Allele-selective inhibition of mutant huntingtin expression with antisense oligonucleotides targeting the expanded...

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• Huntington's disease (HD) is a fatal neurodegenerative disorder caused by a CAG trinucleotide repeat expansion in the huntingtin (HTT) gene.
• Current therapeutic strategies aim to selectively reduce mutant HTT expression while preserving normal HTT function.

Purpose of the Study:

• To evaluate antisense oligonucleotides (ASOs) designed to target the expanded CAG repeat in HTT mRNA for selective inhibition of mutant HTT protein expression.
• To assess the allele selectivity and mechanism of action of these ASOs in cellular models of HD.

Main Methods:

• Development and testing of various ASOs with modifications like bridged nucleic acids and phosphorothioate linkages.
• Evaluation of ASO efficacy and selectivity in patient-derived fibroblasts and cell lines with varying CAG repeat lengths.
• In vitro studies to investigate ASO binding, HTT mRNA integrity, and ribonuclease H activity.

Main Results:

• Several modified ASOs demonstrated allele-selective silencing of mutant HTT protein expression in patient-derived fibroblasts.
• Selectivity was maintained in cell lines with CAG repeat lengths typical of most HD patients and did not impact other CAG repeat-containing genes.
• ASOs did not degrade HTT mRNA and appeared to inhibit gene expression at the translational level, evidenced by cooperative binding of multiple ASO molecules.

Conclusions:

• ASOs targeting the expanded CAG repeat in HTT mRNA offer a potential therapeutic strategy for Huntington's disease.
• These ASOs exhibit allele selectivity, inhibiting mutant HTT expression while preserving normal HTT function.
• The findings support the development of oligonucleotide-based therapeutics for HD with precise allelic discrimination.