The discovery of a "scrawny" gene in fruit flies may improve researchers' ability to direct stem cell differentiation in desired ways, U.S. researchers say.

The gene -- called scrawny because of the appearance of mutant adult flies -- appears to be a key factor in keeping a variety of stem cells in their undifferentiated state, the researchers at the Carnegie Institution's Department of Embryology say in an article to be published Friday in the journal Science.

"Understanding how stem cells maintain their potency has implications both for our knowledge of basic biology and also for medical applications," the researchers say in a statement.

"Our tissues, and indeed our very lives, depend on the continuous functioning of stem cells," embryology director Allan Spradling says.

"Yet we know little about the genes and molecular pathways that keep stem cells from turning into regular tissue cells -- a process known as differentiation," he says.

The study found that by controlling the proteins that wrap the genes, scrawny genes can silence other genes that would otherwise cause a generalized cell to differentiate into a specific type of cell, such as a skin or intestinal cell.

While the scrawny gene has so far only been identified in fruit flies, very similar genes that may carry out the same function are known to be present in all multicellular organisms, including humans, the researchers say.

"This new understanding of the role played by scrawny may make it easier to expand stem cell populations in culture, and to direct stem cell differentiation in desired directions," Spradling says.