Contact: Jean-Baptiste Sibarita
We have a transdisciplinary approach to study the interplay between the organizational dynamics of the molecular components of glutamatergic synapses and synaptic transmission. We demonstrated that a) trafficking of neuronal molecules such as glutamate receptors is highly dynamic, b) regulations of protein-protein interactions play key roles in the control of this trafficking at different steps, including lateral diffusion, endo and exocytosis, c) modulation of glutamate receptor trafficking has a profound impact on synaptic transmission, including on both short and long term post-synaptic plasticity. By combining chemistry, superresolution imaging and physiology, we aim to unravel the dynamics and physical-chemistry of the macro-molecular complexes of the synapse, the nano-scale organization and dynamics of synaptic proteins and membrane trafficking, and the impact of the dynamic of synapse organization on synaptic physiology. Results obtained in these three axes are constantly integrated to provide a global view of glutamatergic synapse physiology, from nano-scale interactions to function.
While early intrinsic factors shape initial neuronal contacts, most fine-scale network wiring is driven by environmental factors and experience. A great challenge for our comprehension of brain development is to identify how different environmentally-driven modulators control the dynamic maturation of neuronal connections and circuit assemblies. The project of the team is to understand how neurotransmitter systems dialogue in the developing brain in order to shape functional networks. We focus our attention on the molecular physiology of glutamatergic (e.g.
NMDA-dependent signaling) and dopaminergic loop and the role of such cross-talk in the developmental encoding of learning and novelty. These fundamental issues will be tackled using a challenging and original set of approaches, including in depth imaging with new probes, gaining insight into the dynamic cross-talk between receptors (e.g. single molecule approach, ensemble measurement, and biochemistry), the synaptic and network physiology (e.g. in vivo
electrophysiology, opto-genetic), and rodent models of early life challenge (e.g. schizophrenia, stress).
Chronic pain relies on maladaptive plasticity that induces neuronal sensitization in dorsal spinal networks. The aim of our project is to shed light on basic mechanisms responsible for cellular, and network dysfunctions in the dorsal spinal cord of rodent models of neuropathic pain. Within FBI, we investigate how GABAB inhibition of calcium-dependent intrinsic properties of dorsal horn neurons is hampered in neuropathic conditions by the association of the receptor with various partner proteins. Those interacting proteins impair GABAB inhibition through specific, distinct molecular mechanisms. To this aim we develop an extensive set of approaches for Correlative Light Electron Microscopy.
The advent of fluorescence microscopy beyond the diffraction limit has opened up huge experimental opportunities to directly image and resolve key physiological signaling events inside single synapses in intact brain tissue, a possibility which was considered a pipedream until recently. Our group is invested in harnessing these exciting technological developments to study synapses in their natural habitat and under realistic conditions, aiming to better understand higher brain function and disorders in terms of the underlying synaptic mechanisms. To this end, we are applying novel superresolution microscopy approaches (STED microscopy), giving us a much more complete and refined view of the dynamic behavior and plasticity of neuronal synapses and their interactions with glia cells inside living brain slices. This approach is complemented by a combination of 2-photon imaging & photoactivation and patch-clamp electrophysiology aided by tools from molecular genetics.
The “Quantitative Imaging of the Cell” team is a R&D team composed of engineers and researchers coming from various disciplines (microscopy, image processing, image visualization and microfluidics). Together, they aim to develop novel imaging techniques to better understand the living cell activity at high spatial and temporal resolutions, in a high throughput context. The team works in close collaboration with industrial partners (Roper Scientific, Imagine Optics, Nikon, Physik Instrumente, Cytoo, and Molecular Devices). Three main research area are investigated:
-Novel instruments for high-resolution microscopy of living samples, focusing on the development of new instruments for Single Molecule Tracking by Photo-Activation Localization Microscopy (SPTPALM), Local Photoperturbation Microscopy (FRAP/PA), 3D imaging of thick biological specimens (Multi-photon Imaging) and Structure Illumination microscopy (SIM, Compress Sensing).
-Analytical tools for object segmentation, tracking and visualization using CPU and GPU.
-High Content Screening Microscopy to quantify the dynamics of active proteins within living cells, using super-resolution microscopy and micropatterning/microfluidics to control cell geometry and their local chemical environment.
Our aim is to understand the role of adhesion proteins and the actin cytoskeleton in the assembly and turnover of multi-molecular complexes at cell-cell and cell-extracellular matrix contacts. To this aim, we are using a combination of bio-mimetic physico-chemical assays to establish spatiallycontrolled and molecularly-specific adhesive contacts, and high resolution microscopy imaging to probe in real time the dynamics of these multi-protein complexes. We are developing four specific axes:
1.Assembly of macromolecular synaptic complexes triggered by neurexin/neuroligin adhesion
2.Adhesion and actin dynamics in growth cone steering and dendritic spine shape
3.Integrin-dependent adhesion and actin dynamics in migrating cells
4.New imaging methods to probe ligand binding and receptors dynamics in membranes