Locomotor Training Increases Synaptic Structure With High NGL-2 Expression After Spinal Cord Hemisection

Area of Science:

• Neuroscience
• Spinal Cord Injury Research
• Molecular Biology

Background:

• Previous work showed step training reorganizes neuronal networks in the lumbar spinal cord after hemisection (HX) injury.
• Step training increases excitability of spinally evoked potentials in hindlimb motor neurons.

Purpose of the Study:

• Investigate changes in RNA expression and synapse number in the lumbar spinal cord after thoracic HX injury.
• Determine the effects of post-injury step training on synaptic gene expression and synapse formation.

Main Methods:

• Utilized RNA-Sequencing (RNA-Seq) and immunohistochemistry on rat lumbar spinal cord tissue.
• Analyzed samples 23 days after a mid-thoracic HX injury in trained and untrained groups.

Main Results:

• Gene Ontology (GO) term clustering revealed increased expression of 36 synapse-related genes in trained rats.
• Lrrc4 (NGL-2) was highly expressed in the lumbar spinal cord caudal to the HX lesion in trained rats.
• Trained rats exhibited a greater number of NGL-2/synaptophysin synaptic puncta in the lumbar ventral horn.

Conclusions:

• Findings demonstrate activity-dependent regulation of synapse-related gene expression following HX injury.
• Activity-dependent phenomena may drive epigenetic neuronal group selection for motor learning after SCI.
• Step training facilitates synaptic network reorganization essential for regaining locomotion post-injury.