Cell adhesion protein (PubMed:15035988). Determines synapse formation (PubMed:15035988, PubMed:21858180, PubMed:24485456). Required for correct localization of syg-1 at synaptic sites (PubMed:15035988). Interacts with syg-1. Expressed in vulval epithelial cells. Expressed in head neurons and body wall muscles during embryogenesis (PubMed:15035988). Expressed in head and body wall muscles and in punctate structures near the ventral nerve cord during larval stages L1 and L2 (PubMed:15035988). Expressed in primary vulval epithelial cells from larval stage L3, with expression increasing upon entry into L4 and diminished within six hours of adulthood (PubMed:15035988, PubMed:18675916). The first five extracellular Ig-like domains are required for correct localization of syg-1. The cytoplasmic domain is necessary for syg-2 subcellular localization. Animals are viable, fertile, egg-laying proficient and coordinated. Abnormal synaptic vesicle clustering in the HSNL motor neuron from larval stage L3 through to adulthood. Reduced accumulation of synaptic vesicle proteins snb-1 and cat-1 in HSNL motor neuron. Defective synapse specificity due to altered distribution of synapses. syg-1 is mis-localized and diffusely distributed on the axon of the HSNL neuron.