Inducible CRISPR-Cas9 screening platform to interrogate non-proliferative cellular states.

Abstract

CRISPR screens have revolutionized the study of diverse biological processes, particularly in cancer research. Both pooled and arrayed CRISPR screens have facilitated the identification of essential genes for cell survival and proliferation, drivers of drug resistance and synthetic lethal interactions. However, applying loss-of-function CRISPR screening to non-proliferative states remains challenging, largely because of slower editing and the poor sensitivity of identifying guide RNAs that 'drop out' in a population of non-dividing cells. Here, we present a detailed protocol to accomplish this, using an inducible Cas9 system that offers precise temporal control over Cas9 expression. This inducible system allows gene editing to occur only after the non-proliferative state is fully established. We describe the complete procedure for generating an inducible Cas9-expressing model and for measuring editing efficiency by using flow cytometry. In addition, we discuss how to optimize key parameters for performing successful CRISPR screens in various non-proliferative states. We describe a detailed workflow for performing a screen in senescent cells to identify senolytic targets. This protocol is accessible to researchers with experience in molecular biology techniques and can be completed in 8-12 weeks, from the generation of an inducible Cas9 cell line clone to the analysis of a CRISPR screen for hit identification. These techniques can be applied by researchers across different fields, including stem cell differentiation, immune cell development, aging and cancer research.