Neuronal migration

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Neuronal migration is the method by which neurons travel from their origin or birth place (i.e. the location of their last cell division) to their final position in the brain.[1] There are several ways they can do this, e.g. by radial migration or tangential migration.[2] In humans, this process is largely completed by the end of the fifth month of gestation.

Radial migration

Neuronal precursor cells proliferate in the ventricular zone of the developing neocortex. The first postmitotic cells to migrate form the preplate which are destined to become Cajal-Retzius cells and subplate neurons. These cells do so by somal translocation. Neurons migrating with this mode of locomotion are bipolar and attachs the leading edge of the process to the pia. The soma is then transported to the pial surface by nucleokinesis, a process by which a microtubule "cage" around the nucleus elongates and contracts in association with the centrosome to guide the nucleus to its final destination.[3] Radial glia, whose fibers serve as a scaffolding for migrating cells, can itself divide[4] or translocate to the cortical plate and differentiate either into astrocytes or neurons.[5] Somal translocation can occur at any time during development.[2]

Subsequent waves of neurons split the preplate by migrating along radial glial fibres to form the cortical plate. Each wave of migrating cells travel past their predecessors forming layers in an inside-out manner, meaning that the youngest neurons are the closest to the surface.[6][7] It is estimated that glial guided migration represents 90% of migrating neurons in human and about 75% in rodents.[8]

Tangential migration

Most interneurons migrate tangentially through multiple modes of migration to reach their appropriate location in the cortex. An example of tangential migration is the movement of Cajal-Retzius cells from the ganglionic eminence to the cerebral cortex. One example of ongoing tangential migration in a mature organism, observed in some animals, is the rostral migratory stream connecting subventricular zone and olfactory bulb.

Other types of neuronal migration

There is also a method of neuronal migration called multipolar migration.[9][10] This is seen in multipolar cells, which are abundantly present in the cortical intermediate zone. They do not resemble the cells migrating by locomotion or somal translocation. Instead these multipolar cells express neuronal markers and extend multiple thin processes in various directions independently of the radial glial fibers.[9]

References

  1. See also time lapse sequences of radial migration (also known as glial guidance) and somal translocation.
  2. 2.0 2.1 Nadarajah B, Brunstrom J, Grutzendler J, Wong R, Pearlman A (2001). "Two modes of radial migration in early development of the cerebral cortex". Nat Neurosci 4 (2): 143–50. DOI:10.1038/83967. PMID 11175874. Research Blogging.
  3. Samuels B, Tsai L (2004). "Nucleokinesis illuminated". Nat Neurosci 7 (11): 1169–70. DOI:10.1038/nn1104-1169. PMID 15508010. Research Blogging.
  4. Tamamaki N, Nakamura K, Okamoto K, Kaneko T (Sep 2001). "Radial glia is a progenitor of neocortical neurons in the developing cerebral cortex". Neurosci. Res. 41 (1): 51–60. DOI:10.1016/S0168-0102(01)00259-0. PMID 11535293. Research Blogging.
  5. Miyata T, Kawaguchi A, Okano H, Ogawa M (Sep 2001). "Asymmetric inheritance of radial glial fibers by cortical neurons". Neuron 31 (5): 727–41. DOI:10.1016/S0896-6273(01)00420-2. PMID 11567613. Research Blogging.
  6. Nadarajah B, Parnavelas J (2002). "Modes of neuronal migration in the developing cerebral cortex". Nat Rev Neurosci 3 (6): 423–32. DOI:10.1038/nrn845. PMID 12042877. Research Blogging.
  7. Rakic P (1972). "Mode of cell migration to the superficial layers of fetal monkey neocortex". J Comp Neurol 145 (1): 61–83. DOI:10.1002/cne.901450105. PMID 4624784. Research Blogging.
  8. Letinic K, Zoncu R, Rakic P (Jun 2002). "Origin of GABAergic neurons in the human neocortex". Nature 417 (6889): 645–9. DOI:10.1038/nature00779. PMID 12050665. Research Blogging.
  9. 9.0 9.1 Tabata H, Nakajima K (Nov 2003). "Multipolar migration: the third mode of radial neuronal migration in the developing cerebral cortex". J Neurosci 23 (31): 9996–10001. PMID 14602813.
  10. Nadarajah B, Alifragis P, Wong R, Parnavelas J (2003). "Neuronal migration in the developing cerebral cortex: observations based on real-time imaging". Cereb Cortex 13 (6): 607–11. DOI:10.1093/cercor/13.6.607. PMID 12764035. Research Blogging.