The scale could reveal if lab grown cells are equivalent to embryonic stem cells.
Scientists have proposed a simple scale of 88 genes to gauge the usefulness of stem cells.
It might help researchers to work out whether they can convert adult cells from say, blood or skin, into stem cells that are able to grow medically valuable repair tissues.
The 88 genes are a subset of the nearly 3,000 that are frequently active in young mouse embryos or stem-cell cultures, Minoru Ko of the National Institutes of Health in Bethesda, Maryland told this week's Human Genome Organisation meeting in Cancun, Mexico.
Ko's group found that changes in the activity of this subset correlates with a stem cell's ability to produce other cell types. Until now, the only way to test a stem cell's potential has been to grow it and examine its descendants.
A freshly fertilized egg that is able to produce every cell type in the body, for example, gets one score in the analysis; older cells that can make only blood, say, or nerves, receive another. "We will measure the activity of those 88 genes to tell what stage it is at," suggests Ko.
The scale might reveal whether stem cells grown in the laboratory really are equivalent to ones in particular embryonic tissues, speculates Calvin Harley of biotech company Geron Corporation in Menlo Park, California. "It's fascinating," he says.
Many researchers are trying to understand what combination of genes is switched on in embryonic stem (ES) cells, adult stem cells and heart or brain cells, for example. This might reveal ways to convert one type into another - to treat heart disease or Parkinson's disease, for example.
Ko says that his 88 genes are not necessarily the ones that can drive this conversion. They may simply be altered during the switch.
In a similar vein, Harley has homed in on ten genes that seem to characterize human ES cells. He hopes to use these to grow and label a consistent supply of ES cells for clinical trials.
Because such gene signatures might be patented, researchers admit that they are not fully cooperating in their efforts. Some are, however, making their results available in online databases.