Cell migration CRISPRi screens in human neutrophils reveal regulators of context-dependent migration and differentiation state

Neutrophils are the most abundant leukocyte in humans and provide a critical early line of defense as part of our innate immune system. Their exquisite sensitivity to chemical gradients and ability to rapidly migrate make them especially suited to protect against infection. However, their terminal differentiation status and short lifetime (on the order of days) have hindered their study. Furthermore, while modern CRISPR-based gene perturbation strategies now allow comprehensive, genome-scale screens in human cells, their application to complex and dynamic processes like cell migration remain limited. Using HL-60 cells, a leukemia cell line that can be differentiated into neutrophil-like cells, we have developed multiple cell migration screen strategies that provide comprehensive, genome-wide discovery of molecular factors that are critical for directed (chemotaxis), undirected (chemokinesis), and 3D amoeboid cell migration in these fast-moving cells. Combining these assays with additional, pooled, genome-wide CRISPR interference dropout screens of cell proliferation and neutrophil differentiation, we have identified a comprehensive set of genes that are important across the processes of cellular growth, differentiation, and migration. This combined dataset highlights a particular reliance upon mTORC1 signaling that alters neutrophil lifetime, migration phenotype, and sensitivity to chemotactic cues. Across our cell migration screens, we identified several hundred genes important for migration including those with specific roles only in particular migratory contexts. This genome-wide screening strategy, therefore, provides an invaluable approach to the study of neutrophils and provides a resource that will inform future studies of cell migration in these and other rapidly migrating cells.