Precise modifications of complex genomes at the single nucleotide level have been one of the big goals for scientists working in basic and applied genetics,including biotechnology,drug development,gene therapy and syn...Precise modifications of complex genomes at the single nucleotide level have been one of the big goals for scientists working in basic and applied genetics,including biotechnology,drug development,gene therapy and synthetic biology.However,the relevant techniques for making these manipulations in model organisms and human cells have been lagging behind the rapid high throughput studies in the post-genomic era with a bottleneck of low efficiency,time consuming and laborious manipulation,and off-targeting problems.Recent discoveries of TALEs（transcription activator-like effectors） coding system and CRISPR（clusters of regularly interspaced short palindromic repeats） immune system in bacteria have enabled the development of customized TALENs（transcription activator-like effector nucleases） and CRISPR/Cas9 to rapidly edit genomic DNA in a variety of cell types,including human cells,and different model organisms at a very high efficiency and specificity.In this review,we first briefly summarize the development and applications of TALENs and CRISPR/Cas9-mediated genome editing technologies;compare the advantages and constraints of each method;particularly,discuss the expected applications of both techniques in the field of site-specific genome modification and stem cell based gene therapy;finally, propose the future directions and perspectives for readers to make the choices.展开更多
Technology development has always been one of the forces driving breakthroughs in biomedical research. Since the time of Thomas Morgan, Drosophilists have, step by step, developed powerful genetic tools for manipulati...Technology development has always been one of the forces driving breakthroughs in biomedical research. Since the time of Thomas Morgan, Drosophilists have, step by step, developed powerful genetic tools for manipulating and functionally dissecting the Drosophila genome, but room for improving these technologies and developing new techniques is still large, especially today as biologists start to study systematically the functional genomics of different model organisms, including humans, in a high-throughput manner. Here, we report, for the first time in Drosophila, a rapid, easy, and highly specific method for modifying the Drosophila genome at a very high efficiency by means of an improved transcription activator-like effector nuclease （TALEN） strategy. We took advantage of the very recently developed ＂unit assembly＂ strategy to assemble two pairs of specific TALENs designed to modify the yellow gene （on the sex chromosome） and a novel autosomal gene. The mRNAs of TALENs were subsequently injected into Drosophila embryos. From 31.2% of the injected Fo fertile flies, we detected inheritable modification involving the yellow gene. The entire process from construction of specific TALENs to detection of inheritable modifications can be accomplished within one month. The potential applications of this TALEN-mediated genome modification method in Drosophila are discussed.展开更多
Gene editing in model organisms has provided critical insights into brain development and diseases. Here, we report the generation of a cynomolgus monkey （Macaca fascicularis） carrying MECP2 mutations using transcri...Gene editing in model organisms has provided critical insights into brain development and diseases. Here, we report the generation of a cynomolgus monkey （Macaca fascicularis） carrying MECP2 mutations using transcription activator-like effector nucleases （TALENs）-mediated gene targeting. After injecting TALENs mRNA into monkey zygotes achieved by in vitro fertilization and embryo transplantation into surrogate monkeys, we obtained one male newborn monkey with an MECP2 deletion caused by frame- shifting mutation in various tissues. The monkey carrying the MECP2 mutation failed to survive after birth, due to either the toxicity of TALENs or the critical requirement of MECP2 for neural development. The level of MeCP2 protein was essentially depleted in the monkey＇s brain. This study demonstrates the feasibility of introducing genetic mutations in non-human primates by site-specific gene-editing methods.展开更多
