Optimizing CRISPR/Cas9 Editing of Repetitive Single Nucleotide Variants

Area of Science:

• Molecular Biology
• Genetics
• Biotechnology

Background:

• CRISPR/Cas9, base editors, and prime editors are key genome editing tools.
• Optimizing CRISPR/Cas9 for homology directed repair (HDR)-mediated single nucleotide substitutions remains a significant challenge.
• Existing studies often lack validation in clonal cell lines or for difficult genetic loci.

Purpose of the Study:

• To investigate factors influencing CRISPR/Cas9 editing efficiency.
• To compare the effectiveness of different optimization strategies.
• To provide a validated protocol for improving genome editing outcomes.

Main Methods:

• Conducted 95 transfections across two cell lines (colony forming and immortalized).
• Evaluated effects of donor template modifications, component concentrations, HDR enhancers, and cold shock.
• Utilized next-generation sequencing (NGS) and digital droplet PCR (ddPCR) for efficiency assessment.

Main Results:

• In silico guide RNA efficiency predictions showed poor correlation with in vitro activity.
• Observed editing efficiencies of 5-12% in transfected populations, decreasing to 1% upon clonal isolation.
• Demonstrated significant variability in CRISPR efficiency based on cell model and target locus.

Conclusions:

• Successful genome editing necessitates empirical comparison of systems and modifications for optimal protocols.
• Validated HDR-boosting modifications for CRISPR/Cas9 are presented.
• A flowchart is provided to guide researchers through the genome editing process.