Neuronal Activity Contributes to Synaptic Partner Recognition in Caenorhabditis elegans

The nervous system consists of many neurons that form organized neural circuits through synaptic connections. Neurons must identify their correct synaptic partner in order to form a synapse and then maintain appropriate connections. Synaptic partner recognition is a fundamental process in the development of the nervous system, however it is poorly understood. Previous research in our laboratory indicates that synaptic activity contributes to synaptic partner recognition. Specifically, synapses between sensory neurons and interneurons in the genetic model organism C. elegans are severely reduced in animals with mutations in the voltage-gated calcium channel alpha subunit unc-2.  The goal of this study is to investigate the effects of synaptic activity on the formation of synapses with a second calcium channel alpha subunit mutant, cca-1. The cca-1 gene is involved in synaptic transmission, promoting the release of neurotransmitters into the synaptic cleft. We label synaptic connections using the Neuroligin-1 mediated GFP Reconstitution Across Synaptic Partners (NLG-1 GRASP), a method previously developed by our group to label synapses between PHB sensory neurons and AVA interneurons. We find that cca-1 mutants have reduced NLG-1 GRASP signal, indicating a reduction in appropriate synaptic contacts between the neurons. Our results confirm that sensory activity contributes to synaptic partner recognition. We will conduct a time-course to understand if cca-1 affects establishment or maintenance of correct synapses, and investigate other synaptic transmission mutants to corroborate the effect of activity on synaptic partner recognition.