ARROW: Allele-Specific Recombined gRNA Design for Reduced Off-Target with Enhanced Specificity

Area of Science:

• Molecular Biology
• Gene Editing Technologies

Background:

• CRISPR-Cas9 genome editing offers precise therapeutic potential for dominant inherited diseases.
• Cas9-guide RNA (gRNA) complexes often lack specificity, tolerating mismatches and complicating allele discrimination.
• Previous attempts to improve specificity by altering gRNAs lacked systematic evaluation of mismatch effects.

Purpose of the Study:

• To develop and evaluate a strategy for enhancing CRISPR-Cas9 specificity by introducing deliberate mismatches into gRNAs.
• To systematically assess the impact of different mismatch types and positions on allele-specific editing outcomes.
• To minimize off-target effects and improve the safety of genome editing interventions.

Main Methods:

• Developed a strategy involving the intentional introduction of mismatches into guide RNAs (gRNAs).
• Comprehensively evaluated the editing performance of modified gRNAs.
• Tested the approach on cancer-associated heterozygous point mutations (EGFR L858R and KRAS G12V).

Main Results:

• Established an efficient strategy for selective mutant allele editing by reducing Cas9 sequence tolerance.
• Demonstrated successful allele-specific editing of EGFR L858R and KRAS G12V mutations.
• Minimized editing of corresponding wild-type alleles, indicating enhanced specificity.

Conclusions:

• Strategic incorporation of mismatches into gRNAs significantly enhanced editing specificity for single-base mutant alleles compared to perfectly matched gRNAs.
• The findings represent a substantial improvement in the precision and safety of CRISPR-based genome editing for cancer therapy.
• This approach is particularly beneficial for targeting mutant alleles in therapeutic applications.