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© The Rockefeller University Press, 0021-9525/2003/7/10 $5.00
The Journal of Cell Biology, Volume 162, Number 1, 10-10

Histones help clones forget their pasts

Histone acetylation (left) goes away during meiosis (right) and nuclear transfer.

Amid the hype surrounding cloning by somatic cell nuclear transfer, the astonishingly low success rate of the process has received relatively little attention. Now, on page 37, Kim et al. show that histone deacetylation is an important feature of the nuclear reprogramming that occurs in oocytes, both during normal meiosis and in nuclear transfer experiments. The work suggests strategies that could improve the efficiency of cloning, and also helps to explain how somatic cells retain their identities during mitosis.

Using immunocytochemistry, the authors examined changes in histone acetylation in oocytes during meiosis, and compared these with mitotic acetylation patterns. In meiotic oocytes, histone acetylation levels drop markedly. A similar decrease occurs in somatic cell nuclei that are transferred into enucleated oocytes. During mitosis, however, the same sites on histones remain acetylated. The histone deacetylase enzyme HDAC1 colocalizes with chromosomes during meiosis, but not during mitosis.

Kim et al. suggest that the acetylation states of histones propagate "cell memory," ensuring that cells retain information about their lineages during mitosis. In meiotic oocytes or transferred somatic cell nuclei, histone deacetylases gain access to the chromosomes, erasing cell memory and reprogramming the nucleus so that it can give rise to all of the cell types in a new embryo.

Currently, the only way to determine whether a transferred somatic cell nucleus has been reprogrammed in a cloning experiment is to implant the oocyte and wait for the embryo to develop. The new work suggests that an assay of histone acetylation levels might sort the reprogrammed nuclei from the failures, potentially increasing the efficiency of cloning. Reagents that increase deacetylation or target histone deacetylases to the chromosomes might also make the process more reliable. The authors are now trying to identify the molecular mechanisms that regulate the localization of histone deacetylases during meiosis.

Alan W. Dove

alanwdove{at}earthlink.net

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Jin-Moon Kim, Honglin Liu, Mayuko Tazaki, Masao Nagata, and Fugaku Aoki
J. Cell Biol. 2003 162: 37-46. [Abstract] [Full Text] [PDF]

This Article Full Text (PDF, 771K) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Dove, A. W. Search for Related Content PubMed Articles by Dove, A. W. Related Collections Related Article Social Bookmarking                            What's this?