Jan's laboratory at UCSF (Cell Volume 127, Issue 6, 15 December 2006) has looked at an area of the brain known as the subventricular zone (SVZ). They showed that a gene called Numb regulates how stem cells from the SVZ become neurons, and instructs these cells to maintain the walls of the lateral ventricles, the brain's central cavities.
With Numb knocked out, mice developed large holes in these walls. But, rather than worsening over time, the holes were repaired within 6 weeks. The team suggests that stem cells that escaped the knockout were able to shore up the walls. Such capacity for do-it-yourself repair might be harnessed to treat brain damage.