( What exactly makes a stem cell a stem c...)Researchers discover key to human embryonic stem-cell potential

Now, researchers at Whitehead Institute for Biomedical Research working with human embryonic stem cells have uncovered the process responsible for the single-most tantalizing characteristic of these cells: their ability to become just about any type of cell in the body, a trait known as pluripotency.

"This is precisely what makes these stem cells so interesting from a therapeutic perspective," says Whitehead Member Richard Young, senior author on the paper which will be published September 8 in the early online edition of the journal Cell. "They are wired so they can become almost any part of the body. We've uncovered a key part of the wiring diagram for these cells and can now see how this is accomplished."

Once an embryo is a few days old, the stem cells start to differentiate into particular tissue types, and pluripotency is forever lost. But if stem cells are extracted, researches can keep them in this pluripotent state indefinitely, preserving them as a kind of cellular blank slate. The therapeutic goal then is to take these blank slates and coax them into, say, liver or brain tissue. But in order to guide them out of pluripotency with efficiency, we need to know what keeps them there to begin with.

Researchers in the Whitehead laboratories of Young, Rudolf Jaenisch, MIT-computer scientist David Gifford, and the Harvard lab of Douglas Melton focused on three proteins known to be essential for stem cells. These proteins, Oct4, Sox2, and Nanog, are called "transcription factors," proteins whose job is to regulate gene expression. (Transcription factors are really the genome's primary movers, overseeing, coordinating, and controlling all gene activity.)

These proteins were known to play essential role
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Source:Whitehead Institute for Biomedical Research