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Atsuo Ogura - One of the best experts on this subject based on the ideXlab platform.
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a new dynamic era for somatic cell Nuclear Transfer
Trends in Biotechnology, 2016Co-Authors: Pasqualino Loi, Domenico Iuso, Marta Czernik, Atsuo OguraAbstract:Cloning animals by somatic cell Nuclear Transfer (SCNT) has remained an uncontrollable process for many years. High rates of embryonic losses, stillbirths, and postnatal mortality have been typical outcomes. These developmental problems arise from abnormal genomic reprogramming: the capacity of the oocyte to reset the differentiated memory of a somatic cell. However, effective reprogramming strategies are now available. These target the whole genome or single domains such as the Xist gene, and their effectiveness has been validated with the ability of experimental animals to develop to term. Thus, SCNT has become a controllable process that can be used to ‘rescue' endangered species, and for biomedical research such as therapeutic cloning and the isolation of induced pluripotent stem cells (iPSCs).
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recent advancements in cloning by somatic cell Nuclear Transfer
Philosophical Transactions of the Royal Society B, 2013Co-Authors: Atsuo Ogura, Kimiko Inoue, Teruhiko WakayamaAbstract:Somatic cell Nuclear Transfer (SCNT) cloning is the sole reproductive engineering technology that endows the somatic cell genome with totipotency. Since the first report on the birth of a cloned sheep from adult somatic cells in 1997, many technical improvements in SCNT have been made by using different epigenetic approaches, including enhancement of the levels of histone acetylation in the chromatin of the reconstructed embryos. Although it will take a considerable time before we fully understand the nature of genomic programming and totipotency, we may expect that somatic cell cloning technology will soon become broadly applicable to practical purposes, including medicine, pharmaceutical manufacturing and agriculture. Here we review recent progress in somatic cell cloning, with a special emphasis on epigenetic studies using the laboratory mouse as a model.
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inefficient reprogramming of the hematopoietic stem cell genome following Nuclear Transfer
Journal of Cell Science, 2006Co-Authors: Kimiko Inoue, Narumi Ogonuki, Hiromi Miki, Michiko Hirose, Shinichi Noda, Fugaku Aoki, Hiroyuki Miyoshi, Atsuo OguraAbstract:In general, cloning undifferentiated preimplantation embryos (blastomeres) or embryonic stem cells is more efficient than cloning differentiated somatic cells. Therefore, there has been an assumption that tissue-specific stem cells might serve as efficient donors for Nuclear Transfer because of the undifferentiated state of their genome. Here, we show that this is not the case with adult hematopoietic stem cells (HSCs). Although we have demonstrated for the first time that mouse HSCs can be cloned to generate offspring, the birth rates (0-0.7%) were lowest among the clones tested (cumulus, immature Sertoli and fibroblast cells). Only 6% of reconstructed embryos reached the morula or blastocyst stage in vitro (versus 46% for cumulus clones; P -10 ). Transcription and gene expression analyses of HSC clone embryos revealed that they initiated zygotic gene activation (ZGA) at the appropriate timing, but failed to activate five out of six important embryonic genes examined, including Hdac1 (encoding histone deacetylase 1), a key regulator of subsequent ZGA. These results suggest that the HSC genome has less plasticity than we imagined, at least in terms of reprogrammability in the ooplasm after Nuclear Transfer.
