Sensing and Imaging Synaptic Vesicle Trafficking and Neurotransmitter Release - A Novel Opto-Synaptic Interface

The University of Exeter (UoE) and Nanyang Technological University (NTU), Singapore are offering six fully funded postgraduate studentships to undertake collaborative research projects at the two institutions, leading to PhD degrees (split-site) to be conferred either by the UoE or NTU.

Students pursuing these postgraduate research projects will benefit from the unique opportunity to conduct their research at both institutions. Students will be registered at one or other institution, where they will be based for the majority of their time, but will spend at least 12 and not more than 18 months at the partner institution over the duration of the programme. The frequency and length of stays at each institution will be agreed with successful candidates prior to offers being made.

Project Description:

This doctoral studentship will enable development of WGM sensors as a novel tool for the detection of neuronal synaptic vesicles (SVs) and the direct detection of synaptic activity at the single-molecule level. SVs are a key organelle in brain function, because they store and release the neurotransmitters that are used for inter-neuronal signalling. Imaging individual SVs at the light-microscope level has been a challenge, due to the very small size (approximately 40 nm in diameter) of SVs. The goal is to determine the stoichiometry and structure of SV aggregates and to characterise the role they play in synaptic vesicle trafficking and the transmission of information between nerve cells. SVs aggregate to form a “reserve pool” of SVs that are mobilised to maintain synaptic transmission during sustained neuronal activity. Thus, being able to sense and visualise these SV clusters in living neurons is important to understand the dynamics of synaptic transmission. It is particularly relevant to clarify the roles of the SV binding proteins called synapsins. It was previously hypothesized that these proteins control the formation of aggregates during mobilization of reserve vesicles in rapidly-firing neurons (6). Elucidating the interplay of synapsin isoforms in SV aggregation and trafficking has important implication for diseases such as epilepsy, schizophrenia and other brain disorders (7).The relative amounts of two synapsin isoforms, synapsins IIA and IB, may constitute a novel signal to control the vesicle replenishment and the dynamics of electro-chemical signalling at the synapse.

In this project, a student will develop novel label-free optical sensing and imaging modalities for nanoscale synaptic processes, combining advanced optical WGM sensors with label-based fluorescence imaging and single-cell electrophysiological modalities. The overall aim of this fellowship is to elucidate the role of synapsin IB and IIA in the regulation of neuronal vesicle dynamics, vesicle aggregation, and vesicle replenishment. Sensing and imaging tools will be developed to visualise the vesicular aggregates, determine the number of vesicles in each aggregate, and determine the protein-vesicle stoichiometry as a function of different synapsin isoforms and their concentrations. The modulation of the dynamics vesicle trafficking by synapsin proteins will be explored on previously inaccessible timescales down to micro-and nanoseconds in vitro reconstituted sensing assays (5). In the second part of the project, the analysis of the dynamical processes in the synapse will be extended to the single molecule level. Leveraging previous progress in techniques for getting neurons to innervate artificial substrates (8), artificial synapses will be formed between nerve cells and optoplasmonic WGM sensors capable of detecting the release of neuronal transmitters down to the single-molecule level. For the first time, an optical interface for the label-free readout of neuronal activity will be established.

The student will have the possibility to combine state-of-the art imaging/ electrophysiology (Augustine) with state-of-the-art nanosensors (Vollmer) to establish an entirely novel platform technology for the analysis of synaptic vesicles, down to the level of single-molecules. This collaborative research will bring about breakthroughs in optical technologies for sensing/neuroscience, which require the joint efforts by the Augustine/Vollmer labs. The doctoral student will have access to state of the art technology that are not available in this combination anywhere else in the world. This will uniquely position the student to acquire skills and training in sensing and imaging which cannot be obtained in any other fellowship or training programme. The fellowship is cutting across disciplines and is ideally supported by the NTU-Exeter partnership aimed at advancing interdisciplinary research and nucleating entirely new fields of studies at the boundaries of physics and biology.

To apply for this project please visit http://www.exeter.ac.uk/studying/funding/award/?id=3054