Guidance cue

Signals in response to extracellular guidance cues cause growth cones to steer probably involve multiple pathways... 

Gallo, G. and Letourneau, P. C. Regulation of growth cone actin filaments by guidance cues. /. Neurobiol. 58 92-102, 2004. 

Webster, D. R. and Weissburg, M. J. (2001). Chemosensory guidance cues in a turbulent chemical odor plume. Limnology and Oceanography 46,1034-1047. 

Wadsworth WG, Hedgecock EM. 1996. Hierarchical guidance cues in the developing nervous system of C. elegans. Bioessays 18 355-362. 

Directed axon growth involves active recognition of guidance cues... 

A variety of observations of axon growth both during normal development and in response to surgical transplantation of neuronal targets (reviewed in Goodman and Shatz, 1993) also provide indirect support for chemotropic guidance cues in vertebrates. 

Therefore, it appears that while guidepost neurons may be used as cues to guide the growth of later appearing axons, such neurons are not always necessary. Other axon guidance cues must be available in these situations. 

Halpem et al. (1991) and Sink and Whitington (1991a) have also reported a close association between the axons of embryonic motoneurons and muscles in the Drosophila embryo. As the RP motor axons advance to their target muscles, they traverse three sheets of muscle fibres. Each motor axon branches extensively over these muscles, including non-target muscles. It thus appears as if the muscles in this sheet contain a guidance cue or cues, which can be recognised by all of the RP... 

Guidance cues on epithelial cells and/or associated basal laminae... 

Do guidance cues reside on the epithelial cells or on their basal laminae ... 

An electron-microscopic study showed that growth cones and filopodia of the Til neurons in the embryonic grasshopper limb bud contact the basal lamina, rather than the ectoderm of the limb bud (Anderson and Tucker, 1988). These authors concluded that guidance cues for these axons reside in the basal lamina, rather than the ectoderm. They also found that there is a proximal-distal gradient in basal lamina structure, with thinner basal lamina at the tip and thicker at the base (Anderson and Tucker, 1989). This correlates with the proximal-distal orientation of the pioneering Trl axons and it was suggested that this correlation may be a causative one for guidance of the Trl axons. 

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. 

Growth cones can be considered to be opportunistic in their choice of guidance cues any stmcture in the environment of the growth... 

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