Neurotransmitters are released from a specific site in the axon terminal called the active zone, which is composed of synaptic vesicles and a meshwork of cytoskeleton underlying the plasma membrane. The protein encoded by this gene is thought to be a scaffolding protein involved in organizing the presynaptic cytoskeleton. The gene is expressed primarily in neurons in the brain. A similar gene product in rodents is concentrated in the active zone of axon terminals and tightly associated with cytoskeletal structures, and is essential for regulating neurotransmitter release from a subset of synapses.