Complementary information derived from CRISPR Cas9 mediated gene deletion and suppression.

Area of Science:

• Molecular Biology
• Genomics
• Genetic Engineering

Background:

• CRISPR-Cas9 enables genome editing and loss-of-function screens.
• Cas9 endonuclease expression can cause gene-independent responses, limiting its use in screens.
• Catalytically inactive Cas9 (dCas9) fused with KRAB offers an alternative for gene suppression via transcriptional interference.

Purpose of the Study:

• Directly compare CRISPR-Cas9 (CRISPRc) and KRAB-dCas9 (CRISPRi) for identifying cell essential genes in loss-of-function screens.
• Evaluate the efficiency and potential biases of each CRISPR-based screening approach.
• Determine if combining CRISPRc and CRISPRi offers complementary insights into genetic screens.

Main Methods:

• Genome editing with CRISPR-Cas9 (CRISPRc) was performed.
• Gene suppression using KRAB-fused catalytically inactive Cas9 (CRISPRi) was implemented.
• Library construction for CRISPRi was optimized by analyzing transcriptional start sites (TSS).

Main Results:

• CRISPRc identified 98% of previously defined cell essential genes.
• CRISPRi, after optimization, identified 92% of core cell essential genes.
• CRISPRi showed no bias towards copy number alteration regions, unlike CRISPRc, but produced false positives with bidirectional promoters.

Conclusions:

• CRISPRc and CRISPRi exhibit distinct off-target effects.
• Combining CRISPRc and CRISPRi approaches provides complementary data for loss-of-function genetic screens.
• Both CRISPR-based methods are valuable tools for essential gene identification, with different strengths and weaknesses.