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inefficient reprogramming of the hematopoietic stem cell genome following Nuclear Transfer
Journal of Cell Science, 2006Co-Authors: Kimiko Inoue, Narumi Ogonuki, Hiromi Miki, Michiko Hirose, Shinichi Noda, Fugaku Aoki, Hiroyuki Miyoshi, Jinmoon Kim, Atsuo OguraAbstract:In general, cloning undifferentiated preimplantation embryos (blastomeres) or embryonic stem cells is more efficient than cloning differentiated somatic cells. Therefore, there has been an assumption that tissue-specific stem cells might serve as efficient donors for Nuclear Transfer because of the undifferentiated state of their genome. Here, we show that this is not the case with adult hematopoietic stem cells (HSCs). Although we have demonstrated for the first time that mouse HSCs can be cloned to generate offspring, the birth rates (0-0.7%) were lowest among the clones tested (cumulus, immature Sertoli and fibroblast cells). Only 6% of reconstructed embryos reached the morula or blastocyst stage in vitro (versus 46% for cumulus clones; P
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analysis of the mechanism for chromatin remodeling in embryos reconstructed by somatic Nuclear Transfer
Biology of Reproduction, 2002Co-Authors: Atsuo Ogura, Jinmoon Kim, Masao Nagata, Fugaku AokiAbstract:The objective of the present study was to understand the molecular/biochemical nature of chromatin remodeling that occurs in the somatic nuclei Transferred into oocytes. We produced the reconstructed mouse embryos by two different protocols of Nuclear Transfer. The nucleus of a cumulus cell was Transferred into enucleated unfertilized oocytes (Transferred before activation, TA protocol) or activated oocytes (activated before Transfer, AT protocol). More than half (56.1%) of the embryos reconstructed using the TA protocol developed to the morula/blastocyst stage, whereas very few (1.0%) of the embryos reconstructed using the AT protocol reached the morula/blastocyst stage. These embryos were analyzed for the events associated with transcriptional regulation. Changes in transcriptional activity, Nuclear accumulation of TATA box binding protein (TBP), and DNase I sensitivity were examined after Nuclear Transfer. In the embryos reconstructed by TA protocol, all of these events occurred in a manner similar to that in the control diploid parthenogenetic embryos. The transcriptional activity was silenced after Nuclear Transfer and resumed at the late 1-cell stage. TBP was displaced and subsequently accumulated at the early and the late 1-cell stage, respectively. DNase I sensitivity was increased and then decreased at the early and late 1-cell stage, respectively. In contrast, embryos reconstructed using the AT protocol did not show such changes in transcriptional activity, TBP accumulation, and DNase I sensitivity. These events would be necessary for differentiated nuclei to restore totipotency and are useful indices to evaluate successful chromatin remodeling.
Teruhiko Wakayama - One of the best experts on this subject based on the ideXlab platform.
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recent advancements in cloning by somatic cell Nuclear Transfer
Philosophical Transactions of the Royal Society B, 2013Co-Authors: Atsuo Ogura, Kimiko Inoue, Teruhiko WakayamaAbstract:Somatic cell Nuclear Transfer (SCNT) cloning is the sole reproductive engineering technology that endows the somatic cell genome with totipotency. Since the first report on the birth of a cloned sheep from adult somatic cells in 1997, many technical improvements in SCNT have been made by using different epigenetic approaches, including enhancement of the levels of histone acetylation in the chromatin of the reconstructed embryos. Although it will take a considerable time before we fully understand the nature of genomic programming and totipotency, we may expect that somatic cell cloning technology will soon become broadly applicable to practical purposes, including medicine, pharmaceutical manufacturing and agriculture. Here we review recent progress in somatic cell cloning, with a special emphasis on epigenetic studies using the laboratory mouse as a model.
