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Christian Stigloher "Electron Tomographic and Genetic Dissection of Synaptic Architecture and Function in C. elegans"

Abstract :

The functionality of the synapse is crucially linked to the spatial organization of its ultrastructural components.
On the presynaptic side, the active zone (AZ) is a specialized domain where vesicles fuse with the plasma membrane to release neurotransmitters. Efficient signalling requires synaptic vesicles (SVs) to be recruited, primed and retained in close proximity to voltage-dependent calcium channels. The electron-dense projections situated at the center of the AZ might provide a hub for the spatial coordination of these processes.
High resolution 3D analysis of synapses in C. elegans has up to now been hampered by the low resolution of classical electron microscopy (EM) imaging in the z-axis. In order to produce a seamless 3D model of synaptic architecture, we have adapted electron tomography that yields high resolution image stacks in 3D in samples with up to several hundred nm thickness. This allowed us to study architectural features and their functional roles by comparing wild type with mutants disrupting AZ components:
First, we found a densely interconnected network of filaments within the synapse comparably to the cytomatrix filaments described in vertebrates. Second, we analyzed the 3D architecture of the dense projection in the center of the AZ with filaments directly contacting SVs in the interior of the presynapse as well as docked SVs. Third, we investigated the functional components of these connections by analyzing mutants disrupting two key AZ proteins: UNC-10/RIM and SYD-2/liprin. The number of contacts between SVs and the dense projection was significantly lowered in both mutants. Similar to unc-10 mutants, the dependence of SV fusion on extracellular calcium concentration was increased in syd-2 mutants compared to wild type. Therefore, we propose that the dense projections mediate efficient coupling of primed vesicles with calcium signalling by clustering them at the AZ via UNC-10/RIM and SYD-2/liprin dependent mechanisms.

Selected publications

The Presynaptic Dense Projection of the Caenorhabiditis elegans Cholinergic Neuromuscular Junction Localizes Synaptic Vesicles at the Active Zone through SYD-2/Liprin and UNC-10/RIM-Dependent Interactions.Stigloher C, Zhan H., Zhen M., Richmond JE, Bessereau JL. Journal of Neuroscience, 2011 Mar 23;31(12):4388-96.
Gsk3beta/PKA and Gli1 regulate the maintenance of neural progenitors at the midbrain-hindbrain boundary in concert with E(Spl) factor activity.
Ninkovic J*, Stigloher C*, Lillesaar C*, Bally-Cuif L.
Development. 2008 Sep; 135(18):3137-48.
MicroRNA-9 directs late organizer activity of the midbrain-hindbrain boundary.Leucht C*, Stigloher C*, Wizenmann A, Klafke R, Folchert A, Bally-Cuif L.
Nature Neuroscience. 2008 Jun; 11(6):641-8.
Segregation of telencephalic and eye-field identities inside the zebrafish forebrain territory is controlled by Rx3.Stigloher C, Ninkovic J, Laplante M, Geling A, Tannhäuser B, Topp S, Kikuta H, Becker TS, Houart C, Bally-Cuif L.Development. 2006 Aug; 133(15):2925-35.

Scientific focus :

2008-now: Postdoc in the lab of Dr. Jean-Louis Bessereau at the ENS in Paris, France
2004-2008: PhD in the lab of Dr. Laure Bally-Cuif at the Technical University Munich and Helmholtz Center Munich, Germany
1999-2004: Studies in Biology at the Biocenter of the University of Würzburg, Germany, and Duke University, North Carolina

Valentin Nagerl