Locating and labeling neural stem cells in the brain.

The phenomenon of adult neurogenesis has been demonstrated in most mammals including humans. At least two regions of the adult brain maintain stem cells throughout life; the subgranular zone (SGZ) of the hippocampal dentate gyrus, and the subventricular zone (SVZ) of the lateral ventricle wall. Both regions continuously produce neurons that mature and become integrated into functional networks that are involved in learning and memory and odor discrimination, respectively. Apart from these well-studied regions neurogenesis has been reported in a number of other brain regions, such as amygdala and cortex. However, these studies have been contested and there is currently no well-postulated function for non-SVZ/SGZ neurogenesis. The studies of the regional localization of neurogenesis in the brain have been made possible due to several methods for detecting adult neurogenesis including; bromodeoxyuridine labeling (BrdU) together with markers of mature neurons, genetic labeling, by mouse transgenesis, or with the use of viral vectors. These techniques are already put to creative use and will be essential for the discovery of the nature of the adult neural stem cells. In this mini-review, we will discuss the localization of neural stem/progenitor cells in the brain and their implications as well as discussing the pro's and con's of stem cell labeling techniques.