Over the last decades,much endeavor has been made to advance genome editing technology due to its promising role in both basic and synthetic biology.The breakthrough has been made in recent years with the advent of se...Over the last decades,much endeavor has been made to advance genome editing technology due to its promising role in both basic and synthetic biology.The breakthrough has been made in recent years with the advent of sequence-specific endonucleases,especially zinc finger nucleases（ZFNs）,transcription activator-like effector nucleases（TALENs） and clustered regularly interspaced short palindromic repeats（CRISPRs） guided nucleases（e.g.,Cas9）.In higher eukaryotic organisms,site-directed mutagenesis usually can be achieved through non-homologous end-joining（NHEJ） repair to the DNA double-strand breaks（DSBs） caused by the exogenously applied nucleases.However,site-specific gene replacement or genuine genome editing through homologous recombination（HR） repair to DSBs remains a challenge.As a proof of concept gene replacement through TALEN-based HR in rice（Oryza sativa）,we successfully produced double point mutations in rice acetolactate synthase gene（OsALS） and generated herbicide resistant rice lines by using TALENs and donor DNA carrying the desired mutations.After ballistic delivery into rice calli of TALEN construct and donor DNA,nine HR events with different genotypes of OsALS were obtained in T_0 generation at the efficiency of 1.4%—6.3%from three experiments.The HRmediated gene edits were heritable to the progeny of T_1 generation.The edited T_1 plants were as morphologically normal as the control plants while displayed strong herbicide resistance.The results demonstrate the feasibility of TALEN-mediated genome editing in rice and provide useful information for further genome editing by other nuclease-based genome editing platforms.展开更多
Breakthroughs in the generation of programmable sequence-specific nucleases (SSNs), such as zinc finger nucleases (ZFNs),TAL effector nucleases (TALENs) and the RNA-directed nuclease CRISPR-associated protein 9 (Cas9)...Breakthroughs in the generation of programmable sequence-specific nucleases (SSNs), such as zinc finger nucleases (ZFNs),TAL effector nucleases (TALENs) and the RNA-directed nuclease CRISPR-associated protein 9 (Cas9), have greatly increased the ease of plant genome engineering (Voytas, 2013; Malzahn et al.,2017). Programmable SSNs introduce a DNA double-strand break展开更多
The transcription activator-like effector nuclease （TALEN） technique combined with the somatic cel nuclear transfer （SCNT） method has been successfuly applied for creating geneticaly modiifed pigs. However, method...The transcription activator-like effector nuclease （TALEN） technique combined with the somatic cel nuclear transfer （SCNT） method has been successfuly applied for creating geneticaly modiifed pigs. However, methods for isolating cels with bialelic indels requires further improvement because of the relatively low enrichment efifciency of mutated somatic cels. Moreover, little is known regarding the off-target effects of the TALEN system and the heredity of TALEN-modiifed pigs. In this study, an efifcient method to increase the enrichment efifciency of TALEN-mediated bialelic knockout （KO） cels was established, and corresponding geneticaly modiifed pigs with the expected genotype were generated whose off-target effect, fertility and heredity characteristics were aslo evaluated. Two TALEN pairs were constructed to target the porcine α-1,3-galactosyltransferase （GGTA1） gene locus. TALEN mRNA was transfected into the ear ifbroblasts folowed by the enrichment of α-Gal nul cels of minipigs using isolectin B4 （IB4） lectin and magnetic beads. A total of 115 cel colonies were formed and validated to beGGTA1 KO cels by sequencing and 10 bialelic KO cel colonies were used as nuclear donors for SCNT. ThirtyGGTA1 bialelic KO piglets were successfuly delivered and grew normaly. Seventeen potential off-target sites were investigated, and no off-target events were detected in the live piglets. To determine the fertility and heredity characteristics of TALEN-modiifed pigs, 10 mature founders were mated with each other and the mutations were determined to be transmitted to the F1 piglets. We established a robust and safe technology for developing geneticaly modiifed pig lines with expected genotypes for agricultural breeding and biomedical application.展开更多
Mitochondrial diseases are maternally inherited hetero- geneous disorders that are primarily caused by mitochondrial DNA （mtDNA） mutations. Depending on the ratio of mutant to wild-type mtDNA, known as heteroplasmy,...Mitochondrial diseases are maternally inherited hetero- geneous disorders that are primarily caused by mitochondrial DNA （mtDNA） mutations. Depending on the ratio of mutant to wild-type mtDNA, known as heteroplasmy, mitochondrial defects can result in a wide spectrum of clinical manifestations. Mitochondria-targeted endonucleases provide an alternative avenue for treating mitochondrial disorders via targeted destruc- tion of the mutant mtDNA and induction of heteroplasmic shifting. Here, we generated mitochondrial disease patient-specific induced pluripotent stem cells （MiPSCs） that harbored a high proportion of m.3243A〉G mtDNA mutations and caused mitochondrial encephalomyopathy and stroke-like