Neurogenesis is the process by which nervous system cells, also known as neurons, are produced by neural stem cells. Neural stem cells are cells that have the potential to produce many different types of nervous system cells. They include neuroepithelial (NEP) stem cells, radial glial cells (RGCs), basal progenitors (BPs), subventricular zone astrocytes, and subgranular zone radial astrocytes, among others. Neurogenesis is most abundant during embryonic development, when a child is still in the womb, but it continues throughout adult life.
Neurogenesis begins during embryogenesis in all animals and is responsible for producing all the neurons of the organism.[1] Prior to the period of neurogenesis, neural stem cells first multiply. The primary neural stem cell of the mammalian brain, called a radial glial cell, resides in an embryonic zone called the ventricular zone, which lies adjacent to the developing brain ventricles.[2][3] The process of neurogenesis then involves a final cell division of the parent neural stem cell, which produces daughter neurons that will never divide again. Most neurons of the human central nervous system live the lifetime of the individual. The molecular and genetic factors influencing neurogenesis notably include the Notch pathway, and many genes have been linked to Notch pathway regulation.[4][5] In mammals, adult neurogenesis has been shown to occur in two primary regions in the brain: the dentate gyrus of the hippocampus and the subventricular zone (SVZ). In some mammals, such as rodents, the olfactory bulb is a zone which features integration of adult-born neurons, which migrate from the SVZ through the rostral migratory stream (RMS).[6] In some vertebrates, regenerative neurogenesis has also been shown to occur.[7] Many environmental factors, such as exercise, stress, and antidepressants, have been shown to change the rate of neurogenesis within the hippocampus.[8][9]
Contents
- 1 Prenatal Neurogenesis
- 2 Postnatal Neurogenesis
- 3 See also
- 4 References
- 5 External links
Prenatal Neurogenesis
Neurogenesis during embryonic development takes place in three stages[10]. First, neuroepithelial stem cells produce neurons in the neural tube, which will later become the brain and spinal cord. After the neural tube closes, neural stem cells operate in the ventricular zone, and radial glial cells replace neuroepithelial cells as the primary producers of new neurons. As embryonic development draws to a close, the ventricular zone finishes developing into the ventricular system of the brain, where the cerebrospinal fluid (CSF) that surrounds and protects the brain is produced. Neural stem cells called basal progenitors form the tissue that makes up the subventricular zone (SVZ). After embryonic brain development, neural stem cells reside primarily in the subventricular zone and in another area called the subgranular zone (SGZ) of the dentate gyrus of the hippocampus, and will continue to do so during adulthood.
Postnatal Neurogenesis
Postnatally, neurogenesis occurs in response to signals coming from either inside or outside of the body instead of occurring automatically as it does in prenatal development[10]. The primary neural stem cells in adulthood are subventricular zone astrocytes and subgranular zone radial astrocytes rather than radial glial cells. Most of these adult neural stem cells lie dormant in the subventricular zone or the subgranular zone. In response to signals, dormant cells, or B cells, produce proliferating cells, or C cells. The C cells then produce the neuroblasts, or A cells, that will become neurons.
Adult neurogenesis often serves one of a small number of purposes. For example, neuroblasts might travel via the Rostral Migratory Stream (RMS) to the olfactory bulb, the region containing cells that detect smell. The neuroblasts in the olfactory bulb become interneurons that help the brain communicate with these sensory cells. The majority of those interneurons are inhibitory granule cells, but a small number are periglomerular cells. Neuroblasts might also migrate to the hippocampus and mature into dentate granule cells.
Significant neurogenesis also occurs after birth in the hippocampus. The hippocampus plays a crucial role in the formation of new declarative memories, and it has been theorized that the reason infants cannot form declarative memories because they are still undergoing extensive neurogenesis in the hippocampus.[11] Previous cognitive research suggested that infants could not form declarative memories because of their lack of language skills, but the fact that analogs to this “infantile amnesia” can be observed in non-human mammals indicates that a lack of language does not account for the entire phenomenon. Significant neurogenesis also occurs in the hippocampus just after birth, and much of adult neurogenesis occurs in the dentate gyrus of the hippocampus as well.