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significant improvement of mouse cloning technique by treatment with trichostatin a after somatic Nuclear Transfer
Biochemical and Biophysical Research Communications, 2006Co-Authors: Satoshi Kishigami, Sayaka Wakayama, Nguyen Van Thuan, Takafusa Hikichi, Eiji Mizutani, Hiroshi Ohta, Teruhiko WakayamaAbstract:The low success rate of animal cloning by somatic cell Nuclear Transfer (SCNT) is believed to be associated with epigenetic errors including abnormal DNA hypermethylation. Recently, we elucidated by using round spermatids that, after Nuclear Transfer, treatment of zygotes with trichostatin A (TSA), an inhibitor of histone deacetylase, can remarkably reduce abnormal DNA hypermethylation depending on the origins of Transferred nuclei and their genomic regions [S. Kishigami, N. Van Thuan, T. Hikichi, H. Ohta, S. Wakayama. E. Mizutani, T. Wakayama, Epigenetic abnormalities of the mouse paternal zygotic genome associated with microinsemination of round spermatids, Dev. Biol. (2005) in press]. Here, we found that 5–50 nM TSA-treatment for 10 h following oocyte activation resulted in more efficient in vitro development of somatic cloned embryos to the blastocyst stage from 2- to 5-fold depending on the donor cells including tail tip cells, spleen cells, neural stem cells, and cumulus cells. This TSA-treatment also led to more than 5-fold increase in success rate of mouse cloning from cumulus cells without obvious abnormality but failed to improve ES cloning success. Further, we succeeded in establishment of Nuclear Transfer-embryonic stem (NT-ES) cells from TSA-treated cloned blastocyst at a rate three times higher than those from untreated cloned blastocysts. Thus, our data indicate that TSA-treatment after SCNT in mice can dramatically improve the practical application of current cloning techniques.
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establishment of male and female Nuclear Transfer embryonic stem cell lines from different mouse strains and tissues
Biology of Reproduction, 2005Co-Authors: Sayaka Wakayama, Satoshi Kishigami, Takafusa Hikichi, Eiji Mizutani, Hiroshi Ohta, Nguyen Van Thuan, Masashi Miyake, Teruhiko WakayamaAbstract:Nuclear Transfer can be used to generate embryonic stem cell lines from somatic cells, and these have great potential in regenerative medicine. However, it is still unclear whether any individual or cell type can be used to generate such lines. Here, we tested seven different male and female mouse genotypes and three cell types as sources of nuclei to determine the efficiency of establishing Nuclear Transfer embryonic stem cell lines. Lines were successfully established from all sources. Cumulus cell nuclei from F(1) mouse genotypes showed a significantly higher cumulative establishment rate from reconstructed oocytes than from other cells; however, there were no genotype differences in success rates from cloned blastocysts. Thus, the overall success depends on preimplantation development, and, once embryos have reached the blastocyst stage, the genotype differences disappear. All mouse genotypes that were tested demonstrated at least one cell line that subsequently contributed to germline transmission in chimeric mice, so these cell lines clearly possess the same potential as embryonic stem cells derived from fertilized embryos. Thus, Nuclear Transfer embryonic stem cells can be generated relatively easily from a variety of inbred mouse genotypes and cell types of both sexes, even though it may be more difficult to generate clones directly.
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propagation of an infertile hermaphrodite mouse lacking germ cells by using Nuclear Transfer and embryonic stem cell technology
Proceedings of the National Academy of Sciences of the United States of America, 2005Co-Authors: Sayaka Wakayama, Satoshi Kishigami, Nguyen Van Thuan, Takafusa Hikichi, Eiji Mizutani, Hiroshi Ohta, Ryuzo Yanagimachi, Teruhiko WakayamaAbstract:Animals generated by systematic mutagenesis and routine breeding are often infertile because they lack germ cells, and maintenance of such lines of animals has been impossible. We found a hermaphrodite infertile mouse in our colony, a genetic male with an abnormal Y chromosome lacking developing germ cells. We tried to clone this mouse by conventional Nuclear Transfer but without success. ES cells produced from blastocysts, which had been cloned by using somatic cell Nuclear Transfer (ntES cells) from this mouse, were also unable to produce offspring when injected into enucleated oocytes. Although we were able to produce two chimeric offspring using these ntES cells by tetraploid complementation, they were infertile, because they also lacked developing germ cells. However, when such ntES cells were injected into normal diploid blastocysts, many chimeric offspring were produced. One such male offspring transmitted hermaphrodite mouse genes to fertile daughters via X chromosome-bearing sperm. Thus, ntES cells were used to propagate offspring from infertile mice lacking germ cells.
