[Neurogenesis in the adult brain].
BACKGROUND
The discovery that new neurons continue to be generated in the adult brain has modified the concept of brain plasticity and has brought to light new mechanisms that ensure the homeostasis of the nervous system.


METHODS
Neurogenesis, that is to say, the process involving the generation of new neurons, has been shown to occur in the hippocampus and in the olfactory bulb in adult mammals, which suggests that neuronal stem cells persist throughout the entire lifespan. The primary precursors have been identified in specialised regions called neurogenic niches. Interestingly, the cells that give rise to the new neurons in the adult brain express markers for glial cells, a cell lineage that is a long way from that of neurons. Studies conducted during the development of the brain have shown that radial glial cells not only give rise to astrocytes but also neurons, oligodendrocytes and ependymal cells. In addition, it is known that radial glial cells are also the precursors of neuronal stem cells in the adult brain.


CONCLUSIONS
Overall, these data support the idea that stem cells develop from a neuroepithelial-glial radial-astrocytic lineage. Thus, identifying the primary precursors, both in the developing brain and in the adult brain, is essential to understand the functioning of the nervous system and, from there, to develop strategies for neuronal replacement in the adult brain when needed.
Arias-Carrión
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O
Departamento de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510 Mexico DF, Mexico. arias@ifc.unam.mx
Olivares-Buñuelos
T
T
Drucker-Colín
R
R
D000328:Adult; D000818:Animals; D001921:Brain / Q000033:anatomy & histology / Q000254:growth & development* / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D019070:Cell Lineage; D002465:Cell Movement / Q000502:physiology; D006706:Homeostasis; D006801:Humans; D009457:Neuroglia / Q000166:cytology / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D009830:Olfactory Bulb / Q000166:cytology / Q000502:physiology; D013234:Stem Cells / Q000166:cytology / Q000502:physiology*