Blocking somatic repeat expansion and lowering huntingtin via RNA interference synergize to prevent Huntington's...

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• Huntington's disease (HD) is a progressive neurodegenerative disorder lacking approved treatments.
• Somatic expansion of CAG repeats and mutant huntingtin (mHTT) are key drivers of neuronal dysfunction in HD.
• Current HTT-lowering strategies have yielded limited clinical benefits in trials.

Purpose of the Study:

• To evaluate the long-term effects of silencing MSH3, HTT, or both using therapeutic divalent siRNAs in a mouse model of HD.
• To determine if targeting somatic expansion via MSH3 inhibition can ameliorate HD pathology.
• To assess the safety and efficacy of combined MSH3 and HTT silencing for HD treatment.

Main Methods:

• Utilized Q111 HD mice, characterized by significant CAG repeat expansion, mHTT inclusions, and transcriptional dysregulation.
• Administered long-term silencing of MSH3, HTT, or both using RNA interference (RNAi) therapeutics.
• Assessed outcomes including CAG repeat expansion, mHTT inclusion levels, gene expression changes, and potential toxicity in wild-type mice.

Main Results:

• Long-term MSH3 silencing effectively blocked somatic expansion, reduced mHTT inclusions, and reversed gene expression abnormalities in HD mice.
• Single HTT silencing showed minimal impact, whereas combined MSH3/HTT targeting synergistically eliminated inclusions and normalized transcriptomic profiles.
• No observable toxicity was detected in wild-type mice receiving parallel treatment, indicating a favorable safety profile.

Conclusions:

• Somatic expansion represents a viable therapeutic target for Huntington's disease.
• RNAi-based co-silencing of MSH3 and HTT offers a promising disease-modifying strategy for HD.
• Dual targeting of MSH3 and HTT demonstrates synergistic effects and potential for long-term therapeutic intervention in HD.