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Published on: December 9, 2014
Embryonic motor axon development in the severe SMA mouse
Vicki L McGovern1, Tatiana O Gavrilina, Christine E Beattie
1Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, OH 43210, USA.
Human Molecular Genetics
|July 8, 2008
Summary
Spinal muscular atrophy (SMA) research reveals motor neuron axons form normally in SMA mice. However, early denervation and synapse loss occur during embryogenesis, indicating a critical developmental defect.
Area of Science:
- Neuroscience
- Genetics
- Developmental Biology
Background:
- Spinal muscular atrophy (SMA) is a genetic disorder characterized by reduced survival motor neuron (SMN) protein.
- Previous studies in cell cultures and zebrafish models indicated motor neuron axon defects in SMA.
- These defects included reduced growth cone size, axonal length, truncation, and branching.
Purpose of the Study:
- To investigate the effects of SMA on motor neuron development in a mouse model.
- To determine if axonal formation and outgrowth are impaired in SMA mice.
- To identify early morphological defects in SMA motor neurons during embryogenesis.
Main Methods:
- Motor neurons from SMA mice and control littermates were labeled with green fluorescent protein (GFP).
- Axonal development was examined in SMA mice from embryonic day 10.5 to postnatal day 2.
- Synapse occupation by motor axons was assessed in embryonic SMA mice.
Main Results:
- SMA mouse motor axons did not exhibit defects in formation or outgrowth at any developmental stage.
- A significant increase in synapses lacking motor axon input was observed in embryonic SMA mice.
- Early denervation was detected during embryogenesis in severe SMA mice.
Conclusions:
- Motor axon formation and outgrowth are not compromised in severe SMA mouse models.
- The earliest detectable morphological defect in SMA mice is the loss of synapse occupation by motor axons.
- Evidence suggests denervation occurs during embryogenesis in SMA, preceding overt axonal defects.
