Super-resolution imaging of neuronal dense-core vesicles

Area of Science:

• Cell Biology
• Microscopy
• Neuroscience

Background:

• Fluorescence microscopy is crucial in biology and medicine but limited by diffraction to ~250 nm resolution.
• Super-resolution techniques like photoactivated localization microscopy (PALM) overcome this, achieving tens of nanometers resolution.
• PALM allows detailed visualization of subcellular structures previously inaccessible.

Purpose of the Study:

• To present a practical protocol for single-color PALM imaging of vesicular structures in fixed neurons.
• To apply this method to study dense-core vesicles (DCVs) in cultured hippocampal neurons.
• To investigate the role of DCV clusters in extrasynaptic trafficking.

Main Methods:

• Labeling cultured neurons with photoconvertible fluorescent proteins targeting vesicle cargo.
• Acquiring sparsely sampled raw image data using a super-resolution microscopy system.
• Processing raw images to reconstruct high-resolution PALM images of vesicles.

Main Results:

• Successfully implemented a single-color PALM protocol for neuronal vesicle imaging.
• Generated exceptionally well-resolved images of dense-core vesicles (DCVs).
• Provided evidence refuting the hypothesis that DCV clusters primarily mediate extrasynaptic trafficking.

Conclusions:

• The developed PALM method is effective for visualizing neuronal vesicles at the nanoscale.
• The findings challenge current models of DCV trafficking, suggesting alternative mechanisms.
• Super-resolution microscopy offers powerful insights into the dynamics and organization of synaptic vesicles.