Axon guidance in invertebrates

In contrast to the paucity of evidence for diffusible, chemotropic factors in invertebrates, a large number of observations support a role for substrate-associated factors in axon guidance. Such factors appear to be located on a variety of cellular and extracellular structures. Precise identification of these structures is indispensable for characterising the molecular nature of the axon guidance factors and elucidating their function. The various classes of cellular structures implicated in axon guidance in invertebrates are considered in turn, below. 

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. 

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