Abstract
Somatic cell nuclear transfer embryos exhibit extensive epigenetic abnormalities, including aberrant methylation and abnormal imprinted gene expression. In this study, a thorough analysis of X chromosome inactivation (XCI) was performed in both preimplantation and postimplantation nuclear transfer embryos. Cloned blastocysts reactivated the inactive somatic X chromosome, possibly in a gradient fashion. Analysis of XCI by Xist RNA and Eed protein localization revealed heterogeneity within cloned embryos, with some cells successfully inactivating an X chromosome and others failing to do so. Additionally, a significant proportion of cells contained more than two X chromosomes, which correlated with an increased incidence of tetraploidy. Imprinted XCI, normally found in preimplantation embryos and extraembryonic tissues, was not observed in blastocysts or placentae from later stage clones, although fetuses recapitulated the Xce effect. We conclude that, although SCNT embryos can reactivate, count, and inactivate X chromosomes, they are not able to regulate XCI consistently. These results illustrate the heterogeneity of epigenetic changes found in cloned embryos.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Biomarkers
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Blastocyst / physiology*
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Cell Lineage
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Chromosomal Proteins, Non-Histone / genetics
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Chromosomal Proteins, Non-Histone / metabolism
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Cloning, Organism
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Cyclin-Dependent Kinases / genetics
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Cyclin-Dependent Kinases / metabolism
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DNA Methylation
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism
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Dosage Compensation, Genetic*
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Embryo Implantation
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Embryo, Mammalian / physiology*
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Epigenesis, Genetic
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Female
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Gene Expression Regulation
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Gene Expression Regulation, Developmental*
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Male
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Methyl-CpG-Binding Protein 2
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Mice
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Mice, Inbred C57BL
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Nuclear Transfer Techniques*
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Polycomb-Group Proteins
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Promoter Regions, Genetic
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism
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RNA, Long Noncoding
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RNA, Untranslated / genetics
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RNA, Untranslated / metabolism
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Repressor Proteins / genetics
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Repressor Proteins / metabolism
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X Chromosome / genetics*
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X Chromosome / metabolism*
Substances
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Biomarkers
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Chromosomal Proteins, Non-Histone
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DNA-Binding Proteins
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Mecp2 protein, mouse
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Methyl-CpG-Binding Protein 2
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Polycomb-Group Proteins
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RNA, Long Noncoding
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RNA, Untranslated
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Repressor Proteins
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XIST non-coding RNA
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Protein Serine-Threonine Kinases
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Cyclin-Dependent Kinases
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PCTAIRE-1 protein kinase