A new center for interdisciplinary research in Neuroscience

Discern the infinitely small in order to grasp the complexity of the brain The Institute for Interdisciplinary Neuroscience (IINS - UMR 5297) is a new research center that has officially opened its doors January 1st, 2011. The IINS is part of the "Centre National de la Recherche Scientifique" & the "Université Bordeaux Segalen". The IINS unite researchers with diverse areas of expertise, and create a highly synergistic environment to promote: > The development of innovative methods and investigation tools, especially those based on molecular biology, physiology, optics, chemistry, physics and computer science. > The application of such tools to push the boundaries of the study of molecular events underlying the activity of the brain. This will include studying the morpho-dynamic and functional properties of the nervous system to understand the complexity of its molecular assemblies and functions at an integrated level. > The development of the Bordeaux Imaging Center, a core facility of service, training and R & D in cellular imaging of international stature to permit the transfer to the scientific community and industry of the tools developed in IINS.

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Unified quantitative model of AMPA receptor trafficking at synapses - PNAS, February 13, 2012

In PNAS, Olivier Thoumine and colleagues describe a computer model incorporating the two main mechanisms that regulate AMPA receptor trafficking at excitatory synapses: membrane diffusion and vesicular trafficking.
See the abstract and a video presentation of this work at the following link (here).

Individual AMPAR trajectory:
Example of a simulated AMPAR trajectory (red line), in a 2 x 6 µm region containing 3 synapses.
The trajectory lasts 50 sec. Note the high diffusion in the extrasynaptic space (black), the slow diffusion
in synapses (green), and the reversible trapping in the PSDs (blue). Synapses are separated by 2 µm.

February 2012 - By Hélène ROUQUETTE-VALEINS | Link to the page (French)

From La Rochelle to Bordeaux, the saga of Explora Nova

Three offices on the second floor of the Functional Genomics Centre

Explora Nova inaugurated Friday, February 10, 2012, its new installation on the ongoing site of Neurocampus Bordeaux. It asserts the extension of the company, moving from La Rochelle to be closer of the Labex Brain directed by the neurobiologist Daniel Choquet.
Head of the Interdisciplinary Institute of Neuroscience (IINS), Daniel Choquet has worked hard to allow the installation of this Research and Development company in Aquitaine.

Explora Nova designs systems for image analysis, stereology and automatic microscopy for scientific research and industrial quality control. Christophe Ranger, one of its creators, has presented three facilities achieved through a partnership with Zeiss: an upright microscope, a reversed microscope allowing the study of living cells, and an electrophysiological microscope.

Scientific excellence for tomorrow's medecine:
Daniel Choquet, laureate of the "Victoires de la médecine 2011" as head of the excellence cluster BRAIN*

 
It is within the walls of the prestigious University of Paris Descartes that took place on Saturday November 26^th, the ceremony of Victories in medicine 2011. Ten medical teams and scientists selected as part of Investments for the Future were distinguished for their scientific and technological potential for therapeutic innovation. Daniel Choquet, director of the Laboratory of Excellence BRAIN, was honored for the project whose main aim is to bring together the skills and multidisciplinary approaches, optimize neuroscience research in Bordeaux in order to improve treatment of neurological diseases.  

Two-Color STED Microscopy of Living Synapses Using A Single Laser-Beam Pair 

November 2011 issue of Biophysical Journal  

Jan Tønnesen, Fabien Nadrigny, Katrin I. Willig, Roland  Wedlich-Söldner and U. Valentin Nägerl

Abstract

The advent of superresolution microscopy has opened up new research opportunities into dynamic processes at the nanoscale inside living biological specimens. This is particularly true for synapses, which are very small, highly dynamic, and embedded in brain tissue. Stimulated emission depletion (STED) microscopy, a recently developed laser-scanning technique, has been shown to be well suited for imaging living synapses in brain slices using yellow fluorescent protein as a single label. However, it would be highly desirable to be able to image presynaptic boutons and postsynaptic spines, which together form synapses, using two different fluorophores. As STED microscopy uses separate laser beams for fluorescence excitation and quenching, incorporation of multicolor imaging for STED is more difficult than for conventional light microscopy. Although two-color schemes exist for STED microscopy, these approaches have several drawbacks due to their complexity, cost, and incompatibility with common labeling strategies and fluorophores.

