In the central nervous system (CNS), neuroblasts, postmitotic neurons, and glial cells migrate along stereotyped routes from their birthplace to their final destination. Two main types of neuronal migration have been distinguished: a radial one for neurons that migrate along radial glia in a direction perpendicular to the pial surface and a tangential mode for neurons which migrate along other neurons or axons, independently of radial glia (Marin O, Rubenstein JL, Annu Rev Neurosci 26: 441-483, 2003; Metin et al, J Neurosci 28(46):11746-11752, 2008). The initiation of migration, the direction followed by migrating neurons or glia, and their decision at specific choice points are influenced by molecules in the environment of the neurons and by intrinsic developmental programs. Many studies in various systems have shown that semaphorins and their receptors play an essential role in this process. Semaphorins influence the motility of neurons and oligodendrocytes and also shape the pathway they follow during their migration. Here, I review these results, focusing on the vertebrate CNS and a few model systems.
Keywords Neural stem cells • Cerebellum • Granule cells • Centrosome • Oligodendrocytes • GnRH
Semaphorins Control the Radial Migration of Cortical NeuronsThe six-layered mammalian neocortex contains two main types of neurons: (1) pyramidal neurons that primarily project outside the cortex and originate from the ventricular zone of the dorsal telencephalon, or pallium; and (2) interneurons, which make local connections between different layers or across layers and originate from the ganglionic eminence in the ventral telencephalon or subpallium (Rakic 2009; A. Chédotal ( )