SaCas9 Dual sgRNA System for DMPK Repeat Excision
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Solution Overview
Problem
Current methods using highly specific nucleases like meganucleases, ZFNs, and TALENs are inefficient for excising trinucleotide repeat expansions in the DMPK gene, particularly for treating myotonic dystrophy, with CRISPR-Cas9 being considered unsuitable for this purpose.
Innovation Solution
The CRISPR-Cas9 system derived from Staphylococcus aureus is used with specific single guide RNAs (sgRNAs) to induce double-strand breaks near nucleotide repeat expansions in the DMPK gene, effectively excising trinucleotide repeat expansions by targeting sequences 5' and 3' to the expansions using a pair of sgRNAs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If highly specific nucleases like meganucleases, ZFNs, and TALENs are used to excise trinucleotide repeat expansions, then sequence-specific targeting is achieved, but excision efficiency is insufficient
Solution Approach 1:
The patent employs a simplified copy of the genomic target sequence in the form of sgRNA, which directs the Cas9 nuclease to the specific trinucleotide repeat expansion site. This sgRNA-Cas9 system achieves both sequence-specific targeting and high excision efficiency, overcoming the limitations of previous nuclease systems that required complex protein-DNA recognition mechanisms.
2Productivity
If CRISPR-Cas9 is used for excising trinucleotide repeat expansions, then excision efficiency is improved, but previous considerations deemed it inappropriate for this purpose
Solution Approach 1:
The patent optimizes key parameters of the CRISPR-Cas9 system including sgRNA design (targeting sequences flanking the trinucleotide repeats), Cas9 delivery methods, and cellular conditions to achieve reliable excision of trinucleotide repeat expansions. These parameter optimizations have transformed CRISPR-Cas9 from a theoretically promising but unproven approach into a reliable and efficient tool for treating myotonic dystrophy.
3Manufacturing precision
If a pair of sgRNAs is used to target sequences 5' and 3' to the nucleotide repeat expansion, then complete excision of the repeat is achieved, but system complexity increases
Solution Approach 1:
The patent divides the targeting task into two separate sgRNAs, each binding to a specific site flanking the trinucleotide repeat expansion (one 5' and one 3'). This segmentation allows precise delimitation of the excision boundaries, ensuring complete removal of the pathological repeat while preserving flanking genomic sequences. The dual sgRNA approach, while adding complexity, provides superior control over excision precision compared to single sgRNA methods.
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 significantly improves the efficiency of excising nucleotide repeat expansions, providing a powerful tool for treating myotonic dystrophy by specifically targeting and removing pathological repeats from the DMPK gene, thereby addressing the limitations of previous technologies.
Implementation Method 1
The sgRNA molecules disclosed herein are able to bind by base-pairing a sequence complementary to a genomic DNA target (protospacer) sequence
Implementation Method 2
The Cas9 endonuclease used herein for excising trinucleotide repeat expansion is derived from Staphylococcus aureus (SaCas9)
Data Source
AI summary
The present invention relates to compositions and methods for the treatment of myotonic dystrophy.