MSc Exit Seminar – Christine Nguyen (Stewart lab)

MSc Exit Seminar

Monday November 23^rd, 9:30 am – Room DV 3130, University of Toronto at Mississauga

Christine Nguyen (Stewart lab)

“The Influence of Postsynaptic Structures on Missing Quanta at the Drosophila Neuromuscular Junction”

Abstract

Synaptic transmission requires both pre- and post-synaptic elements for neural communication. The postsynaptic structure contributes to the effectiveness of synaptic currents to induce voltage changes in postsynaptic cells. At the Drosophila neuromuscular junction (NMJ), the subsynaptic reticulum (SSR) consists of elaborate membrane folds that link the synaptic contacts to the muscle, but its role in synaptic physiology is poorly understood. In this study, I investigate the function of the SSR by conducting electrophysiological experiments on genetic mutants that up- or down-regulate SSR complexity. I observed that some synaptic currents do not result in postsynaptic voltage changes, events called ‘missing quanta’. Furthermore, the frequency of missing quanta is positively correlated with SSR complexity, observed in both naturally occurring variations of the SSR and in genetic mutants. Based on cable theory, I develop an electrical circuit framework to propose that the SSR contributes to the missing quanta by acting as a filter or a switch for some synaptic events. Further studies directed at understanding the role of the SSR in synaptic transmission and the potential for regulating ‘missing quanta’ will yield important information about synaptic transmission at the Drosophila NMJ.