Venue: Module 1.2, Bâtiment CROUS, 1er étage.
Zoom link https://u-bordeaux-fr.zoom.us/j/81586413997?pwd=akJzajlWTitOcjhsUnV4Q3NHRGtpZz09
Title
Super-resolution analysis of the nano-anatomical determinants of the synaptic function of hippocampal neurons
Abstract
Synapses are the core of neuronal communication in the mammalian brain, mediating rapid and flexible transmission of electrical signals. Excitatory synaptic transmission is conveyed from presynaptic terminals to postsynaptic spines, small protrusions stemming from dendrites, possessing a unique morphology. In the hippocampus, the function and regulation of excitatory synapses play central roles in higher brain functions such as learning and memory. These synapses are finely tuned by activity-dependent changes that are intricately linked to the morphology of dendritic spines. Therefore, elucidating the relationship between the morphology and the function of dendritic spines is crucial for understanding how neurons process and store information. In particular, the size and length of the spine neck can significantly impact the electrical properties of the synapse. A longer, narrower spine neck could act as an electrical barrier, limiting the spread of voltage and current from the spine head to the dendrite and ultimately to the soma.
However, the exact mechanism by which spine neck morphology acts as an electrical modifier for the synapse remains only partially understood, because of considerable technical challenges involved in investigating the biophysical, morphological, and functional properties of dynamic and small dendritic spines. To investigate the complex relationship between the morphology and the function of spines, it is crucial to develop an experimental setup capable of simultaneous observation and perturbation of the morphology and function of synapses.
To tackle these challenges a custom experimental setup was modified to incorporate time-lapse STED microscopy, functional imaging, 2-photon glutamate uncaging, and patch-clamp electrophysiology on a single microscope platform. Specifically, I implemented a system based on an inverted home-made 3D-STED microscope with a second laser scanner enabling simultaneous control of two laser spots within the sample. I validated that this system allowed to perform precise targeting of a 2-photon laser spot for glutamate uncaging near specific spine synapses while concurrently visualizing their morphology through STED or recording functional calcium events. Using super-resolution microscopy analysis, I reported a diversity of spine morphologies and biophysical properties (such as neck widths, lengths and resistances) in hippocampal organotypic slices. To directly link morphologies and functional properties, I activated pairs of STED-resolved spines with opposite neck morphologies (long and thin, wide and short) using single spine 2-photon glutamate uncaging while simultaneously recording patch-clamp somatic uncaging excitatory postsynaptic potentials (uEPSPs) and currents (uEPSCs).
This methodology has the potential to be a valuable tool for investigating the intricate structure-function relationship at the nanoscale during synaptic plasticity.
Keywords: dendritic spines, hippocampal organotypic slices, STED microscopy, 2-photon glutamate uncaging, electrophysiology, dual scanner system
Publication
Arizono M, Idziak A, Quici F, Nägerl UV.
Getting sharper: the brain under the spotlight of super-resolution microscopy.
Trends Cell Biol.
2023 Feb;33(2):148-161. doi: 10.1016/j.tcb.2022.06.011. Epub 2022 Jul 26. PMID: 35906123.
Jury
Dr. Jérôme Baufreton
Prof. Martin Fuhrmann
Dr. Judit Makara
Dr. Agnès Nadjar