Neurons Take Shape Current Biology Haeryun Lee, David Van Vactor  Current Biology  Volume 13, Issue 4, Pages R152-R161 (February 2003) DOI: 10.1016/S0960-9822(03)00080-0

Figure 1 The cytoskeletal elements of the growth cone. (A) A cartoon of a growth cone shows the relationship of the peripheral and central domains, relative to the nascent axon shaft. This growth cone is encountering a local attractive cue (green arrowhead) resulting in a local cytoskeletal response of increased net actin assembly at the leading edge (orange perimeter with arrows) that induces a polarization in the motility machinery and a change in direction (purple arrow). (B) An inset corresponding to the boxed region in (A) reveals the two major types of F-actin array – filopodial actin bundles and actin networks in the veils – within the peripheral domain. F-actin is assembled proximal to the membrane through monomer addition to ‘plus’ ends of microfilaments. The assembled network then is translocated backwards toward the central domain. (C) As F-actin bundles are pulled back into the transition zone between peripheral and central domains, highly dynamic microtubules interact with these F-actin structures. As a growth cone turns toward the source of an attractive cue, the plus ends of some pioneer microtubules extending into the peripheral domain are captured (or recruited) in the direction of the turn. Filopodia in this region of the leading edge will dilate as these microtubules become stabilized, forming the shaft of the newly formed axon shaft. Current Biology 2003 13, R152-R161DOI: (10.1016/S0960-9822(03)00080-0)

Figure 2 A series of cytoskeletal activities within the growth cone. From the membrane of the leading edge, back towards the body of the growth cone, and the nascent axon shaft, a complex series of cytoskeletal events occur. Each step in this process will involve sets of actin- and tubulin-binding proteins that may be coordinated in the cellular response to axon guidance factors. Current Biology 2003 13, R152-R161DOI: (10.1016/S0960-9822(03)00080-0)

Figure 3 A summary of major axon guidance cues and their receptors. Although many other molecules have been shown to influence growth cone behavior in different assay systems, this list of ligand classes (on the left) and their growth cone receptors (on the right) represents the major classes of cell surface and secreted guidance factors whose activity has been confirmed in vivo (reviewed in [30,31]). Current Biology 2003 13, R152-R161DOI: (10.1016/S0960-9822(03)00080-0)