Cell surface receptor that plays a functionally redundant role in the inhibition of neurite outgrowth mediated by MAG. It plays a functionally redundant role in postnatal brain development. Contributes to normal axon migration across the brain midline and normal formation of the corpus callosum. It does not seem to play a significant role in regulating axon regeneration in the adult central nervous system. Protects motoneurons against apoptosis; protection against apoptosis is probably mediated by MAG. Like other family members, plays a role in restricting the number dendritic spines and the number of synapses that are formed during brain development.