CRISPR-Cas Functional Genetic Screening: Traditional Review

The clustered regularly interspaced palindromic repeats (CRISPR)-associated Cas system, derived from the defence mechanism components of prokaryotes, is frequently used as a target specific gene editing tool in in vitro and in vivo studies. Uses of the CRISPR-Cas system include gene deletion, gene insertion, base editing, gene expression editing, genomic locus imaging, epigenetic editing, and diagnostic analysis. Due to the strengths of the system such as flexibility, versatility and easy application, its usage areas have gradually increased. In recent years, CRISPR-Cas9 based functional genetic screen studies have been carried out to understand the roles of genes in the biological processes and cellular functions. CRISPR screens are used to identify genetic factors responsible for disease development and determine their functions, which are necessary for the survival of cells due to disease, especially cancer. CRISPR-Cas9 screens consisting of desing and amplification of the selected gRNA library, cloning in the relevant plasmid, packaging into lentiviruses and lentiviral transduction into cells, phenotypic selection, next generation DNA sequence analysis and bioinformatics analysis, has allowed functional genetic studies that can be performed with high-throughput and high-efficiency. Screening studies can be carried out for different purposes such as investigating pathogen-host interactions, revealing the molecular mechanisms of diseases, identifying novel therapeutic targets and revealing factors that play a key role in treatment resistance. In this review, after a short summary of different CRISPR-Cas systems the basic principles of genetic screening studies, their application and areas of usage will be discussed with selected examples from the current literature. © 2022 by Türkiye Klinikleri.