A human embryonic stem cell is reined in prevented from giving up its unique characteristics of self-renewal and pluripotency by the presence of a protein modification that stifles any genes that would prematurely instruct the cell to develop into heart or other specialized tissue. But, thanks to the simultaneous presence of different protein modifications, stem cells are primed and poised, ready to develop into specialized body tissue, Singapore scientists reported in last months issue of the journal Cell Stem Cell.
The molecules central to this balancing act, H3K4me3 and H3K27me3, are among the so-called epigenetic modifications that influence the activity patterns of genes in both human embryonic stem (ES) cells and mature human adult cells.
Determining how ES cell genes are modified by these epigenetic markers may explain these cells unique characteristics, said the scientists, who are based at the Genome Institute of Singapore (GIS) and the Bioprocessing Technology Institute (BTI), both under the Agency for Science, Technology and Research (A*STAR), as well as at the National University of Singapore (NUS).
The scientists also discovered that genes modified only by one of the epigenetic markers, H3K4me3, contain the DNA recipes for proteins that enable an ES cell to proliferate, or duplicate itself. In the Cell Stem Cell paper, the scientists wrote, The prevalence of these genes may be related to the self-renewal property of ES cells.
The scientists also found that the genes that do not carry either of the two epigenetic modifications are completely silenced in ES cells. These genes, which are crucial to sensory processes, immunity, and drug metabolism, are active in highly specialized, mature adult cells.
Although epigenetic markers attach themselves to the tightly wound bundle of protein material called histones that package and compress the DNA in the nucleus of each human cell, they do not change the cells
|Contact: Cathy Yarbrough|
Agency for Science, Technology and Research (A*STAR), Singapore