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differentiation of embryonic stem cell lines generated from adult somatic cells by Nuclear Transfer
Science, 2001Co-Authors: Teruhiko Wakayama, Viviane Tabar, Ivan Rodriguez, Anthony C F Perry, Lorenz Studer, Peter T MombaertsAbstract:Embryonic stem (ES) cells are fully pluripotent in that they can differentiate into all cell types, including gametes. We have derived 35 ES cell lines via Nuclear Transfer (ntES cell lines) from adult mouse somatic cells of inbred, hybrid, and mutant strains. ntES cells contributed to an extensive variety of cell types, including dopaminergic and serotonergic neurons in vitro and germ cells in vivo. Cloning by Transfer of ntES cell nuclei could result in normal development of fertile adults. These studies demonstrate the full pluripotency of ntES cells.
Ian Wilmut - One of the best experts on this subject based on the ideXlab platform.
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effect of limited dna methylation reprogramming in the normal sheep embryo on somatic cell Nuclear Transfer
Biology of Reproduction, 2004Co-Authors: Nathalie Beaujean, Ian Wilmut, Jane E Taylor, John Gardner, Richard R Meehan, L E YoungAbstract:Active demethylation of cytosine residues in the sperm genome before forming a functional zygotic nucleus is thought to be an important function of the oocyte cytoplasm for subsequent embryonic development in the mouse. Conversely, this event does not occur in the sheep or rabbit zygote and occurs only partially in the cow. The aim of this study was to investigate the effect of limited methylation reprogramming in the normal sheep embryo on reprogramming somatic nuclei. Sheep fibroblast somatic nuclei were partially demethylated after electrofusion with recipient sheep oocytes and undergo a stepwise passive loss of DNA methylation during early development, as determined by 5-methylcytosine immunostaining on interphase embryonic nuclei. A similar decrease takes place with in vivoderived sheep embryos up to the eight-cell stage, although Nuclear Transfer embryos exhibit a consistently higher level of methylation at each stage. Between the eight-cell and blastocyst stages, DNA methylation levels in Nuclear Transfer embryos are comparable with those derived in vivo, but the distribution of methylated DNA is abnormal in a high proportion. By correlating DNA methylation with developmental potential at individual stages, our results suggest that somatic nuclei that do not undergo rapid reorganization of their DNA before the first mitosis fail to develop within two to three cell cycles and that the observed methylation defects in early cleavage stages more likely occur as a direct consequence of failed Nuclear reorganization than in failed demethylation capacity. However, because only embryos with reorganized chromatin appear to survive the 16cell and morula stages, failure to demethylate the trophectoderm cells of the blastocyst is likely to directly impact on developmental potential by altering programmed patterns of gene expression in extra‐embryonic tissues. Thus, both remodeling of DNA and epigenetic reprogramming appear critical for development of both fertilized and Nuclear Transfer embryos. developmental biology, early development, embryo, gene regulation
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germinal vesicle material is essential for nucleus remodeling after Nuclear Transfer
Biology of Reproduction, 2002Co-Authors: Shaorong Gao, B Gasparrini, Michelle Mcgarry, Tricia Ferrier, Judy Fletcher, Linda Harkness, Paul A De Sousa, Ian WilmutAbstract:Successful cloning by Nuclear Transfer has been reported with somatic or embryonic stem (ES) cell nucleus injection into enucleated mouse metaphase II oocytes. In this study, we enucleated mouse oocytes at the germinal vesicle (GV) or pro-metaphase I (pro-MI) stage and cultured the cytoplasm to the MII stage. Nuclei from cells of the R1 ES cell line were injected into both types of cytoplasm to evaluate developmental potential of resulting embryos compared to MII cytoplasmic injection. Immunocytochemical staining revealed that a spindle started to organize 30 min after nucleus injection into all three types of cytoplasm. A well-organized