Figure 2.

Multiple guidance cues control the pathfinding of spinal cord commissural axons along the dorsal–ventral axis. In a transverse view, precrossing commissural axons (blue axon) are attracted by Netrin-1 (green) and Shh (cyan), which are highly enriched in the floor plate and present in the ventral to dorsal decreasing gradient. Chemorepellants, such as the BMPs (red) and Draxin (orange), repel commissural axons from the dorsal midline to orient commissural axons to grow ventrally.