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Perspectives
Maintenance of Epigenetic Memory in Cloned Embryos
Ray K. Ng and J. B. Gurdon
volume 4 | issue 6
june 2005Pages: 760-763
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Different cell types have characteristic patterns of gene expression. Once a cell has differentiated, its daughter cells nearly always differentiate in the same way. The maintenance of cell lineage involves either instructions from a cell’s surroundings or the inheritance of memory from a parent cell. In normal development, the differentiation state of a cell is remarkably stable and irreversible. However the transplantation of a somatic cell nucleus to an enucleated egg often leads to a complete reprogramming of gene expression. We summarize here the results of some Amphibian nuclear transfer experiments that reveal a memory of gene expression. This and some other experiments exemplify epigenetic memory that persists through many cell divisions. In the case of nuclear transfer experiments, the actively transcribed state of a gene can be propagated through many cell divisions in the absence of the stimulus that first induced the activity of this gene. We discuss the possible basis of these two examples of persistent epigenetic memory, namely changes at DNA methylation, and histone modifications.
We now provide open access to journal articles published online for one year or more. This article may be downloaded at the following link:
Download PDF If the document does not open, please right-click on the link (control-click on a Macintosh) and select the option to save the file to disk.