bipolar spindle resembling an MII spindle was present in both pro-MI and MII cytoplasm 1 h after injection with ES cells. However, in the mature GV cytoplasm, chromosomes were distributed throughout the cytoplasm and a much bigger spindle was formed. Pseudopronucleus formation was observed in pro-MI and MII cytoplasm after activation treatment. Although no pronucleus formation was found in GV cytoplasm, chromosomes segregated into two groups in response to activation. Only 8.1% of reconstructed embryos with pro-MI cytoplasm developed to the morula stage after culture in CZB medium. In contrast, 53.5% of embryos reconstructed with MII cytoplasm developed to the morula/blastocyst stage, and 5.3% of Transferred embryos developed to term. These results indicate that GV material is essential for nucleus remodeling after Nuclear Transfer. early development, embryo, gamete biology, implantation, oocyte development
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Somatic cell Nuclear Transfer
Nature, 2002Co-Authors: Ian Wilmut, L. A. Paterson, D. N. Wells, P. A. Sousa, Tsu-jae King, Nathalie Beaujean, Andras Dinnyes, L E YoungAbstract:Cloning by Nuclear Transfer from adult somatic cells is a remarkable demonstration of developmental plasticity. When a nucleus is placed in oocyte cytoplasm, the changes in chromatin structure that govern differentiation can be reversed, and the nucleus can be made to control development to term.
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mitochondrial dna genotypes in Nuclear Transfer derived cloned sheep
Nature Genetics, 1999Co-Authors: Matthew J Evans, Ian Wilmut, Cagan Gurer, John D Loike, Angelika Schnieke, Eric A SchonAbstract:Eukaryotic cells contain two distinct genomes. One is located in the nucleus (nDNA) and is transmitted in a mendelian fashion, whereas the other is located in mitochondria (mtDNA) and is transmitted by maternal inheritance. Cloning of mammals1,2,3,4,5,6 typically has been achieved via Nuclear Transfer, in which a donor somatic cell is fused by electoporation with a recipient enucleated oocyte. During this whole-cell electrofusion, nDNA as well as mtDNA ought to be Transferred to the oocyte7,8. Thus, the cloned progeny should harbour mtDNAs from both the donor and recipient cytoplasms, resulting in heteroplasmy. Although the confirmation of Nuclear Transfer has been established using somatic cell-specific nDNA markers, no similar analysis of the mtDNA genotype has been reported. We report here the origin of the mtDNA in Dolly, the first animal cloned from an established adult somatic cell line, and in nine other Nuclear Transfer-derived sheep generated from fetal cells. The mtDNA of each of the ten Nuclear-Transfer sheep was derived exclusively from recipient enucleated oocytes, with no detectable contribution from the respective somatic donor cells. Thus, although these ten sheep are authentic Nuclear clones, they are in fact genetic chimaeras, containing somatic cell-derived Nuclear DNA but oocyte-derived mtDNA.
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sheep cloned by Nuclear Transfer from a cultured cell line
Nature, 1996Co-Authors: Keith H S Campbell, Jim Mcwhir, W A Ritchie, Ian WilmutAbstract:Nuclear Transfer has been used in mammals as both a valuable tool in embryological studies and as a method for the multiplication of 'elite' embryos. Offspring have only been reported when early embryos, or embryo-derived cells during primary culture, were used as Nuclear donors. Here we provide the first report, to our knowledge, of live mammalian offspring following Nuclear Transfer from an established cell line. Lambs were born after cells derived from sheep embryos, which had been cultured for 6 to 13 passages, were induced to quiesce by serum starvation before Transfer of their nuclei into enucleated oocytes. Induction of quiescence in the donor cells may modify the donor chromatin structure to help Nuclear reprogramming and allow development. This approach will provide the same powerful opportunities for analysis and modification of gene function in livestock species that are available in the mouse through the use of embryonic stem cells.
Kimiko Inoue - One of the best experts on this subject based on the ideXlab platform.
