Characterization of the subventricular zone of the adult human brain: evidence for the involvement of Bcl-2

The subventricular zone (SVZ) is an embryonic remnant that persists and remains mitotically active throughout adulthood. The rodent SVZ harbors neuronal precursors, principally in its anterior part, and generates neuroblasts that migrate tangentially into the olfactory bulb, thus forming the so-called rostral migratory stream. This study aimed at characterizing the SVZ in the human brain. Antibodies raised against the widely used SVZ molecular markers nestin, glial fibrillary acidic protein, beta-tubulin-III and polysialylated neural cell adhesion molecule, have allowed us to characterize in detail a zone similar to the rodent SVZ in humans. Virtually all portions of the lateral ventricle, as well as the ventral (hypothalamic) sector of the third ventricle, displayed immunoreactivity for most of the molecular markers. The midline region of the septum (septal recess) and the ventral portion of the SVZ displayed a particularly intense immunostaining for all SVZ markers. These two regions may represent zones of adult neurogenesis that are unique to primates. Furthermore, the anti-apoptotic protein Bcl-2 was found to be actively synthesized and co-expressed with all the other markers throughout the entire SVZ. This study reveals that a well-developed SVZ exists in the adult human brain and suggests that Bcl-2 might play an important role in the functional organization of such a system.