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via Gene Targeting To explain mouse embryonic stem cell immortality revealed by the study in zebrafish

Researchers at the National Institute on Aging (NIA), part of the National Institutes of Health, have discovered a key to embryonic stem (ES) cell rejuvenation in a gene - Zscan4 - as reported in the edition of March 24, 2010, online in Nature. This finding could advance tener implicaciones importantes para la investigación del envejecimiento, biología de células madre, la medicina regenerativa y la biología del cáncer.

células madre embrionarias son únicas porque, junto con la capacidad de convertirse en casi cualquier tipo de célula en el cuerpo, pueden producir infinidad de generaciones nuevas, las células ES en pleno funcionamiento (células hijas). células madre embrionarias son esencialmente inmortal, es decir que pueden dividirse indefinidamente para producir generaciones funcionales adicionales de las células ES daughters. Other cells can only produce a certain number of generations of daughter cells before they no longer work correctly. This is partly because the telomere, in order to protect the chromosome that carries genetic information in cells is shortened each time a cell divides. When telomeres become very short, can no longer protect the cell. At that time, the cell dies, it turns itself off, known as cellular senescence, or produce abnormal and dysfunctional cells, possibly.

So far, the mechanism for ES cell immortality had been a mystery. The prevailing theory was that ES cells practice "self-renewal, which means that when it divides, daughter cells are produced that were completely natural (including the length of telomeres) parent. NIA researchers found that the process that occurs in embryonic stem cells may be more properly described as "rejuvenating" the "self-renewal." As in other cells when the ES cells replicate, the daughter cells are not identical to the parents and the telomeres are shorter.

However, ES cells express a gene Zscan4 only, when activated (or on), ES cells rejuvenate, restore its original force. This rejuvenation includes telomere elongation through recombination, the shorter telomeres when combined with a telomere itself more time to elongated. Zscan4 then turns off. The gene is not activated each time the cell replicates - about 5 percent of the cells have a gene turned on at any point. The process is a cycle of cell replication (with telomere shortening) and intermittent activation Zscan4 (rejuvenation of cells).