See also
- Adult neurogenesis
- Cellular differentiation
- Gliogenesis
- Noogenesis
References
- ^ Eric R. Kandel, ed. (2006). Principles of neural science (5. ed.). Appleton and Lange: McGraw Hill. ISBN 978-0071390118.
- ^ Rakic, P (October 2009). "Evolution of the neocortex: a perspective from developmental biology". Nature Reviews. Neuroscience. 10 (10): 724–35. doi:10.1038/nrn2719. PMC 2913577 . PMID 19763105.
- ^ Lui, JH; Hansen, DV; Kriegstein, AR (8 July 2011). "Development and evolution of the human neocortex". Cell. 146 (1): 18–36. doi:10.1016/j.cell.2011.06.030. PMC 3610574 . PMID 21729779.
- ^ Kageyama, R; Ohtsuka, T; Shimojo, H; Imayoshi, I (November 2008). "Dynamic Notch signaling in neural progenitor cells and a revised view of lateral inhibition". Nature Neuroscience. 11 (11): 1247–51. doi:10.1038/nn.2208. PMID 18956012.
- ^ Rash, BG; Lim, HD; Breunig, JJ; Vaccarino, FM (26 October 2011). "FGF signaling expands embryonic cortical surface area by regulating Notch-dependent neurogenesis". The Journal of Neuroscience. 31 (43): 15604–17. doi:10.1523/jneurosci.4439-11.2011. PMC 3235689 . PMID 22031906.
- ^ Ming, GL; Song, H (May 26, 2011). "Adult neurogenesis in the mammalian brain: significant answers and significant questions". Neuron. 70 (4): 687–702. doi:10.1016/j.neuron.2011.05.001. PMC 3106107 . PMID 21609825.
- ^ Alunni, A; Bally-Cuif, L (1 March 2016). "A comparative view of regenerative neurogenesis in vertebrates". Development. 143 (5): 741–753. doi:10.1242/dev.122796. PMC 4813331 . PMID 26932669.
- ^ Hanson, Nicola D.; Owens, Michael J.; Nemeroff, Charles B. (2011-12-01). "Depression, Antidepressants, and Neurogenesis: A Critical Reappraisal". Neuropsychopharmacology. 36 (13): 2589–2602. doi:10.1038/npp.2011.220. ISSN 0893-133X. PMC 3230505 . PMID 21937982.
- ^ Santarelli, Luca; Saxe, Michael; Gross, Cornelius; Surget, Alexandre; Battaglia, Fortunato; Dulawa, Stephanie; Weisstaub, Noelia; Lee, James; Duman, Ronald (2003-08-08). "Requirement of Hippocampal Neurogenesis for the Behavioral Effects of Antidepressants". Science. 301 (5634): 805–809. doi:10.1126/science.1083328. ISSN 0036-8075. PMID 12907793.
- ^ a b Jin, Xing (2016-09-01). "The role of neurogenesis during development and in the adult brain". European Journal of Neuroscience. 44 (6): 2291–2299. doi:10.1111/ejn.13251. ISSN 1460-9568.
- ^ Josselyn, Sheena A.; Frankland, Paul W. (2012-09-01). "Infantile amnesia: A neurogenic hypothesis". Learning & Memory. 19 (9): 423–433. doi:10.1101/lm.021311.110. ISSN 1072-0502. PMID 22904373.
External links
- http://sites.lafayette.edu/neur401-sp10/what-is-neurogenesis/a-timeline-of-research-adult-mammalian-neurogenesis/
- http://thebrain.mcgill.ca/flash/capsules/histoire_bleu05.html
- Article: Nature Medicine 4, 1313 - 1317 (1998) doi:10.1038/3305 Neurogenesis in the adult human hippocampus
