http://dailynews.yahoo.com/h/nm/20010831/sc/stemcell_research_gene_dc_1.html

Friday August 31 5:29 PM ET
By Toni Clarke

NEW YORK (Reuters) - Scientists at St. Jude Children's Research Hospital have discovered a gene that may prevent stem cells from taking on the characteristics of specific tissue, something that reduces their value as potential disease fighters.

The gene, ABCG2/Bcrp1, also appears to act as a marker that could help researchers pick out the desirable stem cells from other cells. Stem cells are primordial cells that have yet to take on the identity of a specific cell type -- such as heart or liver. Scientists believe stem cells can be manipulated to become specific tissue, which could be used to treat diseases.

The discovery, published in the September issue of Nature Medicine, could be a boon to scientists attempting to cultivate stem cell lines, or colonies. Most stem cell lines are fragile and require a good deal of maintenance. This gene could help scientists pick out the most robust cells.

"This is the beginning of an important part of the stem cell story," said Brian Sorrentino, director of experimental hematology at St. Jude and leader of the investigative team. "The mechanism by which stem cells stay primitive is one of the key questions in stem cell research."

One of the problems researchers have encountered in attempting to develop stem cell lines is the tendency for some cells to start spontaneously differentiating; that is, they start to take on the qualities of a particular type of cell. Once that happens, they lose their value as cells capable of becoming any type of cell.

Sorrentino's team found that cells expressing the ABCG2/Bcrp1 gene were the most likely to remain undifferentiated, and therefore most likely to reproduce and multiply. In cells that had become specific, the gene was not present.

"The idea here is that primitive cells express this gene but as they differentiate it is shut off," Sorrentino said. "We think this discovery could be very valuable in telling us how these decisions are made."

Scientists have long been looking for an accurate way to identify stem cells. In a sample of 100,000 bone marrow cells, only one or two may be stem cells. Those few cells are responsible in the body for replenishing cells in a particular organ as they die.

"People have looked at a variety of other markers, but nobody has ever found an absolutely specific stem cell marker," Sorrentino said. "Our work suggests that ABCG2/Bcrp1 could be that type of marker."
 

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