The morphogen sonic hedgehog collaborates with netrin-1 to guide axons in the spinal cord.

Netrin-1 is an attractive axon guidance molecule required for the proper navigation of commissural axons to the floor plate in the spinal cord. A new study now shows that sonic hedgehog (Shh) from midline structures collaborates with netrin-1 to guide commissural axons. This new role for the morphogen Shh raises the possibility that principles similar to those used to establish positional information in embryonic patterning are also employed during axon navigation.