# Defining the Role of DDX6 in Regulating FUS Condensates

> **NIH NIH F31** · JOHNS HOPKINS UNIVERSITY · 2022 · $46,752

## Abstract

PROJECT SUMMARY
Fused in sarcoma (FUS) is a nuclear RNA binding protein that undergoes liquid-liquid phase separation (LLPS).
When mislocalized and/or dysregulated, aberrant phase separation of FUS leads to the formation of pathogenic
solid-like aggregates that are implicated in neurodegenerative diseases including amyotrophic lateral sclerosis
(ALS) and frontotemporal dementia (FTD). We have recently discovered that reduction of DDX6, an RNA
helicase known to interact with FUS, significantly diminishes cytoplasmic FUS granule formation during stress
in neuroblastoma cells (SH-SY5Y). Our preliminary results show that (i) DDX6 modulates FUS condensate
number and size in a concentration dependent manner in vitro i.e., DDX6 promotes FUS condensate formation
at low concentrations but limits growth above a finite level and (ii) DDX6 forms a discontinuous ring around FUS
condensates. Building on these exciting results, I aim to test the hypothesis that DDX6 regulates FUS
granules through dual roles as a granule nucleator and Pickering agent. Pickering agents are particles with
distinct properties which adsorb to the surface of condensates, promoting their liquidity and maintaining small
condensate size. Based on our results, we propose that DDX6 promotes FUS granule nucleation while its role
as a Pickering agent maintains small droplet size and liquidity, thus preventing pathogenic aggregation.
Additionally, we predict that ATP binding and RNA structure will affect the activity of DDX6 on FUS granules. We
will test these predictions in three aims. Aim 1 will utilize in vitro condensation assays to evaluate the interaction
between DDX6, FUS, RNA and ATP and to establish whether DDX6 acts as a Pickering agent. Aim 2 will utilize
biochemical and single molecule assays to characterize the molecular-level dynamics of the interaction between
FUS, DDX6, and RNA, and its dependence on ATP. Finally, aim 3 will use cell-based methods to investigate
how tuning intracellular DDX6 concentrations and disrupting ATP binding affects FUS granule formation in
wildtype and ALS-associated mutants. Together, this work will lead to a deeper understanding of RNA-protein
granule regulation which is of utmost importance to treating neurodegenerative diseases such as ALS and FTD.

## Key facts

- **NIH application ID:** 10537448
- **Project number:** 1F31GM148067-01
- **Recipient organization:** JOHNS HOPKINS UNIVERSITY
- **Principal Investigator:** Gemechu Mekonnen
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $46,752
- **Award type:** 1
- **Project period:** 2022-08-01 → 2026-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10537448

## Citation

> US National Institutes of Health, RePORTER application 10537448, Defining the Role of DDX6 in Regulating FUS Condensates (1F31GM148067-01). Retrieved via AI Analytics 2026-05-28 from https://api.ai-analytics.org/grant/nih/10537448. Licensed CC0.

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