episodes （MELAS）. We engineered mitochondrial-targeted transcription activator-like effector nucleases （mitoTALENs） and successfully eliminated the m.3243A〉G mutation in MiPSCs. Off-target mutagenesis was not detected in the targeted MiPSC clones. Utilizing a dual fluorescence iPSC reporter cell line expressing a 3243G mutant mtDNA sequence in the nuclear genome, mitoTALENs displayed a significantly limited ability to target the nuclear genome compared with nuclear-localized TALENs. Moreover, genetically rescued MiPSCs displayed normal mitochondrial respiration and energy production. Moreover, neuronal progenitor cells differentiated from the rescued MiPSCs also demonstrated normal metabolic profiles. Further- more, we successfully achieved reduction in the human m.3243A〉G mtDNA mutation in porcine oocytes via injection of mitoTALEN mRNA. Our study shows the great potential for using mitoTALENs for specific targeting of mutant mtDNA both in iPSCs and mammalian oocytes, which not only provides a new avenue for studying mitochondrial biology and disease but also suggests a potential therapeutic approach for the treatment of mitochondrial disease, as well as the prevention of germline transmission of mutant mtDNA.展开更多
Pigs are an important resource in agriculture and serve as a model for human diseases. Due to their physiological and anatomical similarities with humans, pigs can recapitulate symptoms of human diseases, making them ...Pigs are an important resource in agriculture and serve as a model for human diseases. Due to their physiological and anatomical similarities with humans, pigs can recapitulate symptoms of human diseases, making them a useful model in biomedicine. However, in the past pig models have not been widely used partially because of the difficulty in genetic modification. The lack of true embryonic stem cells in pigs forced researchers to utilize genetic modification in somatic cells and somatic cell nuclear transfer(SCNT) to generate genetically engineered(GE) pigs carrying site-specific modifications. Although possible, this approach is extremely inefficient and GE pigs born through this method often presented developmental defects associated with the cloning process. Advancement in the gene-editing systems such as Zinc-Finger Nucleases(ZFNs), Transcription activator-like effector nucleases(TALENs), and the Clustered regularly interspaced short palindromic repeat(CRISPR)/CRISPR-associated 9(Cas9) system have dramatically increased the efficiency of producing GE pigs. These gene-editing systems, specifically engineered endonucleases, are based on inducing double-stranded breaks(DSBs) at a specific location, and then site-specific modifications can be introduced through one of the two DNA repair pathways: non-homologous end joining(NHEJ) or homology direct repair(HDR).Random insertions or deletions(indels) can be introduced through NHEJ and specific nucleotide sequences can be introduced through HDR, if donor DNA is provided. Use of these engineered endonucleases provides a higher success in genetic modifications, multiallelic modification of the genome, and an opportunity to introduce site-specific modifications during embryogenesis, thus bypassing the need of SCNT in GE pig production. This review will provide a historical prospective of GE pig production and examples of how the gene-editing system, led by engineered endonucleases, have improved GE pig production. We wil also present some of our current progress relate展开更多
Zebrafish（Danio rerio） is a well-established vertebrate animal model.A comprehensive collection of reverse genetics tools has been developed for studying gene function in this useful organism.Morpholino is the most ...Zebrafish（Danio rerio） is a well-established vertebrate animal model.A comprehensive collection of reverse genetics tools has been developed for studying gene function in this useful organism.Morpholino is the most widely used reagent to knock down target gene expression post-transcriptionally.For a long time,targeted genome modification has been heavily relied on large-scale traditional forward genetic screens,such as ENU（N-ethyl-N-nitrosourea） mutagenesis derived TILLING（Targeting Induced Local Lesions IN Genomes） strategy and pseudo-typed retrovirus mediated insertional mutagenesis.Recently,engineered endonucleases,including ZFNs（zinc finger nucleases） and TALENs（transcription activator-like effector nucleases）,provide new and efficient strategies to directly generate site-specific indel mutations by inducing double strand breaks in target genes.Here we summarize the major reverse genetic approaches for loss-of-function studies used and emerging in zebrafish,including strategies based on genome-wide mutagenesis and methods for site-specific gene targeting.Future directions and expectations will also be discussed.展开更多
