G₂C₄ targeting antisense oligonucleotides potently mitigate TDP-43 dysfunction in human C9orf72 ALS/FTD induced...

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• The C9orf72 G₄C₂ repeat expansion is a leading genetic cause of Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal Dementia (FTD).
• Dipeptide repeat proteins are implicated in toxicity, but the role of repeat RNA, especially antisense repeat RNA, remains understudied.
• Recent clinical trials targeting sense G₄C₂ repeat RNA failed, despite reducing protein levels.

Purpose of the Study:

• To investigate the toxicity of antisense G₂C₄ repeat RNA in C9orf72 ALS/FTD.
• To evaluate the therapeutic potential of targeting G₂C₄ antisense repeat RNA.
• To explore reasons for the failure of previous G₄C₂ sense-targeting clinical trials.

Main Methods:

• Utilized induced pluripotent stem cell (iPSC)-derived neurons (iPSNs) from healthy individuals and C9orf72 ALS/FTD patients.
• Assessed TDP-43 dysfunction induced by sense (G₄C₂) and antisense (G₂C₄) repeat RNA.
• Administered antisense oligonucleotides (ASOs) targeting either G₄C₂ sense or G₂C₄ antisense repeat RNA.

Main Results:

• G₂C₄ antisense repeat RNA, but not G₄C₂ sense repeat RNA, was sufficient to induce TDP-43 dysfunction in iPSNs.
• Targeting G₂C₄ antisense repeat RNA with ASOs, but not G₄C₂ sense repeat RNA, mitigated TDP-43 dysfunction deficits in patient-derived iPSNs.
• These findings contrast with the expected outcomes based on targeting sense repeat RNA.

Conclusions:

• Antisense G₂C₄ repeat RNA is a key driver of TDP-43 dysfunction in C9orf72 ALS/FTD.
• G₂C₄ antisense repeat RNA represents a potential therapeutic target for ALS and FTD.
• The toxicity of antisense repeat RNA may explain the failure of prior clinical trials targeting sense repeat RNA.