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recent advancements in cloning by somatic cell Nuclear Transfer
Philosophical Transactions of the Royal Society B, 2013Co-Authors: Atsuo Ogura, Kimiko Inoue, Teruhiko WakayamaAbstract:Somatic cell Nuclear Transfer (SCNT) cloning is the sole reproductive engineering technology that endows the somatic cell genome with totipotency. Since the first report on the birth of a cloned sheep from adult somatic cells in 1997, many technical improvements in SCNT have been made by using different epigenetic approaches, including enhancement of the levels of histone acetylation in the chromatin of the reconstructed embryos. Although it will take a considerable time before we fully understand the nature of genomic programming and totipotency, we may expect that somatic cell cloning technology will soon become broadly applicable to practical purposes, including medicine, pharmaceutical manufacturing and agriculture. Here we review recent progress in somatic cell cloning, with a special emphasis on epigenetic studies using the laboratory mouse as a model.
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inefficient reprogramming of the hematopoietic stem cell genome following Nuclear Transfer
Journal of Cell Science, 2006Co-Authors: Kimiko Inoue, Narumi Ogonuki, Hiromi Miki, Michiko Hirose, Shinichi Noda, Fugaku Aoki, Hiroyuki Miyoshi, Atsuo OguraAbstract:In general, cloning undifferentiated preimplantation embryos (blastomeres) or embryonic stem cells is more efficient than cloning differentiated somatic cells. Therefore, there has been an assumption that tissue-specific stem cells might serve as efficient donors for Nuclear Transfer because of the undifferentiated state of their genome. Here, we show that this is not the case with adult hematopoietic stem cells (HSCs). Although we have demonstrated for the first time that mouse HSCs can be cloned to generate offspring, the birth rates (0-0.7%) were lowest among the clones tested (cumulus, immature Sertoli and fibroblast cells). Only 6% of reconstructed embryos reached the morula or blastocyst stage in vitro (versus 46% for cumulus clones; P -10 ). Transcription and gene expression analyses of HSC clone embryos revealed that they initiated zygotic gene activation (ZGA) at the appropriate timing, but failed to activate five out of six important embryonic genes examined, including Hdac1 (encoding histone deacetylase 1), a key regulator of subsequent ZGA. These results suggest that the HSC genome has less plasticity than we imagined, at least in terms of reprogrammability in the ooplasm after Nuclear Transfer.
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inefficient reprogramming of the hematopoietic stem cell genome following Nuclear Transfer
Journal of Cell Science, 2006Co-Authors: Kimiko Inoue, Narumi Ogonuki, Hiromi Miki, Michiko Hirose, Shinichi Noda, Fugaku Aoki, Hiroyuki Miyoshi, Jinmoon Kim, Atsuo OguraAbstract:In general, cloning undifferentiated preimplantation embryos (blastomeres) or embryonic stem cells is more efficient than cloning differentiated somatic cells. Therefore, there has been an assumption that tissue-specific stem cells might serve as efficient donors for Nuclear Transfer because of the undifferentiated state of their genome. Here, we show that this is not the case with adult hematopoietic stem cells (HSCs). Although we have demonstrated for the first time that mouse HSCs can be cloned to generate offspring, the birth rates (0-0.7%) were lowest among the clones tested (cumulus, immature Sertoli and fibroblast cells). Only 6% of reconstructed embryos reached the morula or blastocyst stage in vitro (versus 46% for cumulus clones; P
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birth of mice after Nuclear Transfer by electrofusion using tail tip cells
Molecular Reproduction and Development, 2000Co-Authors: Atsuo Ogura, Teruhiko Wakayama, Kimiko Inoue, Kaoru Takano, Ryuzo YanagimachiAbstract:Mice have been successfully cloned from cumulus cells, fibroblast cells, embryonic stem cells, and immature Sertoli cells only after direct injection of their nuclei into enucleated oocytes. This technical feature of mouse Nuclear Transfer differentiates it from that used in domestic species, where electrofusion is routinely used for Nuclear Transfer. To examine whether Nuclear Transfer by electrofusion can be applied to somatic cell cloning in the mouse, we electrofused tail tip fibroblast cells with enucleated oocytes, and then assessed the subsequent in vitro and in vivo development of the reconstructed embryos. The rate of successful Nuclear Transfer (fusion and Nuclear formation) was 68.8% (753/1094) and the rate of development into morulae/blastocysts was 40.8% (260/637). After embryo Transfer, seven (six males and one female; 2.5% per Transfer) normal fetuses were obtained at 17.5–21.5 dpc. These rates of development in vitro and in vivo are not significantly different from those after cloning by injection (44.7% to morulae/blastocysts and 4.8% to term). These results indicate that Nuclear Transfer by electrofusion is practical for mouse somatic cell cloning and provide an alternative method when injection of donor nuclei into recipient oocytes is technically difficult. Mol. Reprod. Dev. 57:55–59, 2000. © 2000 Wiley-Liss, Inc.
