Probable cell adhesion protein involved in patterning of the nervous system, playing a role in ALM and PLM touch receptor axon growth and VNC axon navigation (PubMed:23123963). By associating with the transmembrane protein sax-7, mediates axonal interactions to establish synaptic connections between the AVG interneuron and the two PHC sensory neurons (PubMed:28901288). Also required for non-neuronal cell migration in the excretory canal, regulating excretory canal elongation and excretory cell morphogenesis (PubMed:23123963). Plays a role in regulating male mating behavior (PubMed:28901288). Interacts with sax-7; the interaction establishes synaptic connections between neurons. Expressed in neurons including the I1 and I3 pharyngeal interneurons, NSM and VNC motor neurons, HSN and CAN neurons, the ALM and PLM touch receptor neurons and other unidentified head neurons (PubMed:23123963). Expressed in AVG interneurons (PubMed:28901288). Also expressed in somatic muscles, the excretory canal, the excretory cell and the hypodermis (PubMed:23123963). Expressed throughout embryonic development and adulthood. RNAi-mediated knockdown results in truncated or shorter excretory canals, and also truncated ALM axons that fail to extend above the nerve ring, truncated PLM processes and abnormal VNC axon patterning. Belongs to the immunoglobulin superfamily. Contactin family.