Expression of the repulsive guidance molecule RGM and it receptor Neogenin after spinal cord injury in sea lamprey

Exp Neurol, 2009 · DOI: 10.1016/j.expneurol.2009.02.011 · Published: June 1, 2009

Spinal Cord Injury Regenerative Medicine Neurology

Simple Explanation

This study investigates the role of repulsive guidance molecule (RGM) and its receptor neogenin in spinal cord regeneration in sea lampreys. Unlike mammals, lampreys can regenerate axons and recover function after spinal cord injury. The study aims to understand why some lamprey neurons regenerate well while others do not. The researchers examined the expression of RGM and neogenin after spinal cord transection using in situ hybridization and quantitative PCR. They found that RGM mRNA was expressed in the spinal cord, particularly in neurons of the lateral gray matter and dorsal cells. Following spinal cord injury, RGM expression was downregulated in neurons near the injury site, while neogenin expression remained unchanged in the brainstem. Neogenin was only detected in 'bad regenerators,' suggesting its potential role in limiting regeneration.

Study Duration

2-4 weeks

Participants

100 larval lampreys

Evidence Level

Not specified

Key Findings

1
RGM mRNA is expressed in the spinal cord of sea lampreys, primarily in neurons of the lateral gray matter and dorsal cells.
2
Following spinal cord transection, RGM mRNA is downregulated in neurons close to the injury site (within 10 mm) at 2 and 4 weeks post-transection.
3
Neogenin mRNA expression is unchanged in the brainstem after spinal cord transection, and it is detected only in 'bad regenerators' among identified reticulospinal neurons.

Research Summary

This study investigates the expression of RGM and its receptor neogenin in the sea lamprey spinal cord after injury. It aims to understand their roles in axon regeneration, which occurs in lampreys but not in mammals. The study found that RGM mRNA is expressed in specific neurons in the spinal cord and is downregulated near the injury site after transection. Reactive microglia upregulate RGM expression transiently after injury. Neogenin expression is limited to poorly regenerating neurons and does not change significantly after spinal cord transection. These findings suggest potential roles for RGM and neogenin in regulating axon regeneration in lampreys.

Practical Implications

Potential therapeutic targets

RGM and neogenin could be potential targets for therapeutic interventions aimed at promoting axon regeneration after spinal cord injury.

Understanding regeneration mechanisms

The study provides insights into the molecular mechanisms underlying successful axon regeneration in lampreys, which could inform strategies for promoting regeneration in mammals.

Role of microglia

The study highlights the complex role of microglia in spinal cord injury and regeneration, suggesting that their RGM expression may influence axonal growth.

Study Limitations

1
The study is conducted in sea lampreys, and the findings may not be directly applicable to mammals.
2
The precise mechanisms by which RGM and neogenin influence axon regeneration require further investigation.
3
The study focuses on mRNA expression, and protein levels and activity may not always correlate with mRNA levels.

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