Rapid and robust validation of pooled CRISPR knockout screens using CelFi

Pooled CRISPR screens are vital in the unbiased interrogation of gene function and are instrumental in uncovering therapeutic targets and biological processes. However, follow-up hit validation is critical to confirm observed results. Researchers need a simple and robust approach to rapidly verify putative hits and test resulting observations. Thus, we developed a CRISPR-based method for hit validation that tests the effect of a genetic perturbation on cell fitness. By editing target loci and monitoring the indel profiles over time, we have created a Cellular Fitness (CelFi) assay that can elucidate cellular vulnerabilities and verify hits from pooled CRISPR knockout screens. Unlike traditional cellular fitness assays that evaluate viability over time, the CelFi assay correlates changes in the indel profile at the target gene with a selective growth advantage or disadvantage in individual cells over time. Moreover, the CelFi assay can be utilized to evaluate gene dependencies and test new hypotheses, regardless of variations in single guide RNA optimization, ribonucleoprotein concentration, and gene copy number.