Shh and Wnts, secreted by the floor and roof plate of the spinal cord, direct longitudinal growth of the axons from the adjacent ventral funiculus and cortico-spinal tract. Whether these midline cues influence the directionality of axons elongating in more lateral positions of the spinal cord is unexplored. Song and colleagues investigate this possibility and demonstrate that the location of descending raphe-spinal tract in the ventrolateral spinal cord is dictated by the simultaneous repellent activity of Shh gradients in both the anterior-to-posterior (A-P) and medial-to-lateral (M-L) axis.
- Paola Bovolenta
- Luisa Sanchez-Arrones