Cas9 RuvC Domain Mutations for Specificity
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Solution Overview
Problem
Current CRISPR-Cas9 genome editing tools face challenges with off-target DNA cleavage and reduced on-target efficiency due to mismatches, limiting their therapeutic potential.
Innovation Solution
Development of a Cas9 variant with mutations in the RuvC domain, maintaining at least 80% sequence identity to the parent Cas9, which enhances specificity and retains high cleavage rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-fidelity Cas9 variants with improved mismatch discrimination are developed, then specificity is improved, but on-target DNA cleavage rates are severely reduced
Solution Approach 1:
The patent applies parameter changes by introducing specific amino acid mutations (e.g., R661A, Q695A, H698A) in the RuvC domain of Cas9 to alter its mismatch discrimination parameters. These mutations modify the enzyme's specificity without compromising its catalytic activity, thereby achieving both high specificity and maintained on-target cleavage rates simultaneously.
Solution Approach 2:
The patent applies local quality by making targeted mutations specifically in the RuvC domain, which is responsible for mismatch recognition. By localizing the changes to this specific domain rather than altering the entire protein, the invention improves specificity at the critical site while preserving the overall functionality and cleavage rate of the Cas9 enzyme.
2Object-affected harmful factors
If Cas9 variants with greater discrimination against mismatches are designed, then off-target DNA cleavage is reduced, but on-target DNA cleavage rates are reduced
Solution Approach 1:
The patent introduces specific mutations (R661A, Q695A, H698A) that change the kinetic parameters of Cas9 mismatch discrimination. These parameter changes enable the enzyme to distinguish more effectively between perfect matches and mismatches, reducing off-target cleavage while maintaining efficient on-target activity through optimized catalytic rates.
Solution Approach 2:
The patent converts the previously harmful effect of mismatch tolerance into a beneficial feature by designing Cas9 variants that selectively tolerate certain mismatches in the PAM region while maintaining high discrimination against mismatches in the seed region. This selective tolerance approach reduces off-target effects while preserving on-target efficiency.
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
The Cas9 variant achieves improved specificity by reducing off-target DNA cleavage while maintaining efficient on-target DNA cleavage, thereby enhancing the precision and effectiveness of genome editing.
Implementation Method 1
the isolated Cas9 variant or fragment has endonuclease activity
Data Source
AI summary
Disclosed herein are methods and compositions relating to a mutated version of Cas9. This mutation or mutations can be in the RuvC domain of Cas9. The mutated Cas9 can have decreased cleavage of mismatched target compared to a wild type Cas9.