# microRNA-Regulated Mechanisms Essential for Structural Plasticity of Drosophila Glutamatergic Synapses

> **NIH NIH R01** · HARVARD MEDICAL SCHOOL · 2024 · $511,701

## Abstract

PROJECT SUMMARY / ABSTRACT
 The molecular and cellular mechanisms underlying plasticity of excitatory synapses have fascinated
biologists for many decades. In addition to the importance of these processes in the acquisition and storage of
memories, as well as other adaptations of neural circuits to sensory input or other changing conditions, many of
the effector genes that participate in such mechanisms have recently been associated with a wide range of
neurological, psychiatric and other disorders of the human nervous system. Thus, it is little surprise that synapse
formation, plasticity and structural remodeling are under tight control at many levels. To better understand this,
we have investigated small, non-coding microRNA genes that serve as versatile yet selective regulators of
dynamic gene expression changes that underly the morphological plasticity of the synapse. Through multiple
rounds of genetic tool development, screening, and tissue-specific analysis, we have identified several highly
conserved microRNAs that are required in the postsynaptic cell to allow coordinated remodeling of the synapse
in response to acute stimulation. Because each microRNA controls the expression of specific target mRNAs, our
studies have led us to several key proteins whose expression must be downregulated to allow synapse
remodeling. In particular, our unpublished analysis of miR-219 suggests that it controls expression of a guanine
nucleotide exchange factor (GEF) specific to the Ral GTPase. Although this Ras-independent GEF (dRalGPS)
is very highly conserved, there are no peer reviewed publications on the Drosophila ortholog. Moreover, while
fly miR-219 is perfectly conserved with human miR-219a, and the miR-219 response element (MRE) in RalGPS
is also conserved across species, this relationship has escaped study by other labs. Prior work on Ral at the
Drosophila larval neuromuscular junction (NMJ) delineated a pathway that mediates morphogenesis the
subsynaptic reticulum (SSR) by recruiting Sec5 and other Exocyst components in response to neural activity.
Analysis of our unpublished null mutation, expression transgenes, and antibodies against dRalGPS show that,
like Ral, this Ral GEF is both necessary and sufficient to control the postsynaptic recruitment of key determinants
of SSR structure. However, our biochemical isolation of protein complexes and subsequent genetic analysis of
RalGPS-associated factors suggests that RalGPS may mediate several biological outputs in addition to sec5.
Moreover, biochemical isolation of Argonaut 1 complexes suggests that miR-219 loading into miRISC is activity-
dependent, implicating this cytoskeletal effector pathway is part of an acute synapse plasticity mechanism yet to
be studied in our system. We propose to rigorously test this model with a combination of site-directed
mutagenesis and tissue-specific analysis (Aim 1), genetic epistasis and protein localization studies (Aim 2), and
thorough regulatory analysis of th...

## Key facts

- **NIH application ID:** 10935973
- **Project number:** 5R01NS135403-02
- **Recipient organization:** HARVARD MEDICAL SCHOOL
- **Principal Investigator:** David L. Van Vactor
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $511,701
- **Award type:** 5
- **Project period:** 2023-09-26 → 2027-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10935973

## Citation

> US National Institutes of Health, RePORTER application 10935973, microRNA-Regulated Mechanisms Essential for Structural Plasticity of Drosophila Glutamatergic Synapses (5R01NS135403-02). Retrieved via AI Analytics 2026-06-16 from https://api.ai-analytics.org/grant/nih/10935973. Licensed CC0.

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