted mutagenesis in Xenopus tropicalis
Genesis, 2013Co-Authors: Takuya Nakayama, Margaret B. Fish, Marilyn Fisher, Gerald H. Thomsen, Jamina Oomenhajagos, Robert M GraingerAbstract:We have assessed the efficacy of the recently developed CRISPR/Cas (clustered regularly interspaced short palindromic repeats/CRISPR-associated) system for genome modification in the amphibian Xenopus tropicalis. As a model experiment, targeted mutations of the tyrosinase gene were verified, showing the expected albinism phenotype in injected embryos. We further tested this technology by interrupting the six3 gene, which is required for proper eye and brain formation. Expected eye and brain phenotypes were observed when inducing mutations in the six3 coding regions, as well as when deleting the gene promoter by dual targeting. We describe here a standardized protocol for genome editing using this system. This simple and fast method to edit the genome provides a powerful new reverse genetics tool for Xenopus researchers. genesis 51:835–843. © 2013 Wiley Periodicals, Inc.
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Simple and efficient CRISPR/Cas9-mediated targeted mutagenesis in Xenopus tropicalis.
Genesis (New York N.Y. : 2000), 2013Co-Authors: Takuya Nakayama, Margaret B. Fish, Marilyn Fisher, Jamina Oomen-hajagos, Gerald H. Thomsen, Robert M GraingerAbstract:We have assessed the efficacy of the recently developed CRISPR/Cas (clustered regularly interspaced short palindromic repeats/CRISPR-associated) system for genome modification in the amphibian Xenopus tropicalis. As a model experiment, targeted mutations of the tyrosinase gene were verified, showing the expected albinism phenotype in injected embryos. We further tested this technology by interrupting the six3 gene, which is required for proper eye and brain formation. Expected eye and brain phenotypes were observed when inducing mutations in the six3 coding regions, as well as when deleting the gene promoter by dual targeting. We describe here a standardized protocol for genome editing using this system. This simple and fast method to edit the genome provides a powerful new reverse genetics tool for Xenopus researchers.
Dieter Deforce - One of the best experts on this subject based on the ideXlab platform.
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CRISPR/Cas9 mediated knockout of rb1 and rbl1 leads to rapid and penetrant retinoblastoma development in Xenopus tropicalis
Scientific reports, 2016Co-Authors: Thomas Naert, Tom Van Nieuwenhuysen, Robin Colpaert, Dionysia Dimitrakopoulou, Jannick Leoen, Jurgen Haustraete, Annekatrien Boel, Wouter Steyaert, Trees Lepez, Dieter DeforceAbstract:Retinoblastoma is a pediatric eye tumor in which bi-allelic inactivation of the Retinoblastoma 1 (RB1) gene is the initiating genetic lesion. Although recently curative rates of retinoblastoma have increased, there are at this time no molecular targeted therapies available. This is, in part, due to the lack of highly penetrant and rapid retinoblastoma animal models that facilitate rapid identification of targets that allow therapeutic intervention. Different mouse models are available, all based on genetic deactivation of both Rb1 and Retinoblastoma-like 1 (Rbl1), and each showing different kinetics of retinoblastoma development. Here, we show by CRISPR/Cas9 techniques that similar to the mouse, neither rb1 nor rbl1 single mosaic mutant Xenopus tropicalis develop tumors, whereas rb1/rbl1 double mosaic mutant tadpoles rapidly develop retinoblastoma. Moreover, occasionally presence of pinealoblastoma (trilateral retinoblastoma) was detected. We thus present the first CRISPR/Cas9 mediated cancer model in Xenopus tropicalis and the first genuine genetic non-mammalian retinoblastoma model. The rapid kinetics of our model paves the way for use as a pre-clinical model. Additionally, this retinoblastoma model provides unique possibilities for fast elucidation of novel drug targets by triple multiplex CRISPR/Cas9 gRNA injections (rb1 + rbl1 + modifier gene) in order to address the clinically unmet need of targeted retinoblastoma therapy.
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crispr cas9 mediated knockout of rb1 and rbl1 leads to rapid and penetrant retinoblastoma development in Xenopus tropicalis
Scientific Reports, 2016Co-Authors: Thomas Naert, Tom Van Nieuwenhuysen, Robin Colpaert, Dionysia Dimitrakopoulou, Jannick Leoen, Jurgen Haustraete, Annekatrien Boel, Wouter Steyaert, Trees Lepez, Dieter DeforceAbstract:Retinoblastoma is a pediatric eye tumor in which bi-allelic inactivation of the Retinoblastoma 1 (RB1) gene is the initiating genetic lesion. Although recently curative rates of retinoblastoma have increased, there are at this time no molecular targeted therapies available. This is, in part, due to the lack of highly penetrant and rapid retinoblastoma animal models that facilitate rapid identification of targets that allow therapeutic intervention. Different mouse models are available, all based on genetic deactivation of both Rb1 and Retinoblastoma-like 1 (Rbl1), and each showing different kinetics of retinoblastoma development. Here, we show by CRISPR/Cas9 techniques that similar to the mouse, neither rb1 nor rbl1 single mosaic mutant Xenopus tropicalis develop tumors, whereas rb1/rbl1 double mosaic mutant tadpoles rapidly develop retinoblastoma. Moreover, occasionally presence of pinealoblastoma (trilateral retinoblastoma) was detected. We thus present the first CRISPR/Cas9 mediated cancer model in Xenopus tropicalis and the first genuine genetic non-mammalian retinoblastoma model. The rapid kinetics of our model paves the way for use as a pre-clinical model. Additionally, this retinoblastoma model provides unique possibilities for fast elucidation of novel drug targets by triple multiplex CRISPR/Cas9 gRNA injections (rb1 + rbl1 + modifier gene) in order to address the clinically unmet need of targeted retinoblastoma therapy.
