Allele-specific silencing of mutant huntingtin and ataxin-3 genes by targeting expanded CAG repeats in mRNAs

Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA.
Nature Biotechnology (Impact Factor: 41.51). 06/2009; 27(5):478-84. DOI: 10.1038/nbt.1539
Source: PubMed


Expanded trinucleotide repeats cause many neurological diseases. These include Machado-Joseph disease (MJD) and Huntington's disease (HD), which are caused by expanded CAG repeats within an allele of the ataxin-3 (ATXN3) and huntingtin (HTT) genes, respectively. Silencing expression of these genes is a promising therapeutic strategy, but indiscriminate inhibition of both the mutant and wild-type alleles may lead to toxicity, and allele-specific approaches have required polymorphisms that differ among individuals. We report that peptide nucleic acid and locked nucleic acid antisense oligomers that target CAG repeats can preferentially inhibit mutant ataxin-3 and HTT protein expression in cultured cells. Duplex RNAs were less selective than single-stranded oligomers. The activity of the peptide nucleic acids does not involve inhibition of transcription, and differences in mRNA secondary structure or the number of oligomer binding sites may be important. Antisense oligomers that discriminate between wild-type and mutant genes on the basis of repeat length may offer new options for developing treatments for MJD, HD and related hereditary diseases.

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Available from: David Reid Corey, Sep 02, 2014
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    • "Different approaches have been employed to achieve allele-specific silencing of mHTT by targeting disease-linked polymorphisms, including the CAG expansion [26]–[28], a CAG expansion-associated deletion [29], and single nucleotide polymorphisms (SNPs) enriched on HD alleles (HD-SNPs) [30]–[34]. Several CAG repeat-targeting silencing reagents are under pre-clinical development and have shown great promise when tested in cells from juvenile HD patients [28], [35]–[38], whom display a more severe form of the disease with onset before the age of 20 [39]. "
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    ABSTRACT: Huntington disease (HD) is an inherited, fatal neurodegenerative disorder caused by a CAG repeat expansion in the huntingtin gene. The mutant protein causes neuronal dysfunction and degeneration resulting in motor dysfunction, cognitive decline, and psychiatric disturbances. Currently, there is no disease altering treatment, and symptomatic therapy has limited benefit. The pathogenesis of HD is complicated and multiple pathways are compromised. Addressing the problem at its genetic root by suppressing mutant huntingtin expression is a promising therapeutic strategy for HD. We have developed and evaluated antisense oligonucleotides (ASOs) targeting single nucleotide polymorphisms that are significantly enriched on HD alleles (HD-SNPs). We describe our structure-activity relationship studies for ASO design and find that adjusting the SNP position within the gap, chemical modifications of the wings, and shortening the unmodified gap are critical for potent, specific, and well tolerated silencing of mutant huntingtin. Finally, we show that using two distinct ASO drugs targeting the two allelic variants of an HD-SNP could provide a therapeutic option for all persons with HD; allele-specifically for roughly half, and non-specifically for the remainder.
    Full-text · Article · Sep 2014 · PLoS ONE
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    • "Several other diseases are caused by similar molecular mechanism of expanded polyglutamine repeats. One ASO prototype against the polyglutamine repeats, discriminates between wild-type and mutant genes on the basis of repeat length and offers a therapy by repressing expanded CAG tract in spinocerebellar ataxia 1, in spinocerebellar ataxia 3/ Machado-Joseph disease and in dentatorubral–pallidoluysian atrophy (Evers et al., 2011; Hu et al., 2009). "
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    ABSTRACT: Molecular genetics insight into the pathogenesis of several neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, Huntington's disease and amyotrophic lateral sclerosis, encourage direct interference with the activity of neurotoxic genes or the molecular activation of neuroprotective pathways. Oligonucleotide-based therapies are recently emerging as an efficient strategy for drug development and these can be employed as new treatments of neurodegenerative states. Here we review advances in this field in recent years which suggest an encouraging assessment that oligonucleotide technologies for targeting of RNAs will enable the development of new therapies and will contribute to preservation of brain integrity.
    Full-text · Article · Apr 2014 · Brain research
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    • "Other potential therapeutic strategies in polyQ diseases, are based on the use of several types of modified single stranded ASOs that target the CAG expansion in the mutant HTT or ATXN3 mRNA, while preserving the normal function of the wild type allele (Hu et al., 2009a,b,c; Gagnon et al., 2010; Fiszer et al., 2012; Yu et al., 2012). The longer CAG track in the mutant allele offers more binding sites for the complementary ASOs (Figure 4). "
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    ABSTRACT: Trinucleotide-repeat expansion diseases (TREDs) are a group of inherited human genetic disorders normally involving late-onset neurological/neurodegenerative affectation. Trinucleotide-repeat expansions occur in coding and non-coding regions of unique genes that typically result in protein and RNA toxic gain of function, respectively. In polyglutamine (polyQ) disorders caused by an expanded CAG repeat in the coding region of specific genes, neuronal dysfunction has been traditionally linked to the long polyQ stretch. However, a number of evidences suggest a detrimental role of the expanded/mutant mRNA, which may contribute to cell function impairment. In this review we describe the mechanisms of RNA-induced toxicity in TREDs with special focus in small-non-coding RNA pathogenic mechanisms and we summarize and comment on translational approaches targeting the expanded trinucleotide-repeat for disease modifying therapies.
    Full-text · Article · Dec 2013 · Frontiers in Molecular Neuroscience
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