The Yin and Yang of stem cell quiescence and proliferation

Not all adult stem cells are created equal. Some are busy regenerating worn out or damaged tissues, while their quieter brethren serve as a strategic back-up crew that steps in only when demand shoots up. In a recent study, Stowers Investigator Linheng Li, PhD, and his team identified an important molecular cue that keeps quiescent mouse hematopoietic (or blood-forming) stem cells from proliferating when their services are not needed.

Ryohichi Sugimura, a graduate student in Li’s lab, and his colleagues were able to show that Flamingo and Frizzled 8, a tag team best known for its role in establishing cell polarity, work together to maintain a quiescent reserve pool of hematopoietic stem cells in mouse bone marrow. Their finding adds new insight into the mechanism that controls the delicate balance between long-term maintenance of stem cells and the requirements of ongoing tissue maintenance and regeneration.

“Hematopoietic stem cells daily produce billions of blood cells via a strict hierarchy of lineage-specific progenitors,” says Li. “Identifying the molecular signals that allow hematopoietic stem cell populations to sustain this level of output over a lifetime is fundamental to understanding the development of different cell types, the nature of tumor formation and the aging process. My hope is that these insights will help scientists make meaningful progress towards new therapies for diseases of the blood.”

The study was published in the July 20, 2012, issue of Cell.