Researchers have now shown how a trio of proteins controls whether an embryonic stem cell takes an irreversible step toward developing into specific tissues or retains its raw potential to become a blood cell, bone cell, brain cell, or any other kind of cell.
Stem cells' unique capacity to develop into any type of cell—a property known as pluripotency—underlies their medical promise. Researchers argue that this trait could someday lead, for example, to lab-grown tissue and organs that would be useful for transplants.
The scientists set out to determine what genes define a stem cell. "We thought if we could uncover this network of genes, then we could see how pluripotency is established," says Laurie A. Boyer of the Whitehead Institute in Cambridge, Mass. And with knowledge of the mechanics behind pluripotency, she says, scientists might learn to reprogram a mature cell so that it, too, could have the pluripotency of a stem cell.