Allele-Specific Silencing Agents Targeting HTT Polymorphisms
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Solution Overview
Problem
Current methods for treating Huntington's disease, such as antisense oligonucleotide and RNA interference technologies, face challenges in effectively targeting the expanded CAG repeats in the Huntingtin gene due to their size and repetitive nature, requiring detailed knowledge of specific polymorphisms for allele-specific silencing.
Innovation Solution
A method involving the use of nucleic acid silencing agents that target differentiating polymorphisms in the Huntingtin gene, specifically single nucleotide polymorphisms (SNPs), to reduce the expression of the mutant huntingtin protein by identifying and selecting oligonucleotides that preferentially target these polymorphisms in RNA encoding the mutant protein.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If antisense oligonucleotide or RNA interference technologies are used to target the expanded CAG repeats in the Huntingtin gene, then mutant huntingtin protein expression can be reduced, but the repetitive and large size of the CAG expansion makes effective targeting difficult
Solution Approach 1:
The invention extracts the targeting challenge from the repetitive CAG repeat region and relocates it to flanking sequences that contain unique polymorphic sites. By designing silencing agents to target these flanking regions rather than the repetitive repeats themselves, the patent overcomes the difficulty of effectively targeting expanded repeats while maintaining allele-specific specificity.
Solution Approach 2:
The invention introduces flanking sequences as intermediaries between the targeting agent and the CAG repeat region. These flanking sequences contain polymorphic sites that serve as accessible targets for nucleic acid silencing agents, while still enabling allele-specific reduction of mutant huntingtin expression through their linkage to the expanded repeat region.
2Reliability
If constitutive knockout of the HTT gene is performed, then mutant huntingtin expression is eliminated, but it causes lethality during embryonic development
Solution Approach 1:
The invention applies local quality by making the HTT gene silencing allele-specific rather than universal. By designing silencing agents that target polymorphic sites unique to the mutant allele, the patent achieves complete elimination of mutant huntingtin protein while preserving wildtype HTT expression, thereby avoiding embryonic lethality.
Solution Approach 2:
Instead of attempting to silence both alleles and then try to rescue the wildtype function, the invention inverts the approach by designing silencing agents that specifically target only the mutant allele through polymorphic sites. This inversion of the silencing strategy allows selective elimination of mutant protein while maintaining necessary wildtype function.
3Ease of manufacture
If allele-specific silencing is attempted without knowledge of specific polymorphisms, then the approach is simpler, but it cannot achieve effective targeting of the mutant allele
Solution Approach 1:
The invention performs preliminary action by first identifying and characterizing polymorphic sites in the flanking sequences of the HTT gene before designing silencing agents. This preliminary genetic characterization enables the development of allele-specific silencing strategies that are both effective and can be systematically applied to different patients based on their genetic profiles.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for a significant reduction in mutant huntingtin protein expression, potentially offering a therapeutic option for Huntington's disease by maximizing patient coverage with a minimum number of targets, as demonstrated by the association of specific SNPs with CAG-expanded chromosomes.
Implementation Method 1
RNA interference (RNAi) technology, microRNA (miRNA) or small hairpin interference RNA (shRNA), may be used for precise targeting of genes or nucleic-acid gene products
Implementation Method 2
Some antisense (ASO), siRNA and ribozyme molecules have been developed that reduce huntingtin expression in vitro or in mouse models
Data Source
AI summary
Methods and compositions for reducing expression of a mutant huntingtin (mHTT) protein in a cell are provided. Such methods include contacting the cell with an effective amount of a nucleic acid silencing agent targeting a differentiating polymorphism in RNA encoding the mHTT.