May control axon guidance across the CNS (By similarity). Prevents the delivery of ROBO1 at the cell surface and down-regulates its expression (By similarity). Interacts (via cytoplasmic domain) with WW domain-containing proteins MAGI1, MAGI3, NEDD4, NEDD4L, WWTR1/TAZ and YAP1. Gamma-carboxyglutamate residues are formed by vitamin K dependent carboxylation. These residues are essential for the binding of calcium. Belongs to the commissureless family.