RNA modifications have emerged as key regulators of gene expression, affecting translation, RNA stability and subcellular localization. In recent years, one of the most common RNA modifications, N6-methyladenosine (m6A), has been shown to influence brain development, cognitive functions, and behavior. We will discuss work using Drosophila as a model organism to explore the role of RNA modifications, specifically m6A, in brain development and behavior. We will focus on sex-specific roles for mRNA modifications in regulating developmental and behavioral phenotypes, including stress response and food choice.

MN Flamand1,2

RNA modifications have emerged as a pervasive feature of cellular mRNAs with diverse impacts on gene expression. N⁶-methyladenosine (m⁶A), the most abundant internal mRNA modification, is involved in the control of mRNA processing, stability, and translation and has important roles within the nervous system. Studies in animal models have revealed severe neurodevelopmental and cognitive deficits linked to disruptions in mRNA modification machinery. However, the specific molecular mechanisms through which m⁶A mediates these effects remain poorly defined. We previously found that m⁶A contributes to the localization of select mRNAs to dendrites and axons in mouse hippocampal neurons. We propose that m⁶A readers interact with distinct proteins in both the soma and synapses, thereby locally regulating gene networks crucial for synaptic plasticity. We hypothesize that disruption in these networks cause defects in synaptic function and contribute to the progression of neurodegenerative disorders associated with cognitive impairment. Advancements in this line of research critically rely on a better understanding of the local interactions and functions of RBPs in the brain. However, the tools to identify interactions in neurites harboring functional synapses are lacking. To overcome this obstacle, we are developing proximity labeling methods to map protein-protein and protein-RNA interactions in neuronal projections in vitro and at synapses in vivo. By integrating biochemical assays, transcriptomic analyses, and advanced imaging techniques, we aim to elucidate the complex roles of m⁶A readers at synapses and understand how their functions are altered during neurodegeneration.

1Neuroscience Unit, CHU de Québec Research Centre – Université Laval, 2Department of Psychiatry and Neuroscience, Faculty of Medicine, Université Laval

Circular RNAs (circRNAs) are a class of regulatory RNAs that are enriched in synapses and recently implicated in cognitive processes. Emerging studies have also shown that circRNAs can encode micropeptides, which suggests that there are novel proteoforms in the adult brain awaiting discovery. Here, using a high-throughput IRES reporter screen and ribosome sequencing, together with mass spectrometry on synaptosomes isolated from the medial prefrontal cortex (mPFC) of behaviorally trained male C57/Bl6 mice, we have found widespread local circRNA translation in response to fear extinction learning. More than 1500 synapse-enriched circRNAs contain active IRES elements, with 324 circRNAs interacting with the ribosome, and 241 ribosome-bound circRNAs exhibiting direct evidence of activity-induced translation.Furthermore, we have identified a novel micropeptide (P1) that is derived from a single exon circRNA, the linear mRNA host of which encodes an enzyme involved in protein repair. Although P1 is only a third of the size of the full-length protein, it is locally expressed, enzymatically active, and interacts with plasticity-related synaptic proteins, including CamKIIα. In addition, targeted P1 knockdown impairs, whereas its overexpression enhances fear extinction memory. The discovery of an experience-dependent circRNA-derived micropeptide that is biologically active in the adult brain sheds new light on the ‘dark’ proteome and expands the notion that synapse-enriched circRNAs are key drivers of localized plasticity and memory

Professor Timothy Bredy, Queensland Brain Institute, University of Queensland

Yanhong Shi, Ph.D.

RNA modifications occur in all classes of cellular RNAs and play important roles in important biological processes and pathological events. Increasing studies demonstrate that RNA modifications could have key regulatory roles parallel to those of DNA and protein modifications. The biological relevance of RNA modifications in development and human diseases has been explored extensively in recent years. Our study aims to decipher the functional roles and underlying mechanisms of RNA modification in brain disorders. We will explore how RNA modification impacts the nervous system and dysregulated RNA modification links to brain disorders.

Beckman Research Institute of City of Hope