Fig. 2
From: Commissural axon guidance in the developing spinal cord: from Cajal to the present day
Comparison of netrin1 axon guidance models. a In the chemotaxis model, netrin1 acts as a long-range guidance signal. Commissural axons grow towards a diffusible source of netrin1 protein (green) emanating from the floor plate (FP). b In the haptotaxis model, netrin1 acts as a short-range guidance cue. Neural progenitor cells (NPCs) in the ventricular zone (VZ) express netrin1 transcript (red). Netrin1 protein (green) is trafficked to the pial surface along the radial processes of the NPCs to form a growth substrate. Commissural axons extend along this netrin1 substrate, themselves accumulating netrin1 as they grow around the VZ towards the FP. Figure adapted from [13]