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Published on: December 26, 2015
CAG-targeting artificial miRNA with reduced off-target risk for efficient lowering of pathogenic polyglutamine
Marianna Pewinska-Kolodziejczak1, Anna Kotowska-Zimmer1, Lukasz Przybyl2
1Department of Genome Engineering, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland.
Insights
Researchers developed a novel artificial microRNA (amiRNA) targeting CAG repeats to treat Huntington's disease (HD). This selective therapy effectively reduced toxic proteins in models and showed promise as a safe treatment for HD and other polyglutamine disorders.
Area of Science:
- Neuroscience
- Genetics
- Molecular Biology
Background:
- Huntington's disease (HD) is a neurodegenerative disorder caused by CAG repeat expansions.
- Somatic CAG expansions are implicated in HD progression, necessitating targeted therapies.
- Current therapeutic strategies face challenges in efficacy, selectivity, and off-target effects.
Purpose of the Study:
- To develop allele-selective artificial microRNA (amiRNA) molecules targeting CAG repeats.
- To assess the efficacy and safety of these amiRNAs in cellular and animal models of HD and other polyglutamine disorders.
- To identify a potent and safe therapeutic candidate for polyglutamine diseases.
Main Methods:
- Designed allele-selective amiRNAs with modified guide strands to reduce off-target activity.
- Tested amiRNA efficacy in cellular models of HD, spinocerebellar ataxias (types 1 and 3), and dentatorubral pallidoluysian atrophy.
- Evaluated the lead candidate (amiR136-13A) in an HD mouse model, including toxicity and transcriptomic profiling in human neural stem cells.
Main Results:
- Engineered amiRNAs effectively downregulated polyglutamine proteins in various disease models.
- The candidate amiR136-13A significantly reduced mutant huntingtin levels in the HD mouse brain without inducing toxicity up to 28 weeks post-administration.
- Transcriptomic analysis showed minimal gene expression changes in human HD neural stem cells treated with amiR136-13A.
- amiR136-13A also reduced levels of the pathogenic HTT1a isoform.
Conclusions:
- Developed potent and allele-selective amiRNAs targeting CAG repeat expansions.
- amiR136-13A demonstrates significant therapeutic potential for Huntington's disease.
- This approach shows promise as a safe and effective treatment for HD and other polyglutamine disorders.
Abstract:
Huntington's disease (HD) is the best-known example of a neurodegenerative disorder caused by the expansion of a glutamine-encoding CAG repeat in the causative gene. Growing evidence indicates that somatic CAG expansions play a key role in disease progression, providing a strong rationale for therapeutic strategies directly targeting the repeat tract. However, achieving sufficient efficacy while maintaining allele selectivity and minimizing off-target effects remains a major challenge. Here, we developed allele-selective, CAG-targeting artificial microRNA (amiRNA) molecules that exhibit significantly reduced off-target risk. This was achieved by introducing specific substitutions at selected positions within the guide strand. These molecules effectively downregulated polyglutamine (polyQ) proteins in cellular models of HD, spinocerebellar ataxias types 1 and 3, and dentatorubral pallidoluysian atrophy. The most promising candidate, amiR136-13A, reduced mutant huntingtin levels in different brain regions of the HD mouse model and did not induce toxicity up to 28 weeks following a single administration of an AAV5 vector. Transcriptomic profiling of human HD neural stem cells treated with amiR136-13A revealed minor changes in gene expression. Moreover, amiR136-13A reduced the level of HTT1a, a short pathogenic isoform of huntingtin. Collectively, these findings identify amiR136-13A as a potent, selective, and safe therapeutic candidate for HD and potentially other polyQ disorders.
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