Guidance of Axons in the Nervous System

A number of proteins have been identified in insect embryos which have structural features suggestive of a role in axon guidance but which, unlike the fasciclins, show a widespread distribution within the nervous system. It should be noted that... 

Work on identifying the molecules responsible for axon guidance in invertebrate nervous systems has been underway for only a few years, yet already a number of candidate recognition molecules have been characterized. We can confidently expect this list to grow rapidly as an arsenal of powerful genetic and molecular techniques is brought to bear on the problem. 

Tessier-Lavigne, M., Placzek, M., Lumsden, A.G.S., Dodd, J. and lessen, T.M. (1988) Chemotropic guidance of developing axons in the mammalian central nervous system. Nature 336 775-778. 

Understanding how the nervous system is wired up during development is important for understanding both how neurological disorders based on wiring defects can be avoided, and how axons can be made to regenerate appropriately after injury. In the past 15 years or so several families of guidance molecules... 

Cell adhesion molecules (CAMs) play critical roles in all facets of nervous system development and maintenance. Important phenomena in which CAMs are involved include initial formation of the neural tube and the neural crest, migration of all neurons and glial cells, axonal outgrowth and guidance, target selection, synaptic stabilization and plasticity, myelination and nerve regeneration after injury (see Chs 4,24,28-30 and 53). Adhesion molecules interact with each other and with nonadhesive cell-surface and/or cytoplasmic molecules, and, in the two... 

The 2-OST null mutant has been described in C. elegans as well. Surprisingly, 2-OST-deficient mutants are viable and fertile without any locomotory defect or embryonic paralysis as observed in perlecan-deficient worms. The phenotypes of 2-OST null worms are only detectable in nervous system development by displaying axonal guidance and migration defects in a neuron-type specific manner. These findings suggest that the 2-0-sulfation of HS plays very specific roles in metazoan development. These roles may vary in the developmental schemes of different species. 

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