Required for synapse development in the active zone of presynaptic terminals of specific neurons including serotonergic NSM neurons (PubMed:29160205). The active zone is a protein-dense neuronal region within the presynaptic bouton, from which synaptic vesicles send neurotransmitter signals across the synapse (PubMed:29160205). Plays a role in the recruitment and clustering of synaptic vesicles in the active zone of presynaptic terminals in serotonergic NSM neurons, and coordinates the release of synaptic vesicles at presynaptic terminals to regulate neurotransmission at neuromuscular junctions (PubMed:29160205). Regulates synapse number in inhibitory motor neurons and plays a role in spontaneous postsynaptic synaptic vesicle release in muscle cells (PubMed:29160205). Localization at the synapse may depend on other active zone proteins such as syd-1 and syd-2 (PubMed:29160205). Anchored via the C-terminus to the active zone, a protein-dense region within the presynaptic bouton, of the synaptic compartment (PubMed:29160205). The N-terminus extends away from the active zone (PubMed:29160205). Expressed in the nervous system. Expressed in the nervous system from the three-fold stage of embryonic development. Produced by alternative splicing. Produced by alternative promoter usage and alternative splicing. Produced by alternative promoter usage. Produced by alternative promoter usage. Produced by alternative promoter usage and alternative splicing.