SpCas9 Mutations Balancing Specificity and On-Target Potency
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Solution Overview
Problem
Existing SpCas9 variants face challenges with reduced on-target potency and specificity, limiting their effectiveness in gene editing applications, particularly in human cells.
Innovation Solution
Development of novel point mutations in the SpCas9 protein, such as D54A, to enhance on-target editing activity while maintaining specificity, using a CRISPR/Cas endonuclease system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If point mutations are introduced to improve SpCas9 specificity, then off-target editing is reduced, but on-target potency is significantly decreased
Solution Approach 1:
The patent introduces point mutations at specific positions (e.g., D54A, N46L, S55N) to change the biochemical parameters of SpCas9, thereby improving specificity while maintaining or enhancing on-target activity. These parameter changes in the protein structure resolve the contradiction by allowing simultaneous optimization of both specificity and potency.
2Productivity
If SpCas9 on-target activity is increased through mutagenesis, then gene editing efficiency is improved, but off-target effects may increase
Solution Approach 1:
The patent applies parameter changes through specific point mutations that enhance on-target cleavage activity while maintaining specificity. Mutations such as D54A and combinations with other residues modify the enzyme's kinetic parameters to favor on-target binding and cleavage, thereby increasing productivity without proportionally increasing harmful off-target effects.
3Adaptability or versatility
If SpCas9 variants with alternative PAM preference are developed, then targetable site diversity is increased, but on-target potency is reduced
Solution Approach 1:
The patent modifies PAM recognition parameters through point mutations in the PAM-interacting region of SpCas9. These parameter changes allow the enzyme to recognize alternative PAM sequences while maintaining or improving on-target cleavage potency, thereby resolving the contradiction between versatility and productivity.
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 novel SpCas9 mutations significantly improve on-target editing efficiency in human cells without increasing off-target effects, making them suitable for advanced gene editing platforms like base editing and prime editing.
Implementation Method 1
SpCas9 is an RNA-guided endonuclease utilizing the Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR) adaptive immune system from Streptococcus pyogenes
Data Source
AI summary
This invention pertains to mutant Cas9 nucleic acids and proteins for use in CRISPR/Cas endonuclease systems, and their methods of use. In particular, the invention pertains to an isolated mutant Cas9 protein, wherein the isolated mutant Cas9 protein is active in a CRISPR/Cas endonuclease system, wherein the CRISPR/Cas endonuclease system displays increased on-target editing activity relative to a wild-type CRISPR/Cas endonuclease system. The invention also includes isolated nucleic acids encoding mutant Cas9 proteins, ribonucleoprotein complexes and CRSPR/Cas endonuclease systems having mutant Cas9 proteins that display increased on-target editing activity relative to a wild-type CRISPR/Cas endonuclease system.