photo

Séminaires MSC
"Matière et Systèmes Complexes"

                      
Lundi 20 juin 2005 à 11h30
Tour 33, couloir 33-43, 2ème étage, salle de réunion

Jean Louis Bessereau
(ENS, Paris)

Analyse génétique de la synaptogenèse dans un système simple, le nématode C. elegans.

Chemical synapses are specialized sites of cell contact capable of relaying information from one cell to another quickly and with high fidelity. These biophysical properties are due, in part, to the spatial relationships between the synaptic vesicle exocytosis machinery and the postsynaptic neurotransmitter-sensing apparatus. We are using the simple model organism C. elegans which only contains 302 neurons to characterize the precise spatial organization of the synapse in the living state and to identify novel genes and mechanisms involved in receptor clustering.
High-pressure freezing of a living animal combined with morphological and immuno-electron microscopy provides a mean to catch the synapse in suspended animation. By quantitative analysis of pre- and post-synaptic proteins distribution, we established a functional topomap of the synapse at electron microscopy resolution. It  reveals a striking match between the area of synaptic vesicles release and the distribution of post-synaptic receptors.
To identify components of the receptor clustering machinery, we conducted genetic screens. Specifically, we cloned the gene lev-10, which encodes a novel transmembrane protein required for acetylcholine receptor clustering (AChR). The ectodomain of LEV-10 is sufficient to achieve AChR aggregation in vivo, thus suggesting a novel mechanism for AChR clustering relying on extracellular protein interactions.