Silencing of genes responsible for polyQ diseases using chemically modified single-stranded siRNAs

Area of Science:

• Genetics
• Molecular Biology
• Neuroscience

Background:

• Polyglutamine (polyQ) diseases are a group of nine genetic disorders caused by expanded CAG triplet repeats encoding glutamine.
• Oligonucleotide (ON)-based therapies, particularly targeting the CAG repeat, show promise for selective silencing of mutant alleles.
• Existing CAG repeat-targeting miRNA-like siRNAs achieve specific inhibition via mismatches with the target site.

Purpose of the Study:

• To design novel single-stranded siRNAs with base substitutions and chemical modifications for improved, universal polyQ disease therapeutics.
• To evaluate the efficacy of these modified ONs in cellular models of Huntington's disease (HD), spinocerebellar ataxia type 3 (SCA3), and dentatorubral-pallidoluysian atrophy (DRPLA).

Main Methods:

• Design and synthesis of novel single-stranded siRNAs incorporating base substitutions and chemical modifications (e.g., 2'-fluoro).
• Testing of these ONs in cellular models of HD, SCA3, and DRPLA, including cultured human fibroblasts and HD mouse striatal cells.
• Assessment of the selective downregulation of mutant huntingtin, ataxin-3, and atrophin-1 levels.

Main Results:

• Selected novel siRNAs demonstrated efficient and selective downregulation of mutant huntingtin, ataxin-3, and atrophin-1 in human fibroblasts.
• The efficacy of these modified ONs, particularly those with 2'-fluoro modifications, was confirmed in HD mouse striatal cells.
• The designed siRNAs show potential for broad applicability across multiple polyQ diseases.

Conclusions:

• Novel single-stranded siRNAs with specific base substitutions and chemical modifications are effective therapeutic tools for polyQ diseases.
• These modified ONs achieve selective silencing of mutant alleles in cellular models of HD, SCA3, and DRPLA.
• The developed siRNA strategy offers a promising avenue for universal treatment of various polyglutamine disorders.