CRISPR/Cas9 Screening to Identify Conditionally Essential Genes in Human Cell Lines

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Forward genetic screens define gene dependencies in proliferating human cells.
• In vitro screens often overlook the impact of medium composition on gene essentiality.
• Understanding nutrient-mediated gene essentiality is crucial for cancer research.

Purpose of the Study:

• To develop and describe a protocol for CRISPR/Cas9 loss-of-function screens to assess gene essentiality across different cell culture media.
• To identify genes whose essentiality is dependent on specific medium compositions in human cell lines.

Main Methods:

• Utilizing CRISPR/Cas9-based loss-of-function screens with a single-guide RNA (sgRNA) library.
• Infecting target human cell lines with lentivirus carrying the sgRNA library and determining optimal infection titers.
• Screening transduced cells in at least two distinct cell culture media and collecting genomic DNA (gDNA) at multiple time points.
• Employing high-throughput sequencing to quantify sgRNA barcode abundances and an analytical pipeline to identify medium-essential genes.

Main Results:

• The protocol successfully enables the assessment of gene essentiality variation based on medium composition.
• Identification of candidate genes whose function is critical only in specific media formulations.
• Provides a framework for discovering nutrient-specific genetic dependencies in human cell lines.

Conclusions:

• Medium composition significantly influences gene essentiality in human cell lines.
• This CRISPR/Cas9 screening approach is effective for uncovering medium-dependent genetic vulnerabilities.
• The findings have implications for personalized cancer therapy and cell culture optimization.