How Do They Do That?

Stem cells can become any type of cell that the body needs, but until they're needed to turn into a neural cell, or a heart cell, or a skin cell, how do they stay in their "stemmy" state, asks Not Exactly Rocket Science's Ed Yong. Answering that question, researchers at the Broad Institute found that stem cells use lincRNAs to stay in their undifferentiated state until they are needed, Yong says. There are thousands of lincRNAs and, aside from a handful of examples, not much is known about their role. "Some scientists have suggested that they're mostly genetic scrap, produced when our cells copy more useful bits of information from nearby genes," Yong says. But the Broad researchers, led by Mitchell Guttman, had a different idea. For their study, which was recently published in Nature, they knocked out the lincRNAs one at a time in the embryonic stem cells of mice, and found that around 95 percent of these lincRNAs "caused a profound shift in the activity of other genes when they disappeared," Yong says. The team also found that about 10 percent of lincRNAs are responsible for keeping stem cells in a pluripotent state. Some of them control the activity of genes that maintain the "stemmy" state, while others repress genes that would change the stem cells into more specific cells. "This discovery could help scientists to reliably convert stem cells into different tissues and organs of interest. That's a necessary step towards creating bespoke organs — a major goal of medical biology," Yong adds.