Nuclear reprogramming of cloned embryos produced in vitro

Despite the fact that cloned animals derived from somatic cells have been successfully generated in a variety of mammalian species, there are still many unsolved problems with current cloning technology. Somatic cell nuclear transfer has shown several developmental aberrancies, including a high rate...

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Bibliographic Details
Published in:Theriogenology 2003, Vol.59 (1), p.33-44
Main Authors: Han, Y.M, Kang, Y.K, Koo, D.B, Lee, K.K
Format: Article
Language:English
Subjects:
Animals
Cattle
Cell Nucleus - chemistry
Cloning, Organism
Congenital Abnormalities
DNA Methylation
Embryo
Embryonic and Fetal Development
Gene Expression Regulation, Developmental
Genetic Engineering
Nuclear Transfer Techniques
Reprogramming
Somatic cell nuclear transfer
Swine - embryology
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Summary:Despite the fact that cloned animals derived from somatic cells have been successfully generated in a variety of mammalian species, there are still many unsolved problems with current cloning technology. Somatic cell nuclear transfer has shown several developmental aberrancies, including a high rate of abortion during early gestation and increased perinatal death. One cause of these developmental failures of cloned embryos may reside in the epigenetic reprogramming of somatic donor genome. In mammals, DNA methylation is an essential process in the regulation of transcription during embryonic development and is generally associated with gene silencing. A genome-wide demethylation may be a prerequisite for the formation of pluripotent stem cells that are important for later development. We analyzed methylation patterns in cloned bovine embryos to monitor the epigenetic reprogramming process of donor genomic DNA. Aberrant methylation profiles of cloned bovine embryos were observed in various genomic regions, except in single-copy gene sequences. The overall genomic methylation status of cloned embryos was quite different from that of normal embryos produced in vitro or in vivo. These results suggest that the developmental failures of cloned embryos may be due to incomplete epigenetic reprogramming of donor genomic DNA. We expect that advances in understanding the molecular events for reprogramming of donor genome will contribute to clarify the developmental defects of cloned embryos.
ISSN:0093-691X
1879-3231
DOI:10.1016/S0093-691X(02)01271-2