Vascular endothelial growth factor A（Vegfa） signaling regulates vascular development during embryogenesis and organ formation.However,the signaling mechanisms that govern the formation of various arteries/veins in v...Vascular endothelial growth factor A（Vegfa） signaling regulates vascular development during embryogenesis and organ formation.However,the signaling mechanisms that govern the formation of various arteries/veins in various tissues are incompletely understood.In this study,we utilized transcription activator-like effector nuclease（TALEN） to generate zebrafish vegfaa mutants.vegfaa^-/- embryos are embryonic lethal,and display a complete loss of the dorsal aorta（DA） and expansion of the cardinal vein.Activation of Vegfa signaling expands the arterial cell population at the expense of venous cells during vasculogenesis of the axial vessels in the trunk.Vegfa signaling regulates endothelial cell（EC） proliferation after arterial-venous specification.Vegfa deficiency and overexpression inhibit the formation of tip cell filopodia and interfere with the pathfinding of intersegmental vessels（ISVs）.In the head vasculature,vegfaa^-/- causes loss of a pair of mesencephalic veins（MsVs） and central arteries（CtAs）,both of which usually dvelop via sprouting angiogenesis.Our results indicate that Vegfa signaling induces the formation of the DA at the expense of the cardinal vein during the trunk vasculogenesis,and that Vegfa is required for the angiogenic formation of MsVs and CtAs in the brain.These findings suggest that Vegfa signaling governs the formation of diverse arteries/veins by distinct cellular mechanisms in vertebrate vasculatures.展开更多
基金supported financially by the National Basic Research Program of China(973 Program)(Nos. 2009CB918702 and 2012CB825504)the National Natural Science Foundation of China(Nos.31201007,31271573 and 31071087)
文摘Precise modifications of complex genomes at the single nucleotide level have been one of the big goals for scientists working in basic and applied genetics,including biotechnology,drug development,gene therapy and synthetic biology.However,the relevant techniques for making these manipulations in model organisms and human cells have been lagging behind the rapid high throughput studies in the post-genomic era with a bottleneck of low efficiency,time consuming and laborious manipulation,and off-targeting problems.Recent discoveries of TALEs（transcription activator-like effectors） coding system and CRISPR（clusters of regularly interspaced short palindromic repeats） immune system in bacteria have enabled the development of customized TALENs（transcription activator-like effector nucleases） and CRISPR/Cas9 to rapidly edit genomic DNA in a variety of cell types,including human cells,and different model organisms at a very high efficiency and specificity.In this review,we first briefly summarize the development and applications of TALENs and CRISPR/Cas9-mediated genome editing technologies;compare the advantages and constraints of each method;particularly,discuss the expected applications of both techniques in the field of site-specific genome modification and stem cell based gene therapy;finally, propose the future directions and perspectives for readers to make the choices.
基金supported by the grants from the 973 Program(Nos.2009CB918702 and 2012CB945101)the NSFC(Nos.31071087 and 31100889)+1 种基金W.-M.D.is supported by NIH grant R01GM072562National Science Foundation of USA(IOS-1052333)
文摘Technology development has always been one of the forces driving breakthroughs in biomedical research. Since the time of Thomas Morgan, Drosophilists have, step by step, developed powerful genetic tools for manipulating and functionally dissecting the Drosophila genome, but room for improving these technologies and developing new techniques is still large, especially today as biologists start to study systematically the functional genomics of different model organisms, including humans, in a high-throughput manner. Here, we report, for the first time in Drosophila, a rapid, easy, and highly specific method for modifying the Drosophila genome at a very high efficiency by means of an improved transcription activator-like effector nuclease （TALEN） strategy. We took advantage of the very recently developed ＂unit assembly＂ strategy to assemble two pairs of specific TALENs designed to modify the yellow gene （on the sex chromosome） and a novel autosomal gene. The mRNAs of TALENs were subsequently injected into Drosophila embryos. From 31.2% of the injected Fo fertile flies, we detected inheritable modification involving the yellow gene. The entire process from construction of specific TALENs to detection of inheritable modifications can be accomplished within one month. The potential applications of this TALEN-mediated genome modification method in Drosophila are discussed.
