Project Summary While a growing body of work has contributed to our understanding of synapse assembly, less is known about how synapses are maintained throughout life. This long life of synapses is crucial for the sustained function of neural circuits, including those supporting cognition, movement, and other vital functions. However, maintaining long-lived synaptic connections presents a cell biological challenge, as synaptic proteins have finite lifetimes, synaptic vesicles turnover rapidly, and protein synthesis is scarce in the presynaptic compartment. This project will study the mechanisms of presynaptic maintenance, using C. elegans as a model system. In Aim 1, I will investigate the proteins involved in maintaining synaptic structures, using the auxin-inducible degron system to remove the candidate proteins SYD-2, SYD-1, SAD-1, CDK-5, and PCT-1 from the mature nervous system. Changes in synapse organization will be assessed using endogenous, cell-type specific markers of synaptic vesicles and active zone proteins. In Aim 2, I will identify regulators of the presynaptic scaffolding protein SYD-2. I will implement a visual forward genetic screen to identify candidates that regulate SYD-2 stability, using a pulse-chase SYD-2 HaloTag approach to visualize SYD-2 turnover. In Aim 3, I will identify regulators of SYD-2 through the use of Split-TurboID proximity biotinylation to detect interacting partners of SYD-2 in the presynaptic compartment. Candidate regulators of SYD-2 turnover will be assessed using the SYD-2 HaloTag system. This work will identify key synaptic maintenance proteins and their regulators. Understanding the mechanisms that maintain stable synapses provides therapeutic avenues for preserving synapses in aging and neurodegenerative diseases. This project, performed in the laboratory of Dr. Kang Shen at Stanford University, provides a strong training opportunity for me in the fields of cell biology and neuroscience, and I will gain new experience with the C. elegans model system, genetic manipulations, and microscopy.