The Unexplored Role of Noncoding Regulatory RNAs in Engram Dynamics

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Memory storage involves neuronal ensembles (engrams) identified by activation during encoding and necessity for recall.
• Current methods using immediate-early gene (IEG) expression face limitations due to transcriptional lag, failing to capture real-time neural activity and long-term memory structural changes.

Purpose of the Study:

• To propose the noncoding genome, specifically noncoding RNAs (ncRNAs), as the regulatory infrastructure of engrams.
• To present a 3-phase model of ncRNA regulation in memory formation, maintenance, and consolidation.

Main Methods:

• Review of existing literature on engram cell biology and noncoding RNA functions.
• Proposal of a theoretical framework integrating ncRNA roles across memory phases.

Main Results:

• Synaptic microRNAs act as rapid filters during memory encoding, gating excitability and potentially resolving the IEG latency paradox.
• Long ncRNAs maintain epigenetic identity and valence during the interim memory state.
• Memory consolidation involves ncRNA-driven reactivation of neurogenic and synaptogenic programs, termed "pseudo-developmental" reactivation.

Conclusions:

• ncRNAs are central architects of memory, not accessory molecules.
• The proposed framework unifies understanding of how mature neurons encode diverse experiences.
• ncRNAs are crucial for memory maintenance, specificity, and stability.