Gene screen hints at what makes stem cells special.
Two teams have found the genes that distinguish stem cells from ordinary cells1,2. The list might help scientists find new types of stem cell, and coax them to grow into replacement tissues and organs.
It might also resolve arguments about the merits of different types of stem cell. "People who want to battle out which stem cell can do what, can do so by manipulating some of these genes," says developmental biologist Miguel Ramalho-Santos of Harvard University in Cambridge, Massachusetts.
About 200 genes are at least two to three times more active in mouse stem cells than in mature brain or blood cells, the studies found. The researchers looked at embryonic stem cells, which can give rise to all types of cell, and adult nerve and blood stem cells, which are dedicated to repairing specific tissues.
"Researchers who want to find heart, bone or muscle stem cells can now go looking with a sort of check-list," says Douglas Melton, who led the Harvard team. His lab is hunting for stem cells in the pancreas.
The data will be "a tremendous boon for science and medicine", says cell biologist Helen Blau of Stanford University in Palo Alto, California.
The two groups copied the cells' active genes and swirled them onto microchips bearing copies of nearly every mouse gene. Active genes in stem cells were matched to DNA on the chip, allowing the researchers to identify them.
About half of the genes that are more active in stem cells are involved in communication between cells, copying DNA and responses to stress. What the rest do is unknown.
“This is a tremendous boon for science and medicine Helen Blau , Stanford University”
Blood stem cells in mice and humans have 322 active genes in common, according to the second group, led by molecular biologist Ihor Lemischka of Princeton University, New Jersey.
Adult stem cells are poorly understood - claims that some can form many types of tissue are still controversial. Researchers also argue about the differences between embryonic and adult stem cells.
Such disagreements are premature until we know more, says Lemischka. "There's no justification at this point for saying one type of stem cell is best."
The gene list could be used to verify the 'stemness' of proposed stem cells, says Melton. It may also explain what triggers adult stem cells to repair damaged tissue.
Ivanova, N. et al. A stem cell molecular signature. Science, 10.1126/science.1073823, (2002).
Ramalho-Santos, M. et al. "Stemness": Transcriptional profiling of embryonic and adult stem cells. Science, 10.1126/science.1072530, (2002).