Muscle-Specific Expression Cassettes for Dystrophin Gene Editing
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Solution Overview
Problem
Existing gene therapy approaches for muscular disorders like Duchenne Muscular Dystrophy face challenges in delivering and expressing therapeutic proteins specifically in muscle tissues, particularly skeletal and cardiac muscle, leading to inadequate therapeutic effects.
Innovation Solution
Development of muscle-specific expression cassettes that utilize muscle-specific promoters, enhancers, and post-transcriptional regulatory elements to regulate the expression of engineered nucleases, such as meganucleases, which target and remove specific exons from the dystrophin gene, restoring the reading frame and expressing a modified dystrophin protein.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gene replacement therapy using viral delivery vectors is used to deliver functional dystrophin gene copies, then therapeutic protein expression can be achieved, but delivery efficiency and tissue-specific expression control remain insufficient
Solution Approach 1:
The expression cassette is segmented into distinct functional modules: muscle-specific promoter (MCK or MHC), heterologous protein coding sequence, and polyadenylation signal. This modular design enables independent optimization of each component for muscle-specific expression while simplifying delivery vector construction and improving therapeutic protein expression reliability in target tissues.
Solution Approach 2:
The patent employs muscle-specific promoters (MCK for skeletal muscle, MHC for cardiac muscle) that provide localized gene expression control exclusively in muscle tissues. This ensures therapeutic protein is expressed only where needed, improving delivery efficiency and reducing off-target effects while maintaining reliable therapeutic expression in the intended tissue compartment.
2Reliability
If engineered nucleases are used for gene editing to correct dystrophin gene mutations, then gene expression can be corrected at genomic DNA level, but precise control of nuclease expression in muscle tissue is difficult to achieve
Solution Approach 1:
The engineered nuclease coding sequence is placed under the control of muscle-specific promoters (MCK or MHC), ensuring that nuclease expression is restricted to muscle tissues only. This provides precise spatial control of gene editing activity, enabling reliable correction of dystrophin gene mutations specifically in skeletal or cardiac muscle without affecting other organs, thereby improving both correction reliability and ease of muscle-specific operation.
3Ease of operation
If tissue-specific promoters are used to control heterologous gene expression, then muscle tissue tropism can be achieved, but precise control of expression levels for therapeutically relevant protein amounts is not adequately achieved
Solution Approach 1:
The patent optimizes expression levels by adjusting promoter strength (comparing MCK vs MHC promoters), adding enhancer elements, and modifying polyadenylation signals to maximize therapeutic protein production. These parameter changes maintain muscle-specific tropism while achieving therapeutically relevant expression levels, resolving the contradiction between ease of tissue-specific control and reliability of sufficient protein output.
Solution Approach 2:
The expression cassette combines multiple regulatory elements (muscle-specific promoter, enhancers, polyadenylation signals) into a composite construct that synergistically enhances both muscle-specific expression control and therapeutically relevant protein levels. This composite design achieves precise control of expression levels while maintaining tissue specificity, improving both ease of operation and therapeutic reliability.
4Reliability
If multiple meganucleases are used to excise specific exons from dystrophin coding sequence, then reading frame restoration can be achieved, but complex nuclease expression and coordination is required
Solution Approach 1:
The patent combines multiple meganuclease coding sequences into a single expression cassette under the control of a single muscle-specific promoter, with each nuclease separated by appropriate linkers or 2A self-cleaving peptides. This merged design simplifies delivery vector construction, ensures coordinated expression of all nucleases in muscle tissues, and maintains reliable reading frame restoration while reducing the complexity of managing multiple separate expression systems.
Data Source
AI summary
The present disclosure encompasses nucleic acid expression constructs that regulate the expression of a heterologous protein specifically in muscle tissues (e.g., skeletal muscle and cardiac muscle tissue). In particular embodiments of the disclosure, muscle-specific expression constructs are described that encode a heterologous protein. These heterologous proteins can be any protein that is desired to be expressed in a muscle cell. In particular embodiments of the disclosure, proteins are described for the treatment of Duchenne Muscular Dystrophy (e.g., engineered nucleases such as engineered meganucleases).