Embryonic stem cells are fundamental to the normal development of all tissues and organs in the body. They are unique because they can divide to produce identical copies of themselves and, under certain conditions, can differentiate into other types of cell in the body. A central goal in stem cell research is to understand how this choice between self-renewal and differentiation is determined so that one day stem cells may be used to generate new tissues for damaged or diseased organs. Until now, very little was known about the molecular mechanisms that determine stem cell behavior. This new finding establishes a fundamental role for Nanog in controlling embryonic stem cell identity. Another gene called Oct4 apparently also plays a significant role.

Reprogramming ordinary adult cells to become safe and usable embryonic stem cells is still a long way off. “That’s an aspiration and something we are keen to investigate, but it’s not going to be simple,” says fellow researcher Austin Smith of the Edinburgh Institute for Stem Cell Research. Still, such a development could end the controversial practice of harvesting embryonic stem cells from human fetuses, often cast-offs from fertility clinics.