Nanoscale imaging of synapse morphology in the mouse neocortex in vivo by two-photon STED microscopy
Defended on November 25, 2016
Valentin Nagerl’s team : Synaptic Plasticity and Superresolution Microscopy group – IINS
Expertise : Pump-Dump-Probe-Spectroscopy, Higher Harmonic Generation Microscopy, Electrophysiology, 2P-STED Microscopy, Stereotaxic virus injections, Immunochemistry
The brain is a complex organ consisting of neurons and non-neuronal cells. Communication between neurons takes place via synapses, whose morphological remodeling is thought to be crucial for information processing and storage in the mammalian brain. Recently, this neuro-centric view of synaptic function has evolved, also taking into account the glial processes in close vicinity of the synapse. However, as their structure is well below the spatial resolution of conventional light microscopy, progress in investigating them in a
physiological environment, the intact brain, has been impeded. Indeed, little is known on the nanoscale morphological variations of dendritic spines, the interaction with glial processes, and how these affect synaptic transmission in vivo.
Here, we aim to visualize the dynamic nano-morphology of dendritic spines, and possibly also glial processes, in mouse somatosensory cortex in vivo. We therefore implemented super-resolution 2P-STED time lapse imaging, which allows for high spatial resolution and deep tissue penetration, in anesthetized mice. We show that the nano-morphology of spines is diverse, dynamic, but overall stable, and that differences in spine morphology can have an effect on spine biochemical compartmentalization in vivo. Moreover, implementation of dual color in vivo super-resolution imaging and a novel astrocytic labeling approach provided the first steps towards nanoscale characterization of neuron-glia interactions in vivo.
These findings bring new insights in synapse dynamics at the nanoscale in vivo, and our
methodological endeavors help pave the way for a better understanding of how nanoscale aspects of spine morphology and their dynamics might contribute to brain physiology and
Keywords: Super resolution microscopy, Two-Photon (2P-) STED microscopy, in vivo brain preparation, dendritic spines, FRAP, spine compartmentalization, dual color imaging, glial processes
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- Giovanni Marsicano
- Bruno Weber
- Fritjof Helmchen
- Laurent Cognet
DR CNRS (Examiner/Examinateur)
- Detlev Schild
Supervisor / Directeur de thèse: U. Valentin Nägerl, Professor/Professeur
Team Leader IINS