MicroRNAs 21 and 199a-3p Regulate Axon Growth Potential through Modulation of Pten and mTor mRNAs

Area of Science:

• Neuroscience
• Molecular Biology
• Regenerative Medicine

Background:

• The mechanistic target of rapamycin (mTOR) pathway enhances axon regeneration by boosting protein synthesis.
• Phosphatase and tensin homolog (PTEN) signaling inhibits mTOR, thus attenuating protein synthesis.
• MicroRNAs (miRs) are implicated in regulating PTEN and mTOR expression, with miR-199a-3p and miR-21 showing altered expression post-spinal cord injury (SCI).

Purpose of the Study:

• To investigate the roles of miR-21 and miR-199a-3p in regulating axon growth in dorsal root ganglion (DRG) and cortical neurons.
• To determine the molecular mechanisms by which these miRs influence neuronal protein synthesis and axon regeneration.

Main Methods:

• Quantitative analysis of miR-21 and miR-199a-3p expression in DRG neurons post-axotomy.
• In vitro studies using cultured adult DRG and embryonic cortical neurons to assess neurite growth.
• miRNA target validation using luciferase assays and mRNA/protein level analysis.
• Overexpression and rescue experiments involving miRNA mimics/inhibitors and modified cDNA constructs.

Main Results:

• miR-21 expression increased, while miR-199a-3p expression decreased in DRG neurons following axotomy.
• miR-21 promoted neurite growth by directly targeting Pten mRNA, decreasing Pten levels and increasing protein synthesis.
• miR-199a-3p attenuated neurite growth by directly targeting mTor mRNA, decreasing mTor levels and protein synthesis.
• The effects of miR-21 and miR-199a-3p on axon growth were dependent on PTEN and mTOR activity, respectively.

Conclusions:

• Injury-induced changes in miR-21 and miR-199a-3p expression modulate axon growth capacity.
• These miRs regulate protein synthesis via the PTEN/mTOR pathway, offering potential therapeutic targets for enhancing neural regeneration after injury.