Arturo Alvarez-Buylla and Erica L. Jackson, of the University of California, San Francisco, and colleagues reported their findings in a paper in the July 20, 2006, Neuron, published by Cell Press. In their studies, they sought to discover whether neural stem cells in the brain called B cells carry a receptor--known as platelet-derived growth factor receptor á (PDGFRá)--for the signaling molecule PDGF.
Neural stem cells are immature cells that serve as the continual source of new brain cells in adults, and PDGF is known as an important regulator of such cells. Also, PDGF has been implicated as a key signaling molecule underlying the formation of brain tumors. PDGF triggers such cell response by plugging into the target receptor on the stem cell, like a key inserting into a lock.
There had been indirect evidence that neural stem cells give rise to brain tumors. "However, it has not been shown in vivo that tumor stem cells are derived from normal stem cells or that a specific population of cells with demonstrated stem cell properties is capable of initiating tumor formation," wrote the researchers.
Using tracers, the researchers discovered that PDGFRá is, indeed, found on the stem cells in both mouse and human brain tissue. They also found that the receptor is triggered by PDGF in the stem cells to regulate their production of mature brain cells. The researchers located the PDGFRá-containing cells in the subventricular zone (SVZ) of the brain, which is the center for production of new brain cells in adults.
The researchers also found that infusing PDGF into mous