A synapse is a functional contact between two nerve cells (neurons). Chemical synapses utilize compounds called neurotransmitters, which are molecules that are released from the pre-synaptic cell to cross the tiny cleft between the cells, and so transmit signals from one neuron to another. This project utilizes synapses within the compound eye of a fruitfly, Drosophila, as a model system to identify proteins responsible for synaptic signaling in the visual pathway. The Drosophila eye offers the clear advantage of its well-known genetics to exploit mutations in visual deficiencies that are easy to screen. A novel combination of biochemistry and genetic techniques is used here to identify proteins that are important in the basic functions of neurotransmitter synthesis, packaging and release. Identifying molecules involved in transmitter release and localization is a first step in understanding the complex series of events in signal transmission across a synapse. Results will have impact not only on understanding synaptic mechanisms at the molecular level, but also on the genetic control of such mechanisms, on understanding visual function in the eye, and on processes in general cell biology involving cellular carrier vesicles.