Ultrastructural membrane dynamics of mouse and human cortical synapses

Area of Science:

• Neuroscience
• Cell Biology

Background:

• Understanding synaptic transmission is crucial for neuroscience.
• Previous studies lacked visualization of synaptic vesicle dynamics in live human brain tissue.
• Limitations existed in studying dynamic synaptic processes in intact human samples.

Purpose of the Study:

• To visualize synaptic vesicle dynamics in live human brain tissue.
• To investigate the mechanisms of synaptic vesicle endocytosis in human neurons.
• To compare synaptic endocytosis mechanisms between human and mouse brain slices.

Main Methods:

• Zap-and-freeze time-resolved electron microscopy was employed.
• The method was validated using calcium imaging in acute mouse brain slices.
• Synaptic vesicle endocytosis was induced and analyzed in both mouse and human brain slices.

Main Results:

• Synaptic vesicle endocytosis was successfully induced and visualized in both mouse and human brain slices.
• Clathrin-free endocytic pits were observed near the active zone, consistent with ultrafast endocytosis.
• Dynamin 1xA, a key protein for ultrafast endocytosis, localized to the peripheral active zone in both species.
• Inhibiting dynamin trapped endocytic pits at the active zone periphery.

Conclusions:

• Zap-and-freeze electron microscopy enables high-resolution visualization of synaptic vesicle dynamics in intact human brain tissue.
• A conserved mechanism of clathrin-free, ultrafast endocytosis appears to operate in both human and mouse neurons.
• This approach offers potential for future studies on synaptic membrane trafficking in human neurological conditions.