[Where have the neuronal stem cells of the subependymal zone gone in human beings?]

Stem cells are characterized by their ability for self-renewal (allowing them to be present throughout the entire life of the organism) and their ability to give rise to differentiated cells belong to one or more lineages. The strict definition of these cells is however still a matter of debate. There is new experimental evidence (including in human beings) that stem cells are present within the brain and may give rise to neurons. Ependymal cells have been proposed to play such a role. In fact, subependymal cells expressing GFAP would be more likely candidates. Such cells are observed in the brain of human beings. They are able to differentiate into neurons in vitro but such potential appears to be repressed in vivo.