The researchers of the National Institute on Aging (NIA), which forms part of the National Institutes of Health, have found out a solution to embryonic stem (ES) cell restoration in a gene, known as the Zscan4, like it was reported in the online issue of Nature on the 24th of March 2010.
This breakthrough discovery could have serious implications for research concerning aging, regenerative medicine, stem cell biology as well as cancer biology. ES cells are one of a kind as, along with the capability to develop into almost any kind of cell in the human body, they can moreover produce an infinite cohort of new ES cells (daughter cells) that are fully operational. ES cells are fundamentally immortal, that is, they can indefinitely divide in order to produce supplementary generations of operational ES daughter cells. The majority of other cells have the ability to produce only a limited number of generations of daughter cells before these cells no longer function effectively. The reason for this is part because the telomere – the protective end of chromosomes that carries the cell’s genetic information – becomes shorter with time as the cell divides. A telomere is unable to protect the cell when it becomes too short. When this happens, the cells dies, it turns itself off, called the cell senescence or start to produce abnormal or even dysfunctional cells.
Till now, the mechanism regarding the immortality of the ES cell had remained a secret. The theory that had been prevailing was that the ES cell engaged in “self-renewal”, that is, when the cells divided, they also produced daughter cells that were totally unchanged (including telomere length) from the parent cell.
The NIA researchers found out that the process that takes place in ES cells can be better described as “rejuvenation” instead of “self-renewal”. Because in other cells, when there is replication of the ES cells, the daughter cells are not the same as their parent cell and their telomeres are shorter. On the other hand, the ES cell expresses a unique gene – Zscan4. When this gene is activated, the ES cell is rejuvenated thus restored to its initial vigor. This process of rejuvenation comprises of the lengthening of the telomere, through recombination, meaning that when a shorter telomere combines itself with a longer telomere, it results in elongating itself. It should be noted that the gene is not activated each time that the cell reproduces- nearly 5 percent of the cells will have a gene that is turned on at any one point of time. The process consists of a cell replication cycle – involving the shortening of the telomere- and an altering activation of the Zscan4.
Researchers are actually investigating the possibility of having similar mechanism that operates in the human cells as well.
Source: NIA and E-sciencenews
Sun, Jun 20, 2010
Bioscience, Stem cells