John B. Gurdon - One of the best experts on this subject based on the ideXlab platform.
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hira dependent h3 3 deposition is required for transcriptional reprogramming following Nuclear Transfer to xenopus oocytes
Epigenetics & Chromatin, 2012Co-Authors: Jerome Jullien, Carolina Astrand, Emmanuelle Szenker, Nigel Garrett, Genevieve Almouzni, John B. GurdonAbstract:Background Nuclear reprogramming is potentially important as a route to cell replacement and drug discovery, but little is known about its mechanism. Nuclear Transfer to eggs and oocytes attempts to identify the mechanism of this direct route towards reprogramming by natural components. Here we analyze how the reprogramming of nuclei transplanted to Xenopus oocytes exploits the incorporation of the histone variant H3.3.
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hira dependent h3 3 deposition is required for transcriptional reprogramming following Nuclear Transfer to xenopus oocytes
Epigenetics & Chromatin, 2012Co-Authors: Jerome Jullien, Carolina Astrand, Emmanuelle Szenker, Nigel Garrett, Genevieve Almouzni, John B. GurdonAbstract:Nuclear reprogramming is potentially important as a route to cell replacement and drug discovery, but little is known about its mechanism. Nuclear Transfer to eggs and oocytes attempts to identify the mechanism of this direct route towards reprogramming by natural components. Here we analyze how the reprogramming of nuclei transplanted to Xenopus oocytes exploits the incorporation of the histone variant H3.3. After Nuclear transplantation, oocyte-derived H3.3 but not H3.2, is deposited on several regions of the genome including rDNA, major satellite repeats, and the regulatory regions of Oct4. This major H3.3 deposition occurs in absence of DNA replication, and is HIRA-and transcription-dependent. It is necessary for the shift from a somatic- to an oocyte-type of transcription after Nuclear Transfer. This study demonstrates that the incorporation of histone H3.3 is an early and necessary step in the direct reprogramming of somatic cell nuclei by oocyte. It suggests that the incorporation of histone H3.3 is necessary during global changes in transcription that accompany changes in cell fate.
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reprogramming and development in Nuclear Transfer embryos and in interspecific systems
Current Opinion in Genetics & Development, 2012Co-Authors: Patrick Narbonne, Kei Miyamoto, John B. GurdonAbstract:Nuclear Transfer (NT) remains the most effective method to reprogram somatic cells to totipotency. Somatic cell Nuclear Transfer (SCNT) efficiency however remains low, but recurrent problems occurring in partially reprogrammed cloned embryos have recently been identified and some remedied. In particular, the trophectoderm has been identified as a lineage whose reprogramming success has a large influence on SCNT embryo development. Several interspecific hybrid and cybrid reprogramming systems have been developed as they offer various technical advantages and potential applications, and together with SCNT, they have led to the identification of a series of reprogramming events and responsible reprogramming factors. Interspecific incompatibilities hinder full exploitation of cross-species reprogramming systems, yet recent findings suggest that these may not constitute insurmountable obstacles.