基金supported by the National Basic Research Development Program of China (2011CBA00400 and 2011CB809102)the CAS Strategic Priority Research Program of China (XDB02050400)+2 种基金the National Key Technology R&D Program of China (2014BAI03B00)the CAS Hundreds of Talents Program of China (to Z.Q. and Q.S.)the National Science Foundation of China (91232712)
文摘Gene editing in model organisms has provided critical insights into brain development and diseases. Here, we report the generation of a cynomolgus monkey （Macaca fascicularis） carrying MECP2 mutations using transcription activator-like effector nucleases （TALENs）-mediated gene targeting. After injecting TALENs mRNA into monkey zygotes achieved by in vitro fertilization and embryo transplantation into surrogate monkeys, we obtained one male newborn monkey with an MECP2 deletion caused by frame- shifting mutation in various tissues. The monkey carrying the MECP2 mutation failed to survive after birth, due to either the toxicity of TALENs or the critical requirement of MECP2 for neural development. The level of MeCP2 protein was essentially depleted in the monkey＇s brain. This study demonstrates the feasibility of introducing genetic mutations in non-human primates by site-specific gene-editing methods.
基金provided by the grant(2013-33522-21091 to B.Y.) from the USDA Biotechnology Risk Assessment program
文摘Over the last decades,much endeavor has been made to advance genome editing technology due to its promising role in both basic and synthetic biology.The breakthrough has been made in recent years with the advent of sequence-specific endonucleases,especially zinc finger nucleases（ZFNs）,transcription activator-like effector nucleases（TALENs） and clustered regularly interspaced short palindromic repeats（CRISPRs） guided nucleases（e.g.,Cas9）.In higher eukaryotic organisms,site-directed mutagenesis usually can be achieved through non-homologous end-joining（NHEJ） repair to the DNA double-strand breaks（DSBs） caused by the exogenously applied nucleases.However,site-specific gene replacement or genuine genome editing through homologous recombination（HR） repair to DSBs remains a challenge.As a proof of concept gene replacement through TALEN-based HR in rice（Oryza sativa）,we successfully produced double point mutations in rice acetolactate synthase gene（OsALS） and generated herbicide resistant rice lines by using TALENs and donor DNA carrying the desired mutations.After ballistic delivery into rice calli of TALEN construct and donor DNA,nine HR events with different genotypes of OsALS were obtained in T_0 generation at the efficiency of 1.4%—6.3%from three experiments.The HRmediated gene edits were heritable to the progeny of T_1 generation.The edited T_1 plants were as morphologically normal as the control plants while displayed strong herbicide resistance.The results demonstrate the feasibility of TALEN-mediated genome editing in rice and provide useful information for further genome editing by other nuclease-based genome editing platforms.
基金supported by a Collaborative Funding Grant from North Carolina Biotechnology Center and Syngenta Biotechnology (2016-CFG-8003)startup funds provided by East Carolina University and University of Maryland to Y.Q.a grant from the National Science Foundation (IOS-1339209)
文摘Breakthroughs in the generation of programmable sequence-specific nucleases (SSNs), such as zinc finger nucleases (ZFNs),TAL effector nucleases (TALENs) and the RNA-directed nuclease CRISPR-associated protein 9 (Cas9), have greatly increased the ease of plant genome engineering (Voytas, 2013; Malzahn et al.,2017). Programmable SSNs introduce a DNA double-strand break
基金supported by the National Basic Research Program of China(973 Program)(2015CB554103 and 2011CBA01004)
文摘The transcription activator-like effector nuclease （TALEN） technique combined with the somatic cel nuclear transfer （SCNT） method has been successfuly applied for creating geneticaly modiifed pigs. However, methods for isolating cels with bialelic indels requires further improvement because of the relatively low enrichment efifciency of mutated somatic cels. Moreover, little is known regarding the off-target effects of the TALEN system and the heredity of TALEN-modiifed pigs. In this study, an efifcient method to increase the enrichment efifciency of TALEN-mediated bialelic knockout （KO） cels was established, and corresponding geneticaly modiifed pigs with the expected genotype were generated whose off-target effect, fertility and heredity characteristics were aslo evaluated. Two TALEN pairs were constructed to target the porcine α-1,3-galactosyltransferase （GGTA1） gene locus. TALEN mRNA was transfected into the ear ifbroblasts folowed by the enrichment of α-Gal nul cels of minipigs using isolectin B4 （IB4） lectin and magnetic beads. A total of 115 cel colonies were formed and validated to beGGTA1 KO cels by sequencing and 10 bialelic KO cel colonies were used as nuclear donors for SCNT. ThirtyGGTA1 bialelic KO piglets were successfuly delivered and grew normaly. Seventeen potential off-target sites were investigated, and no off-target events were detected in the live piglets. To determine the fertility and heredity characteristics of TALEN-modiifed pigs, 10 mature founders were mated with each other and the mutations were determined to be transmitted to the F1 piglets. We established a robust and safe technology for developing geneticaly modiifed pig lines with expected genotypes for agricultural breeding and biomedical application.
