Stem Cell Maintenance Protein Wnt Isolated.

Scientists have finally isolated the first member of a recalcitrant group of proteins called the Wnts- two decades after their discovery. These proteins were suspected to have a role in keeping stem cells in their youthful, undifferentiated state-a suspicion that has proven correct, according to research carried out in two laboratories at Stanford University Medical Center (Stanford, CA 94305; Tel: 650/723-2300; Website: www.stanford.edu). The ability to isolate Wnt proteins could help researchers grow some types of stem cells for use in bone marrow transplants or other therapies.

The gene coding for a protein usually reveals clues about how that protein will react in the lab and how best to isolate it from other molecules. The Wnts are unusual, however, because the way they behave in the lab differs from what the gene suggests. Roeland Nusse, professor of developmental biology at the School of Medicine and one of the first to isolate a Wnt gene, reports how his lab members overcame these hurdles in the April 27 online edition of the journal Nature.

"We found that the protein is modified, explaining why it has been difficult to isolate," says Nusse, who is also an investigator at the Howard Hughes Medical Institute. Although the protein's structure suggests that it should be water soluble, Karl Willert, a postdoctoral fellow in Nusse's lab, found that an attached fat molecule makes the protein shun water and prefer the company of detergents instead.

With a Wnt in hand, researchers could finally confirm previous hints that the protein helps stem cells maintain their youthful state. This work, led by Irving Weissman, involved cells in the bone marrow called hematopoietic stem cells that generate blood cells throughout a person's life. When these cells divide, some offspring go on to become red blood cells, immune cells, and other blood components, while other offspring continue the stem cell line.

Experiments carried out by Tannishtha Reya, a ...