Somatic cell nuclear transfer

Wilmut, Ian; Beaujean, Nathalie; Sousa, Paul A. De; Dinnyés, András; King, Tim; Paterson, Lesley; Wells, David N.; Young, Lorraine

doi:10.1038/nature01079

Cited by 481 publications

(216 citation statements)

References 35 publications

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“…[19][20][21]. We were very surprised to initially uncover dramatic differences in the epigenetic reprogramming events occurring between sheep and mouse during normal preimplantation development (19).…”

Section: Discussionmentioning

confidence: 99%

The effect of interspecific oocytes on demethylation of sperm DNA

Beaujean

Taylor

McGarry

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

114

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In contrast to mice, in sheep no genome-wide demethylation of the paternal genome occurs within the first postfertilization cell cycle. This difference could be due either to an absence of a sheep demethylase activity that is present in mouse ooplasm or to an increased protection of methylated cytosine residues in sheep sperm. Here, we use interspecies intracytoplasmic sperm injection to demonstrate that sheep sperm DNA can be demethylated in mouse oocytes. Surprisingly, mouse sperm can also be demethylated to a limited extent in sheep oocytes. Our results suggest that the murine demethylation process is facilitated either by a spermderived factor or by male pronuclear chromatin composition.M ethylation of the DNA cytosine residues in CpG dinucleotides is part of the complex epigenetic mechanism that has evolved to silence genomic sequences where their transcription either is not required for development or may be detrimental to genomic stability (reviewed in refs. 1-3). DNA methylation also plays an important role in allele-specific repression at imprinted gene loci, regulating such processes as fetal growth and development as well as X inactivation (reviewed in refs. 4-6). Whereas the genome-wide methylation patterns and levels of differentiated somatic lineages remain largely constant, very dynamic changes have been reported to occur in the preimplantation embryo in association with the formation of pluripotent embryonic nuclei.After fertilization, the sperm and egg genomes are remodeled into pronuclei, which appose within the oocyte cytoplasm before the first embryonic mitosis. However, the highly condensed sperm chromatin requires extensive nuclear remodeling and protamine-histone exchange, unlike nucleosomal maternal chromatin. By using an antibody against 5-methylcytosine (5mC), the presumptive male pronucleus of mouse, rat, pig, human, and, to a lesser extent, cow embryos have been shown to actively demethylate before syngamy, whereas the female pronucleus retains genome-wide methylation (7-12). In contrast, active demethylation of the paternal genome is not observed in early sheep or rabbit embryos (with an intermediate state in the cow) (12), which suggests that it is not an obligate requirement for mammalian development. The discovery that the dramatic changes in DNA methylation associated with early formative events in the mouse embryo are not conserved in the sheep allows a unique opportunity to investigate the regulatory mechanisms involved. Mouse ooplasm can fully demethylate multiple male pronuclei in polyspermic embryos, which raises the question of whether the demethylating activity resides in the fertilized oocyte or is intimately associated with the sperm (10). We have now used interspecies intracytoplasmic sperm injection (ICSI) to mimic the events of normal fertilization and investigate whether species differences in the oocyte environment or sperm composition determines the extent of male pronuclear demethylation. Materials and MethodsAll animal procedures were under strict accordance with...

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Section: Discussionmentioning

confidence: 99%

The effect of interspecific oocytes on demethylation of sperm DNA

Beaujean

Taylor

McGarry

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

114

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“…Their success was probably due to the fact that they induced their cells into a quiescent state prior to nuclear transfer (Wilmut et al 2002). Using similar techniques, Wilmut was able to produce an adult sheep, famously known as 'Dolly', using nuclei derived from follicle cells ( Wilmut et al 1997).…”

Section: Reprogramming By Nuclear Transfermentioning

confidence: 95%

Pluripotency and nuclear reprogramming

Yamanaka

2008

Phil. Trans. R. Soc. B

148

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Embryonic stem cells are promising donor cell sources for cell transplantation therapy, which may in the future be used to treat various diseases and injuries. However, as is the case for organ transplantation, immune rejection after transplantation is a potential problem with this type of therapy. Moreover, the use of human embryos presents serious ethical difficulties. These issues may be overcome if pluripotent stem cells are generated from patients' somatic cells. Here, we review the molecular mechanisms underlying pluripotency and the currently known methods of inducing pluripotency in somatic cells.

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“…The ability of transplanted nuclei to promote normal development declines as development progresses in both amphibian and mammalian nuclear transfer experiments (2,3,6). Typically Ϸ1% of the nuclei of differentiated amphibian cells yield feeding tadpoles (4, 7) and Ͻ3% of cloned mammalian embryos develop into live births (8,9). In Amphibia, a substantial proportion of nuclear transplant (NT) embryos cleave abnormally as partially cleaved blastulae, which die within 24 h (2, 3).…”

mentioning

confidence: 99%

Epigenetic memory of active gene transcription is inherited through somatic cell nuclear transfer

Gurdon

2005

Proc. Natl. Acad. Sci. U.S.A.

122

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The transplantation of somatic cell nuclei to enucleated eggs has shown that genes can be reprogrammed to an embryonic pattern of expression, thereby indicating a reversal of their epigenetic state. However, in Xenopus nuclear transfer experiments using both endoderm and neuroectoderm donor cells, we have observed substantial overexpression of donor cell type-specific genes, both spatially and temporally, in the wrong cell type in some nuclear transplant embryos. For example, more than half of the embryos prepared from transplanted neuroectoderm nuclei overexpressed the neuroectodermal marker gene Sox2 to an excessive level in their endoderm cells. Because, in Xenopus, there is no transcription for the first 12 cell cycles, some somatic cell nuclei must remember a developmentally activated gene state and transmit this to their mitotic progeny in the absence of the conditions that induced that state. We also find that donor cell-specific genes are transcribed at an earlier stage than normal in an inappropriate cell type. This phenomenon of epigenetic memory applies to genes that are transcribed in donor nuclei; it does not influence those genes that are competent to be transcribed in nuclear transplant embryo tissue, but were not actually transcribed in donor nuclei at the time of nuclear transfer. We conclude that an epigenetic memory is established in differentiating somatic cells and applies to genes that are in a transcriptionally active state.Xenopus ͉ cloning

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Somatic cell nuclear transfer

Cited by 481 publications

References 35 publications

The effect of interspecific oocytes on demethylation of sperm DNA

The effect of interspecific oocytes on demethylation of sperm DNA

Pluripotency and nuclear reprogramming

Epigenetic memory of active gene transcription is inherited through somatic cell nuclear transfer

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