Epigenetic reprogramming in cloned embryos In 1997, the news from Scotland made headlines throughout the world. Dr. Ian Wilmut and his colleagues reported that they succeeded to make a live cloned offspring of sheep from cultured mammary gland cells by nuclear transfer into enucleated oocyte.
The paper we are going to discuss is one of the key papers that showed critical roles of the reprogramming of genome-wide methylation in early embryos. The authors found that genome-wide reprogramming is conserved widely throughout mammalian species. Observations in normal embryos showed active demethylation of the paternal genome at the preimplantation stage, followed by de novo methylation. In contrast, demethylation and methylation profiles in cloned embryos were abnormal at the preimplantation stage, raising a possibility that altered methylation pattern in cloned embryos could be a cause of aberrant development. Although the results presented in this paper are very important, I found many questions after reading the paper. The authors could add many additional ways to convince the readers to accept the points they claimed. In this class I would like to discuss such points with you.
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