Variant Guide RNA Scaffolds Enhance SpCas9 Specificity
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Solution Overview
Problem
Current CRISPR-Cas9 systems for genome editing exhibit varying efficiencies and specificity issues, particularly in therapeutic applications, with existing engineered guide RNA scaffolds compromising on-target editing while potentially increasing off-target edits, and no variant has shown enhanced activity for SpCas9.
Innovation Solution
Development of variant guide RNA scaffolds with specific mutations in the stem-loop 2 region that strengthen interactions with the Cas9 enzyme, enhancing on-target editing and specificity, including ribonucleoprotein complexes with these variants, to improve genome-wide targeting accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If existing engineered guide RNA scaffolds are used to increase on-target editing, then editing efficiency is improved, but off-target activity increases and genome-wide accuracy is compromised
Solution Approach 1:
The patent applies parameter changes by systematically varying the scaffold sequence parameters (nucleotide compositions, stem-loop structures, and sequence lengths) to identify optimal configurations. Through high-throughput screening of multiple scaffold variants with different parameters, the invention discovered sequences that achieve enhanced on-target editing while maintaining low off-target activity, thus resolving the contradiction between editing efficiency and genome-wide accuracy
Solution Approach 2:
The patent applies local quality by making specific localized modifications to particular regions of the guide RNA scaffold (such as the stem-loop 2 region and tetraloop structures) rather than uniform changes throughout. These targeted local optimizations allow the scaffold to enhance Cas9 binding and on-target activity at specific locations while preserving overall specificity and reducing off-target effects
2Adaptability or versatility
If Cas9 protein engineering is performed to improve specificity and targeting scope, then targeting capability is enhanced, but system complexity increases
Solution Approach 1:
The patent applies universality by developing guide RNA scaffold variants that can universally enhance the performance of SpCas9 across diverse target sites. The optimized scaffolds serve multiple functions: improving on-target editing efficiency, maintaining genome-wide specificity, and working effectively with various protospacer sequences. This universal enhancement approach avoids the need for site-specific Cas9 engineering, thereby expanding targeting scope while minimizing system complexity
3Stability of the object's composition
If scaffold sequence is engineered to strengthen interaction with Cas9, then assembly and stability are improved, but off-target edits may increase
Solution Approach 1:
The patent applies parameter changes by systematically optimizing the scaffold sequence parameters including GC content, stem-loop structure parameters, and nucleotide composition at specific positions. Through high-throughput screening, the invention identified parameter combinations that achieve optimal binding stability with Cas9 while maintaining appropriate dissociation dynamics to prevent off-target binding, thus resolving the contradiction between assembly stability and off-target edit reduction
Data Source
AI summary
Engineered guide RNAs having enhanced stability of interaction with Cas enzymes are disclosed. The variant sgRNAs include engineered nucleic acids in or around the stem-loop 2 region which enhance interaction with the Cas9 enzyme and impart enhanced specificity and on-target editing activity. Compositions and methods of engineered guide RNAs are provided for enhanced genomic engineering with increased on-off target specificity and on-target editing efficacy.