基金This work was supported in part by the ＂Reproductive health and major birth defects prevention and control research＂ Key Special Fund （No. 2016YFC1000601）, the National Natural Science Foundation of China （Grant Nos. 31371521, 81370766, 81401254, 81570101, 81671121, 31601187, 81521002）, the Guangdong Province Science and Technology Project （2014TQ01R683, 2017A020 214005, 2016A020216023, 2015A030310119, 2016B030229008）, the Bureau of Science and Technology of Guangzhou Municipality （201505011111498）, the ＂Reproductive health and major birth defects prevention and control research＂ Key Special Fund （Nos. 2016YFC1000201 and 2016YFC1000302）, the Ministry of Science and Technology of China Grants （973 program 2014CB943203）, and the Beijing Nova Program （xxjh2015011）.
文摘Mitochondrial diseases are maternally inherited hetero- geneous disorders that are primarily caused by mitochondrial DNA （mtDNA） mutations. Depending on the ratio of mutant to wild-type mtDNA, known as heteroplasmy, mitochondrial defects can result in a wide spectrum of clinical manifestations. Mitochondria-targeted endonucleases provide an alternative avenue for treating mitochondrial disorders via targeted destruc- tion of the mutant mtDNA and induction of heteroplasmic shifting. Here, we generated mitochondrial disease patient-specific induced pluripotent stem cells （MiPSCs） that harbored a high proportion of m.3243A〉G mtDNA mutations and caused mitochondrial encephalomyopathy and stroke-like episodes （MELAS）. We engineered mitochondrial-targeted transcription activator-like effector nucleases （mitoTALENs） and successfully eliminated the m.3243A〉G mutation in MiPSCs. Off-target mutagenesis was not detected in the targeted MiPSC clones. Utilizing a dual fluorescence iPSC reporter cell line expressing a 3243G mutant mtDNA sequence in the nuclear genome, mitoTALENs displayed a significantly limited ability to target the nuclear genome compared with nuclear-localized TALENs. Moreover, genetically rescued MiPSCs displayed normal mitochondrial respiration and energy production. Moreover, neuronal progenitor cells differentiated from the rescued MiPSCs also demonstrated normal metabolic profiles. Further- more, we successfully achieved reduction in the human m.3243A〉G mtDNA mutation in porcine oocytes via injection of mitoTALEN mRNA. Our study shows the great potential for using mitoTALENs for specific targeting of mutant mtDNA both in iPSCs and mammalian oocytes, which not only provides a new avenue for studying mitochondrial biology and disease but also suggests a potential therapeutic approach for the treatment of mitochondrial disease, as well as the prevention of germline transmission of mutant mtDNA.
