2026-02-02 フランス国立科学研究センター(CNRS)
- https://www.cnrs.fr/en/press/discovery-key-mechanism-halt-most-common-genetic-form-als
- https://www.science.org/doi/10.1126/science.adv2600
反復RNAを変化させずにRANの翻訳を阻害すると、C9ORF72関連のALSおよびFTD表現型が回復する Blocking RAN translation without altering repeat RNAs rescues C9ORF72-related ALS and FTD phenotypes
Xin Jiang, Laure Schaeffer, Divya Patni, Tommaso Russo, […] , and Clotilde Lagier-Tourenne
Science Published:5 Feb 2026
DOI:https://doi.org/10.1126/science.adv2600
Editor’s summary
The expansion of the hexanucleotide repeat GGGGCC in the noncoding region of the C9ORF72 gene is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Jiang et al. investigated whether the pathological effects were driven by aggregated RNA foci or by the dipeptide repeat proteins (DPRs) translated from the sense– and antisense repeat–containing transcripts (see the Perspective by Arnold and La Spada). Using adeno-associated virus constructs, the authors introduced a CUG codon mutation that disrupted DPR translation while preserving the expression of repeat-containing RNAs in mice, showing that the animals had improved behavioral deficits, reduced neuroinflammation, fewer protein aggregates, and increased neuronal survival. These results support the pathogenic role of DPRs in C9ORF72-related diseases. —Mattia Maroso
Structured Abstract
INTRODUCTION
GGGGCC (G4C2) hexanucleotide repeat expansions within the first intron of the C9ORF72 gene represent the most common genetic cause of both amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), two devastating neurodegenerative disorders. The repeat is bidirectionally transcribed into sense G4C2 and antisense C2G4 repeat–containing RNAs, which are subsequently translated into five dipeptide repeat proteins (DPRs): poly-GA, poly-GP, poly-GR, poly-PA, and poly-PR. Repeat-containing RNAs also accumulate into so-called RNA foci that are proposed to participate in the pathology through sequestration of RNA binding proteins. Disentangling the relative contribution of RNA foci and DPR toxicity is critical for guiding therapeutic strategies yet remains challenging given that DPRs are translated from the repeat-containing RNAs through repeat-associated non-AUG (RAN) translation.
RATIONALE
To efficiently discriminate between repeat RNA and DPR-mediated toxicity, we engineered a single-nucleotide mutation in a CUG codon located upstream of the G4C2 repeat. This near-cognate translation start codon was previously identified as the initiation site predominantly used for the generation of DPRs across all three reading frames from the sense RNAs. By mutating this site from CUG to CCG, we specifically disrupted DPR synthesis while preserving the expression and structure of the repeat-containing RNAs.
RESULTS
A single-nucleotide substitution (CUG→CCG) alleviated translation of DPRs from all three frames (poly-GA, poly-GP, and poly-GR) in two mouse models with adeno-associated virus (AAV)–mediated expression of either 66 or 150 G4C2 repeats. Although the CUG→CCG edit did not alter the expression level and accumulation of G4C2 RNAs into foci, blocking the production of DPRs resulted in a complete rescue of motor and cognitive behavioral deficits. Furthermore, all measured pathological hallmarks of the disease were alleviated in the absence of DPRs, including motor neuron loss, activation of neuronal STING, accumulation of phosphorylated TDP-43 and TBK1, neuroinflammation, and elevated levels of neurofilament light chain (NfL) in plasma.
CRISPR base editing was then used to mutate CUG to CCG in C9ORF72 patient-derived induced pluripotent stem cells (iPSCs). This precise edit significantly reduced the production of DPRs in iPSC-derived neurons, which was sufficient to partially rescue multiple disease-associated cellular phenotypes. C9ORF72 patient-derived neurons demonstrated transcriptomic changes, STING activation, neurite density loss, mislocalization of nuclear pore complex proteins, and survival deficits that were all either partially or entirely restored in CUG-to-CCG edited isogenic neurons.
CONCLUSION
The comprehensive rescue of disease-related phenotypes in both mouse and iPSC-derived neuronal models, despite the persistence of RNA foci, provides compelling evidence that DPRs are the primary drivers of C9ORF72 ALS and FTD pathogenesis. These findings underscore the potential of an alternative therapeutic strategy targeting DPR synthesis rather than reducing C9ORF72 repeat-containing RNAs in ALS and FTD.
DPRs, rather than repeat-containing RNAs, drive C9ORF72 ALS and FTD pathogenesis.
C9ORF72 G4C2 repeat expansions generate RNA foci and DPRs. Editing a CUG translation start codon upstream of the repeat alleviates DPR translation while preserving accumulation of RNA foci. Blocking DPRs improved behavioral, cellular, and molecular outcomes in mouse models and patient iPSC-derived neurons, demonstrating DPRs as key drivers of C9ORF72 disease progression.
Abstract
GGGGCC (G4C2) repeat expansion in C9ORF72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Toxicity is thought to result from the accumulation of either repeat RNAs and/or dipeptide repeat proteins (DPRs) translated from repeat-containing transcripts through repeat-associated non-AUG (RAN) translation. To disentangle RNA from DPR toxicity, we mutated a CUG codon predominantly used to initiate DPR translation from all three reading frames. This mutation disrupted DPR synthesis while preserving the expression of repeat-containing RNAs. Despite the accumulation of RNA foci, behavioral deficits and pathological abnormalities, including p-TDP-43 inclusions, STING activation, motor neuron loss, neuroinflammation, and increased plasma neurofilament concentration, were alleviated in C9ORF72 mice. Base editing of the CUG codon also improved molecular phenotypes and survival in patient induced pluripotent stem cell–derived neurons, which highlights the potential of therapeutically targeting DPR production rather than repeat RNAs.