Therefore, we set out to develop a straightforward method for two-color STED microscopy that permits the use of popular green-yellow fluorescent labels such as green fluorescent protein, yellow fluorescent protein, Alexa Fluor 488, and calcein green. Our new (to our knowledge) method is based on a single-excitation/STED laser-beam pair to simultaneously excite and quench pairs of these fluorophores, whose signals can be separated by spectral detection and linear unmixing. We illustrate the potential of this approach by two-color superresolution time-lapse imaging of axonal boutons and dendritic spines in living organotypic brain slices.

Link of the publisher:

http://www.cell.com/biophysj/fulltext/S0006-3495%2811%2901200-8

In Vivo Imaging of Inter-Synaptic Vesicle Exchange Using VGLUT1Venus Knock-In Mice - October 2011 issue of The Journal of Neuroscience

Abstract

The vesicular glutamate transporter VGLUT1 loads synaptic vesicles with the neurotransmitter glutamate and thereby determines glutamate release at many synapses in the mammalian brain. Due to its function and selective localization, VGLUT1 is one of the most specific markers for glutamatergic synaptic vesicles. It has been used widely to identify glutamatergic synapses, and its expression levels are tightly correlated with changes in quantal size, modulations of synaptic plasticity, and corresponding behaviors. We generated a fluorescent VGLUT1Venus knock-in mouse for the analysis of VGLUT1 and glutamatergic synaptic vesicle trafficking. The mutation does not affect glutamatergic synapse function, and thus the new mouse model represents a universal tool for the analysis of glutamatergic transmitter systems in the forebrain. Previous studies demonstrated synaptic vesicle exchange between terminals in vitro. Using the VGLUT1Venus knock-in, we show that synaptic vesicles are dynamically shared among boutons in the cortex of mice in vivo. We provide a detailed analysis of synaptic vesicle sharing in vitro, and show that network homeostasis leads to dynamic scaling of synaptic VGLUT1 levels.

STED Nanoscopy of Actin Dynamics in Synapses Deep Inside Living Brain Slices

September 2011 issue of  Biophysical Journal

Nicolai T. Urban, Katrin I. Willig, Stefan W. Hell and U. Valentin Nägerl

Abstract

It is difficult to investigate the mechanisms that mediate long-term changes in synapse function because synapses are small and deeply embedded inside brain tissue. Although recent fluorescence nanoscopy techniques afford improved resolution, they have so far been restricted to dissociated cells or tissue surfaces. However, to study synapses under realistic conditions, one must image several cell layers deep inside more-intact, three-dimensional preparations that exhibit strong light scattering, such as brain slices or brains in vivo.

Using aberration-reducing optics, we demonstrate that it is possible to achieve stimulated emission depletion superresolution imaging deep inside scattering biological tissue. To illustrate the power of this novel approach, we resolved distinct distributions of actin inside dendrites and spines with a resolution of 60–80 nm in living organotypic brain slices at depths up to 120 micrometers. In addition, time-lapse stimulated emission depletion imaging revealed changes in actin-based structures inside spines and spine necks, and showed that these dynamics can be modulated by neuronal activity.
Our approach greatly facilitates investigations of actin dynamics at the nanoscale within functionally intact brain tissue.

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Endocytosis of the glutamate receptor subunit GluK3 controls polarized trafficking

Abstract

Kainate receptors (KARs) are widely expressed in the brain and are present both at pre- and postsynaptic sites. GluK3-containing KARs are thought to compose presynaptic autoreceptors that facilitate hippocampal mossy fiber synaptic transmission. Here we identify molecular mechanisms that underlie the polarized trafficking of KARs composed of the GluK3b splice variant. Endocytosis followed by degradation is driven by a di-leucine motif on the cytoplasmic C-terminal domain of GluK3b in heterologous cells, in cultured hippocampal neurons and in dentate granule cells from organotypic slice cultures. The internalization of GluK3b is clathrin and dynamin2-dependent. GluK3b is differentially endocytosed in dendrites as compared to the axons. These data suggest that the polarized trafficking of KARs in neurons could be controlled by the regulation of receptor endocytosis.

Figure: Mutation of the di-leucine motif of GluK3b in di-valine directs the kainate receptors to the axon. GluK3bVV is detected in the axon whereas GluK3b is completely excluded from this compartment.