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Updated: Jul 14, 2026
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Electrophysiological Investigations of Retinogeniculate and Corticogeniculate Synapse Function
Published on: August 7, 2019
Three-dimensional architecture of presynaptic terminal cytomatrix
Léa Siksou1, Philippe Rostaing, Jean-Pierre Lechaire
1Inserm U789, Ecole Normale Supérieure, 75005 Paris, France.
Summary
The presynaptic cytomatrix forms a dense filament network, interconnecting synaptic vesicles (SVs) and linking them to active zones. This scaffold organizes SVs for rapid calcium-triggered release.
Area of Science:
- Neuroscience
- Cell Biology
- Biophysics
Background:
- Presynaptic terminals mediate rapid synaptic vesicle (SV) fusion after calcium influx.
- The organization of the presynaptic cytomatrix is crucial for regulated SV trafficking and release.
- The precise mechanisms by which the cytomatrix links SVs, maintains them near active zones (AZs), and organizes docked SVs remain unclear.
Purpose of the Study:
- To analyze the three-dimensional (3D) architecture of the presynaptic cytomatrix.
- To understand how the cytomatrix influences synaptic vesicle organization and positioning at release sites.
Main Methods:
- Electron tomography of presynaptic terminals in rat hippocampal CA1 area.
- High-pressure freezing, cryosubstitution, and embedding to preserve cytomatrix structure.
- Immunogold localization of synaptic proteins (synapsin, Bassoon, CAST).
Main Results:
- Synaptic vesicles (SVs) are embedded in a dense filament network, with each vesicle connected to approximately 1.5 neighbors.
- Peripheral SVs are linked to the plasma membrane by longer filaments, more abundant at the active zone (AZ).
- Docked SVs cluster around presynaptic densities at the AZ, with filaments emerging from these densities.
- Synapsin is localized within the presynaptic bouton, while Bassoon and CAST are near the AZ.
- In synapsin triple knock-out mice, SV number decreased significantly, but bouton size and SV-AZ distance remained largely unchanged.
Conclusions:
- The presynaptic molecular scaffold exerts significant morphological constraints on SV organization.
- SVs are tightly interconnected within the axonal bouton, forming a network preferentially connected to the AZ.
- This organized cytomatrix is essential for efficient synaptic transmission.
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