Distinct subpopulations of sensory afferents require F11 or axonin-1 for growth to their target layers within the spinal cord of the chick

Dorsal root ganglion neurons project axons to specific target layers in the gray matter of the spinal cord, according to their sensory modality. Using an in vivo approach, we demonstrate an involvement of the two immunoglobul in superfamily cell adhesion molecules axonin-1/TAG-1 and F11/F3/contactin in subpopulation-specific sensory axon guidance. Proprioceptive neurons, wh ich establish connections with motoneurons in the ventral horn, depend on F 11 interactions. Nociceptive fibers, which target to layers in the dorsal h orn, require axonin-1 for pathfinding. In vitro NgCAM and NrCAM were shown to bind to both axonin-1 and F11. However, despite this fact and despite th eir ubiquitous expression in the spinal cord, NgCAM and NrCAM are selective binding partners for axonin-1 and F11 in sensory axon guidance. Whereas no ciceptive pathfinding depends on NgCAM and axonin-1, proprioceptive fibers require NrCAM and F11.