Axon guidance molecules

Somatic motor and sensory neurons that give rise to PNS axons maintain large fractions of their total protoplasmic bulk within the CNS. Many of the extracellular matrix components and axonal guidance molecules involved in... 

STRUCTURES OF AXON GUIDANCE MOLECULES AND THEIR NEURONAL RECEPTORS... 

No single cellular axon guidance cue appears to be unique to a particular invertebrate group or class of neuron and hence one cannot a priori exclude any specific cellular structure as the site of axon guidance molecules. Therefore, the cellular identity of guidance factors needs to be established anew every time one begins to work with a new system. 

Forscher and Smith, 1988). In this view, any molecule on the membrane of the growth cone that takes part in a receptor-ligand interaction leading to intracellular changes of the type referred to above could be considered to be an axon guidance molecule - a definition that encompasses a far wider variety of molecules than those traditionally considered to be cell adhesion molecules. 

The labelled pathways hypothesis, developed by Goodman and co-workers to explain the specific choices of axonal pathways made by growth cones in insect embryos (see Section 3.3.1), predicts the existence of a set of axon guidance molecules with a highly specific and restricted distribution on central and peripheral axonal pathways. 

Several workers have searched for molecules that meet these criteria and these searches have resulted in identification of a number of candidate axon guidance molecules, the best characterized being the fasciclin family. 

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