CRISPR/Cas9 Safe Harbor Integration for iPSC Production
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for producing induced pluripotent stem cells (iPSCs) using CRISPR/Cas systems face challenges such as inefficiency, random integration of reprogramming factors, and off-target mutagenesis, particularly due to limitations in existing safe harbor sites like AAVS1, CCR5, and hROSA26, which can affect gene expression and increase the risk of infections.
Innovation Solution
A method involving a CRISPR/Cas9 system with a double-nicking mechanism using paired guide RNAs (gRNAs) to precisely integrate reprogramming factors into the CRISPR/Cas9-accessible safe harbor-1 (CASH-1) site on chromosome 1, minimizing off-target effects and ensuring consistent expression by using a vector containing nucleic acids encoding gRNA 1 and gRNA 2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional genome editing tools (ZFNs, TALENs) are used to integrate reprogramming factors, then integration can be achieved, but the process requires repeated work and creates double-strand breaks by artificial nuclease domains
Solution Approach 1:
The patent replaces traditional mechanical genome editing tools (ZFNs, TALENs) with the CRISPR/Cas9 system, which uses RNA-guided nucleases instead of protein-DNA recognition. This substitution simplifies the editing process by replacing complex protein engineering requirements with easier RNA sequence design, while achieving the same genome integration function.
2Productivity
If single gRNA CRISPR/Cas9 system is used, then genome editing is efficient, but off-target mutagenesis increases due to tolerance of mismatches
Solution Approach 1:
The patent divides the single gRNA system into two separate gRNAs that work together in a dual-nicking configuration. Each gRNA targets a different strand and creates a nick rather than a full cut, requiring both gRNAs to bind correctly at the target site. This segmentation increases specificity by recognizing more base pairs while maintaining editing efficiency through coordinated action of both guides.
Solution Approach 2:
The patent introduces a dual-nicking mechanism as an intermediary step between gRNA binding and DNA cleavage. Instead of direct cleavage by a single gRNA-Cas9 complex, the system uses two separate nicking events that must both occur correctly, providing an additional layer of specificity verification before permanent DNA modification occurs.
3Reliability
If existing safe harbor sites (AAVS1, CCR5, hROSA26) are used for integration, then reprogramming factor expression can be achieved, but random integration and insertional mutations occur
Solution Approach 1:
The patent replaces traditional non-specific integration methods with CRISPR/Cas9-mediated targeted integration. The RNA-guided nuclease system provides precise positioning at the CASH-1 site, replacing random or semi-random integration mechanisms with programmable, sequence-specific DNA cleavage and repair that directs reprogramming factor insertion to a predetermined safe location.
4Reliability
If CCR5 locus is used for safe harbor integration, then integration can occur, but expression of integrated transgenes is lower compared to AAVS1 locus
Solution Approach 1:
The patent changes the genomic location parameter from traditional safe harbor sites (AAVS1, CCR5, hROSA26) to a newly identified CASH-1 site. This parameter change optimizes both integration stability and transgene expression levels simultaneously, as CASH-1 exhibits superior characteristics for sustained, high-level expression compared to the alternative loci.
5Quantity of substance
If AAVS1 locus is used for safe harbor integration, then transgene expression can be achieved, but adjacent gene expression (PPP1R12C) is reduced by 50% to 100%
Solution Approach 1:
The patent extracts the integration event from the problematic AAVS1 locus and relocates it to the CASH-1 site. By removing the integration event from the AAVS1 genomic context, the harmful effect on adjacent PPP1R12C gene expression is eliminated, while maintaining the desired transgene expression at the new location.
6Quantity of substance
If hROSA26 locus is used for safe harbor integration, then transgene expression can occur, but the locus is located in a gene-rich region with lacking safety data
Solution Approach 1:
The patent replaces integration at the hROSA26 locus with integration at the CASH-1 site. This substitution moves the integration event from a gene-rich region with insufficient safety characterization to a safer genomic location, reducing potential risks while preserving transgene expression capability.
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 efficient and safe production of iPSCs with reduced off-target mutagenesis, ensuring consistent expression of reprogramming factors and satisfying the criteria for a safe genomic harbor, thus overcoming the limitations of previous methods.
Implementation Method 1
this system requires a 20-nucleotide-long CRISPR RNA that must be complementary to a target sequence upstream of a 5′ protospacer adjacent motif (PAM) site
Implementation Method 2
The resulting DSB is repaired by non-homologous end joining (NHEJ) or homology-directed repair (HDR)
Implementation Method 3
a double-nicking CRISPR/Cas9 system using paired gRNAs is suitable for genome editing with increased specificity and minimized off-target mutagenesis by expanding the number of bases specifically recognized at the target site
Data Source
AI summary
A method for producing induced pluripotent stem cells by using CRISPR/Cas system is disclosed. The method includes a step of inserting a reprogramming factor by using a CRSPR/Cas system containing in a safe harbor of somatic cells a delivery means including two guides RNAs and a Cas protein-encoding nucleic acid. The method can prevent mutation in an off-target region and integrate a reprogramming factor into an on-target region safely and specifically, and regulates the reprogramming factor with doxycycline to guarantee consistent expression, whereby induced pluripotent stem cells can be effectively produced. In addition, the induced pluripotent stem cells produced by the method exhibit multipotent markers similar to those of human embryonic stem cells and can differentiate into derivatives of all the three germ layers.