基金the National Institutes of Health R21OD019934(KL)and U42OD011140(RSP)
文摘Pigs are an important resource in agriculture and serve as a model for human diseases. Due to their physiological and anatomical similarities with humans, pigs can recapitulate symptoms of human diseases, making them a useful model in biomedicine. However, in the past pig models have not been widely used partially because of the difficulty in genetic modification. The lack of true embryonic stem cells in pigs forced researchers to utilize genetic modification in somatic cells and somatic cell nuclear transfer(SCNT) to generate genetically engineered(GE) pigs carrying site-specific modifications. Although possible, this approach is extremely inefficient and GE pigs born through this method often presented developmental defects associated with the cloning process. Advancement in the gene-editing systems such as Zinc-Finger Nucleases(ZFNs), Transcription activator-like effector nucleases(TALENs), and the Clustered regularly interspaced short palindromic repeat(CRISPR)/CRISPR-associated 9(Cas9) system have dramatically increased the efficiency of producing GE pigs. These gene-editing systems, specifically engineered endonucleases, are based on inducing double-stranded breaks(DSBs) at a specific location, and then site-specific modifications can be introduced through one of the two DNA repair pathways: non-homologous end joining(NHEJ) or homology direct repair(HDR).Random insertions or deletions(indels) can be introduced through NHEJ and specific nucleotide sequences can be introduced through HDR, if donor DNA is provided. Use of these engineered endonucleases provides a higher success in genetic modifications, multiallelic modification of the genome, and an opportunity to introduce site-specific modifications during embryogenesis, thus bypassing the need of SCNT in GE pig production. This review will provide a historical prospective of GE pig production and examples of how the gene-editing system, led by engineered endonucleases, have improved GE pig production. We wil also present some of our current progress relate
基金partially supported by the grants from National Program on Key Basic Research Project(973 program)(Nos.2012CB945101 and 201 ICBAO 1000)National Natural Science Foundation of China(NSFC)(Nos. 31110103904 and 30730056)
文摘Zebrafish（Danio rerio） is a well-established vertebrate animal model.A comprehensive collection of reverse genetics tools has been developed for studying gene function in this useful organism.Morpholino is the most widely used reagent to knock down target gene expression post-transcriptionally.For a long time,targeted genome modification has been heavily relied on large-scale traditional forward genetic screens,such as ENU（N-ethyl-N-nitrosourea） mutagenesis derived TILLING（Targeting Induced Local Lesions IN Genomes） strategy and pseudo-typed retrovirus mediated insertional mutagenesis.Recently,engineered endonucleases,including ZFNs（zinc finger nucleases） and TALENs（transcription activator-like effector nucleases）,provide new and efficient strategies to directly generate site-specific indel mutations by inducing double strand breaks in target genes.Here we summarize the major reverse genetic approaches for loss-of-function studies used and emerging in zebrafish,including strategies based on genome-wide mutagenesis and methods for site-specific gene targeting.Future directions and expectations will also be discussed.
基金supported by grants from the National Basic Research Program of China (MOST945301)the National Science Foundation of China(Nos.81170152,31471357,and 31530044)the Natural Science Foundation of Science and Technology Commission of Shanghai Municipality(13ZR1457500)
文摘Vascular endothelial growth factor A（Vegfa） signaling regulates vascular development during embryogenesis and organ formation.However,the signaling mechanisms that govern the formation of various arteries/veins in various tissues are incompletely understood.In this study,we utilized transcription activator-like effector nuclease（TALEN） to generate zebrafish vegfaa mutants.vegfaa^-/- embryos are embryonic lethal,and display a complete loss of the dorsal aorta（DA） and expansion of the cardinal vein.Activation of Vegfa signaling expands the arterial cell population at the expense of venous cells during vasculogenesis of the axial vessels in the trunk.Vegfa signaling regulates endothelial cell（EC） proliferation after arterial-venous specification.Vegfa deficiency and overexpression inhibit the formation of tip cell filopodia and interfere with the pathfinding of intersegmental vessels（ISVs）.In the head vasculature,vegfaa^-/- causes loss of a pair of mesencephalic veins（MsVs） and central arteries（CtAs）,both of which usually dvelop via sprouting angiogenesis.Our results indicate that Vegfa signaling induces the formation of the DA at the expense of the cardinal vein during the trunk vasculogenesis,and that Vegfa is required for the angiogenic formation of MsVs and CtAs in the brain.These findings suggest that Vegfa signaling governs the formation of diverse arteries/veins by distinct cellular mechanisms in vertebrate vasculatures.
