Optimization of Existing RNA Visualization Methods Reveals Novel Dendritic mRNA Dynamics

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Biology

Background:

• Local mRNA translation in dendrites is crucial for synaptic plasticity and neuronal function.
• 3' untranslated regions (UTRs) direct mRNA localization within dendrites.
• Live-cell imaging of dendritic mRNA dynamics is challenging compared to fixed-cell methods like FISH.

Purpose of the Study:

• To optimize RNA visualization techniques for live-cell imaging of dendritic mRNAs.
• To observe novel behaviors and dynamics of mRNAs within neuronal dendrites and synapses.

Main Methods:

• Optimization of MS2-tagging and microinjection of fluorescently-labeled mRNAs for enhanced signal-to-noise ratio (SNR).
• Utilized MS2 coat protein-fluorescent protein (MCP-FP) constructs and specific promoters to improve MS2-tagged mRNA visibility.
• Directly fluorescently labeled mRNAs were employed for brighter granule visualization.

Main Results:

• Significantly improved SNR for MS2-tagged mRNAs through optimized construct ratios and promoter selection.
• Directly labeled mRNAs produced brighter granules, facilitating visualization.
• Dynamic movement of co-labeled mRNA/protein complexes within dendrites and dendritic spines was visualized, including simultaneous movement of three distinct mRNAs and surprising splitting events within spines.

Conclusions:

• Highly optimized RNA-labeling methods enable live-cell visualization of multiple RNA/protein complex dynamics in neurons.
• Newly observed RNA movements in dendrites and synapses offer insights into the complex spatio-temporal control of neuronal gene expression.
• These advancements pave the way for deeper understanding of the molecular mechanisms underlying synaptic plasticity and neuronal function.