DDX3X overexpression decreases dipeptide repeat proteins in a mouse model of C9ORF72-ALS/FTD

Exp Neurol. 2024 Jun:376:114768. doi: 10.1016/j.expneurol.2024.114768. Epub 2024 Mar 29.


Hexanucleotide repeat expansion in C9ORF72 (C9) is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). One of the proposed pathogenic mechanisms is the neurotoxicity arising from dipeptide repeat (DPR) proteins produced by repeat-associated non-AUG (RAN) translation. Therefore, reducing DPR levels emerges as a potential therapeutic strategy for C9ORF72-ALS/FTD. We previously identified an RNA helicase, DEAD-box helicase 3 X-linked (DDX3X), modulates RAN translation. DDX3X overexpression decreases poly-GP accumulation in C9ORF72-ALS/FTD patient-derived induced pluripotent stem cell (iPSC)-differentiated neurons (iPSNs) and reduces the glutamate-induced neurotoxicity. In this study, we examined the in vivo efficacy of DDX3X overexpression using a mouse model. We expressed exogenous DDX3X or GFP in the central nervous system (CNS) of the C9-500 ALS/FTD BAC transgenic or non-transgenic control mice using adeno-associated virus serotype 9 (AAV9). The DPR levels were significantly reduced in the brains of DDX3X-expressing C9-BAC mice compared to the GFP control even twelve months after virus delivery. Additionally, p62 aggregation was also decreased. No neuronal loss or neuroinflammatory response were detected in the DDX3X overexpressing C9-BAC mice. This work demonstrates that DDX3X overexpression effectively reduces DPR levels in vivo without provoking neuroinflammation or neurotoxicity, suggesting the potential of increasing DDX3X expression as a therapeutic strategy for C9ORF72-ALS/FTD.

Keywords: ALS; C9ORF72; FTD; Repeat expansion.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, N.I.H., Extramural

MeSH terms

  • Amyotrophic Lateral Sclerosis* / genetics
  • Amyotrophic Lateral Sclerosis* / metabolism
  • Amyotrophic Lateral Sclerosis* / pathology
  • Animals
  • C9orf72 Protein* / genetics
  • C9orf72 Protein* / metabolism
  • DEAD-box RNA Helicases* / genetics
  • DEAD-box RNA Helicases* / metabolism
  • DNA Repeat Expansion / genetics
  • Dipeptides / metabolism
  • Disease Models, Animal*
  • Frontotemporal Dementia* / genetics
  • Frontotemporal Dementia* / metabolism
  • Frontotemporal Dementia* / pathology
  • Humans
  • Male
  • Mice
  • Mice, Transgenic*


  • DEAD-box RNA Helicases
  • C9orf72 Protein
  • Ddx3x protein, mouse
  • Dipeptides