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Axon branch removal at developing synapses by axosome shedding
Derron L Bishop1, Thomas Misgeld, Mark K Walsh
1Department of Molecular and Cellular and Biology, Harvard University, Cambridge, MA 02138, USA.
Neuron
|November 16, 2004
Summary
Axons are eliminated during nervous system development through a novel cellular mechanism involving Schwann cells engulfing axon tips. These engulfed axon tips form "axosomes," containing synaptic organelles, which may explain other axon loss forms.
Area of Science:
- Neuroscience
- Cell Biology
- Developmental Biology
Background:
- Synapse elimination is crucial for nervous system development.
- Axon loss mechanisms, particularly at the neuromuscular junction, remain largely unknown.
Purpose of the Study:
- To elucidate the cellular mechanisms of axon elimination at the neuromuscular junction.
- To investigate the formation and fate of axonal remnants during synapse elimination.
Main Methods:
- Time-lapse imaging of fluorescently labeled axons.
- Serial electron microscopy to visualize ultrastructural changes.
Main Results:
- Axons are removed via a unique cellular process involving Schwann cells.
- Schwann cells engulf axon tips, forming membrane-bound "axosomes" rich in synaptic organelles.
- The contents of axosomes are integrated into the Schwann cell cytoplasm.
Conclusions:
- Axosome shedding represents a novel mechanism for axon removal during development.
- This process may contribute to other forms of axon loss and glial-axon interactions.