High-Fidelity Cas9 Editing for Beta-Globin Mutation Correction
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Solution Overview
Problem
Current methods for managing hemoglobinopathies like sickle cell disease are inadequate, with gene therapy being investigational and hematopoietic stem cell transplantation carrying risks and requiring matched donors, highlighting a need for improved therapeutic approaches.
Innovation Solution
A method involving homology-directed repair (HDR) using a high-fidelity S. pyogenes Cas9 endonuclease, single guide RNA, and recombinant vectors to correct the E6V mutation in the HBB gene, reducing off-target cleavage and enhancing repair efficiency with inhibitors like 53BP1 and DNA-PK inhibitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard Cas9 endonuclease is used for gene editing, then gene editing capability is achieved, but off-target cleavage occurs reducing safety
Solution Approach 1:
The patent modifies the Cas9 endonuclease by introducing point mutations (e.g., D10A, H840A, H841A) to create a dead Cas9 (dCas9) or nickase variant that reduces off-target cleavage activity while maintaining on-target binding capability. This parameter change in the enzyme's catalytic activity resolves the contradiction between achieving gene editing and avoiding off-target effects
Solution Approach 2:
The patent uses a single-guide RNA (sgRNA) as an intermediary that directs the Cas9 endonuclease to specific target sequences. The sgRNA provides sequence specificity that enhances on-target editing while the modified Cas9 reduces off-target cleavage, together resolving the safety-accuracy contradiction
2Reliability
If homology-directed repair is enhanced for mutation correction, then treatment efficacy improves, but repair pathway complexity increases
Solution Approach 1:
The patent introduces a donor DNA template with the desired correction sequence before inducing the double-strand break. This preliminary action provides the template for homology-directed repair, ensuring that when the break is repaired, the correct sequence is restored without requiring complex cellular machinery to generate the correction de novo
Solution Approach 2:
The patent uses a donor DNA template that serves as a copy of the correct HBB gene sequence. This template is used by the cell's homology-directed repair machinery to copy the correct sequence into the mutated gene, simplifying the repair process by providing a ready-made template rather than requiring complex error-correction mechanisms
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 effectively corrects the E6V mutation in human beta-globin genes, potentially treating sickle cell disease by reducing off-target effects and improving HDR efficiency, offering a safer and more accessible therapeutic option.
Implementation Method 1
homology directed repair (HDR) of a double-strand break (DSB) in a target region in a human beta-globin (HBB) gene
Implementation Method 2
a S. pyogenes Cas9 endonuclease, an mRNA encoding the S. pyogenes Cas9 endonuclease, or a recombinant expression vector comprising a nucleotide sequence encoding the S. pyogenes Cas9 endonuclease, wherein the S. pyogenes Cas9 endonuclease is a high fidelity Cas9
Data Source
AI summary
The disclosure features methods of correcting a mutation in the human beta-globin (HBB) gene in a cell or population of cells. The disclosure also features methods of increasing repair of a DNA double stranded break (DSB) in an HBB gene by the homology-directed repair (HDR) pathway. The disclosure also features compositions for use in the methods.