Genes Key to Stem
Cells' "Stemness" Identified
September13, 2002; New York, NY ( Reuters Health) In findings that could lead to a better understanding of how stem cells work as well as help scientists to identify new types of stem cells, two sets of researchers have identified sets of genes that are shared by several types of stem cells. Stem cells are immature "master" cells capable of maturing into different types of body tissue. These cells are most abundant in embryos, but there are also stem cells in some adult tissues, such as bone marrow.
Despite great interest in using stem cells to treat disease, very little is known about the genetics of the cells. To find out more, Dr. Douglas A. Melton of the Howard Hughes Medical Institute and Harvard University in Cambridge, MA and colleagues "profiled" the genes of several types of mouse stem cells. They selected the three varieties of stem cells that have been studied the most: (1) embryonic stem cells; (2) neural stem cells; and (3) hematopoietic cells, which give rise to blood cells.
Melton's team identified 216 genes that were expressed, or "turned on," in high levels in all three types of stem cells. According to a report the September 12th issue of Sciencexpress, the online edition of the journal Science, this set of genes is "likely to reveal core stem cell properties or 'stemness'" that give stem cells their special properties, including self-renewal.
"The study shows that a set of genes, not one gene, but a set of about 200 genes, gives stem cells their special properties," Melton told Reuters Health. He said that the genes identified in the study "are likely to be important for an organism's ability to maintain itself (and) regenerate tissues."
According to Melton, the newly identified genes "should help scientists identify and purify stem cells from other tissues." Pointing out that the study involved blood, brain and embryonic stem cells, he said that the new information can now be used to find stem cells in the pancreas, bone, heart, and other tissues.
The results of a second study, also published in Sciencexpress, suggest that the genetic similarity of stem cells applies to human cells as well. When a group of researchers at Princeton University in NJ compared mouse and human hematopoietic stem cells, they found that the cells expressed a number of the same genes. The similarities between the mouse and human stem cells, according to the researchers, may represent a "molecular signature" that governs the properties shared by various types of stem cells. The team also found that mouse hematopoietic stem cells shared some of the same molecular signature as mouse embryonic and neural stem cells.
In an interview with Reuters Health, the study's lead author, Dr. Ihor R. Lemischka, compared the molecular signature to a "parts list." As is the case with a computer or any other machine, "you need to know what the parts are," he said. Now that researchers have identified the components of several types of stem cells, he said, the next step is to figure out "how they fit together."
ImClone Systems Inc. provided some funding for the Princeton study.
SOURCE: Sciencexpress 2002;10.1126/science.1072530, 1073823.