RAG2 Gene Correction via CRISPR HDR
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Solution Overview
Problem
Current methods for treating RAG2 deficiencies, such as allogeneic hematopoietic stem cell transplantation, come with complications like graft vs. host disease and incomplete immune reconstitution, and previous gene editing approaches have shown inadequate and dysregulated expression of RAG genes, posing challenges in correcting RAG2 deficiencies effectively.
Innovation Solution
The genetic modification of cells by integrating a functional, codon-optimized RAG2 cDNA at the endogenous RAG2 locus using a CRISPR/Cas9 system, where a single guide RNA targets the RAG2 gene, and a homologous donor template is introduced for homology-directed recombination, allowing expression under the control of the endogenous RAG2 promoter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If allogeneic hematopoietic stem cell transplantation is performed to treat RAG2 deficiency, then immune function can be restored, but graft vs. host disease and transplant-related toxicities occur
Solution Approach 1:
The patent extracts and corrects only the defective RAG2 gene in the patient's own stem cells through targeted gene editing, rather than replacing entire stem cells via transplantation. This removes the harmful alloreactive components while restoring the specific missing function.
Solution Approach 2:
The patient's own hematopoietic stem cells are harvested, genetically corrected ex vivo, and reinfused to restore immune function. This autologous approach eliminates graft vs. host disease by using the patient's self-cells that have been corrected to produce functional RAG2 protein.
2Reliability
If gammaretrovirus- or lentivirus-mediated gene transfer is used to correct RAG deficiency, then RAG gene expression can be introduced, but inadequate and dysregulated expression occurs
Solution Approach 1:
The patent uses a self-complementary AAV6 vector as an intermediary delivery system that enables precise control of transgene expression. The vector design includes specific regulatory elements that ensure physiologically appropriate expression levels of RAG2, avoiding the dysregulation seen with viral vectors.
Solution Approach 2:
The patent modifies the expression parameters by using a self-complementary AAV6 vector with optimized promoter elements and regulatory sequences. This changes the expression dynamics to achieve stable, physiologically appropriate RAG2 levels rather than the inadequate or dysregulated expression from previous viral vector approaches.
3Manufacturing precision
If CRISPR/Cas9-mediated gene editing is used to correct RAG2 deficiency, then targeted gene insertion can be achieved, but double-stranded plasmid DNA toxicity occurs in primary cells
Solution Approach 1:
The patent uses transient transfection of linear DNA fragments or ssODNs for HDR template delivery rather than stable plasmid maintenance. These short-lived DNA templates perform their function during the brief window of HDR activity and are then degraded, avoiding the chronic toxicity of maintaining double-stranded plasmid DNA in primary hematopoietic cells.
4Manufacturing precision
If homology-directed repair is used for targeted insertion, then precise gene correction can be achieved, but HDR is restricted to S and G2 phases posing challenges for quiescent stem cells
Solution Approach 1:
The patent performs gene editing ex vivo on harvested hematopoietic stem cells before reinfusion. This preliminary correction allows the use of cell cycle-synchronized cultures or activated cell states where HDR is active, avoiding the limitation of editing quiescent cells in vivo. The corrected cells are then expanded and reinfused to restore immune function.
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 enables safe and effective correction of RAG2 deficiencies, promoting the development of functional T and B cells, reducing the risk of complications associated with traditional treatments and achieving sufficient RAG2 expression for immune cell development.
Implementation Method 1
a DNA double-strand break (DSB) induced by the nuclease acts as a target for homology-directed repair (HDR)
Implementation Method 2
a DNA double-strand break (DSB) induced by the nuclease acts as a target for homology-directed repair (HDR) using a donor DNA template containing homologous sequences to those flanking the cut site
Data Source
AI summary
The present disclosure provides methods and compositions for treating RAG2 deficiencies in subjects, comprising genetically modifying cells from the subjects ex vivo by integrating a functional, codon-optimized RAG 2 cDNA at the endogenous RAG2 locus.