Presynaptic microtubules: organisation and assembly/disassembly

Area of Science:

• Neuroscience
• Cell Biology
• Microscopy

Background:

• Microtubules are crucial cytoskeletal components in neurons.
• Their precise organization and dynamic behavior in synapses and varicosities are not fully understood.
• Synaptosomes offer a model to study presynaptic structures.

Purpose of the Study:

• To investigate the organization and dynamics of microtubules in central and peripheral axonal synapses and varicosities.
• To examine the assembly and disassembly of microtubules within synaptosomes.
• To explore the functional implications of presynaptic microtubule organization.

Main Methods:

• Electron microscopy was used to examine microtubule organization in synapses and varicosities.
• Synaptosomes were utilized to study microtubule dynamics under various conditions (colchicine, temperature).
• Serial section analysis aided in understanding structural relationships.

Main Results:

• Microtubules are observed in central synapses and autonomic varicosities, often near the active zone.
• In synaptosomes, microtubules form coils apposed to the plasma membrane, associated with mitochondria.
• Presynaptic microtubules in synaptosomes disassemble with colchicine and cold, and reassemble upon warming.

Conclusions:

• Synaptosomes retain the capacity to assemble ordered microtubule coils.
• The number of turns in the microtubule coil may correlate with presynaptic terminal size.
• The study proposes explanations for microtubule scarcity in conventionally prepared synapses.