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Unfaithful Maintenance of Methylation Imprints Due to Loss of Maternal Nuclear Dnmt1 during Somatic Cell Nuclear Transfer

By Yanchang Wei, Yanjun Huan, Yongqian Shi, Zhongfeng Liu, Gerelchimeg Bou, Yibo Luo, Li Zhang, Cairong Yang, Qingran Kong, Jiangtian Tian, Ping Xia, Qing-Yuan Sun and ZhongHua Liu


The low success rate of somatic cell nuclear transfer (SCNT) in mammalian cloning is largely due to imprinting problems. However, little is known about the mechanisms of reprogramming imprinted genes during SCNT. Parental origin-specific DNA methylation regulates the monoallelic expression of imprinted genes. In natural fertilization, methylation imprints are established in the parental germline and maintained throughout embryonic development. However, it is unclear whether methylation imprints are protected from global changes of DNA methylation in cloned preimplantation embryos. Here, we demonstrate that cloned porcine preimplantation embryos exhibit demethylation at differentially methylated regions (DMRs) of imprinted genes; in particular, demethylation occurs during the first two cell cycles. By RNAi-mediated knockdown, we found that Dnmt1 is required for the maintenance of methylation imprints in porcine preimplantation embryos. However, no clear signals were detected in the nuclei of oocytes and preimplantation embryos by immunofluorescence. Thus, Dnmt1 is present at very low levels in the nuclei of porcine oocytes and preimplantation embryos and maintains methylation imprints. We further showed that methylation imprints were rescued in nonenucleated metaphase II (MII) oocytes. Our results indicate that loss of Dnmt1 in the maternal nucleus during SCNT significantly contributes to the unfaithful maintenance of methylation imprints in cloned embryos

Topics: Research Article
Publisher: Public Library of Science
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Provided by: PubMed Central

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  15. (1997). DNA methyltransferases in mouse tissues and cells. Studies with a mechanism-based probe.
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  17. (1998). Eight calves cloned from somatic cells of a single adult.
  18. (2005). Expression of imprinted genes is aberrant in deceased newborn cloned calves and relatively normal in surviving adult clones.
  19. (2002). Faithful expression of imprinted genes in cloned mice.
  20. Ferguson-Smith AC (2007) Mechanisms regulating imprinted genes in clusters.
  21. (1998). Full-term development of mice from enucleated oocytes injected with cumulus cell nuclei.
  22. (2001). Genomic imprinting disrupted by a maternal effect mutation in the Dnmt1 gene.
  23. (2001). Genomic imprinting: Parental influence on the genome.
  24. (2001). Imprinting and the epigenetic asymmetry between parental genomes.
  25. (1998). Large offspring syndrome in cattle and sheep.
  26. (2008). Maintenance of genomic methylation patterns during preimplantation development requires the somatic form of DNA methyltransferase I.
  27. (1999). Mammalian (cytosine-5) methyltransferases cause genomic DNA methylation and lethality in Drosophila.
  28. (2008). Maternal and zygotic Dnmt1 are necessary and sufficient for the maintenance of DNA methylation imprints during preimplantation development.
  29. (2009). Methylation status of differentially methylated regions at Igf2/H19 locus in porcine gametes and preimplantation embryos.
  30. (2008). Methylation status of putative differentially methylated regions of porcine IGF2 and H19.
  31. (2007). Nuclear reprogramming of cloned embryos and its implications for therapeutic cloning.
  32. (2000). Pig cloning by microinjection of fetal fibroblast nuclei.
  33. (2008). Preimplantation expression of the somatic form of Dnmt1 suggests a role in the inheritance of genomic imprints.
  34. (1999). Production of goats by somatic cell nuclear transfer.
  35. (2003). Reprogramming of primordial germ cells begins before migration into the genital ridge, making these cells inadequate donors for reproductive cloning.
  36. (1993). Role for DNA methylation in genomic imprinting.
  37. (2009). Transgene expression is associated with copy number and cytomegalovirus promoter methylation in transgenic pigs.
  38. (1997). Viable offspring derived from fetal and adult mammalian cells.
  39. (2005). X chromosome reactivation and regulation in cloned embryos.
  40. (2000). X-Chromosome inactivation in cloned mouse embryos.