A genome-wide CRISPR/Cas9 screen to identify phagocytosis modulators in monocytic THP-1 cells

Phagocytosis of microbial pathogens, dying or dead cells, and cell debris is essential to maintain tissue homeostasis. Impairment of these processes is associated with autoimmunity, developmental defects and toxic protein accumulation. However, the underlying molecular mechanisms of phagocytosis remain incompletely understood. Here, we performed a genome-wide CRISPR knockout screen to systematically identify regulators involved in phagocytosis of Staphylococcus (S.) aureus by human monocytic THP-1 cells. The screen identified 75 hits including known regulators of phagocytosis, e.g. members of the actin cytoskeleton regulation Arp2/3 and WAVE complexes, as well as genes previously not associated with phagocytosis. These novel genes are involved in translational control (EIF5A and DHPS) and the UDP glycosylation pathway (SLC35A2, SLC35A3, UGCG and UXS1) and were further validated by single gene knockout experiments. Whereas the knockout of EIF5A and DHPS impaired phagocytosis, knocking out SLC35A2, SLC35A3, UGCG and UXS1 resulted in increased phagocytosis. In addition to S. aureus phagocytosis, the above described genes also modulate phagocytosis of Escherichia coli and yeast-derived zymosan A. In summary, we identified both known and unknown genetic regulators of phagocytosis, the latter providing a valuable resource for future studies dissecting the underlying molecular and cellular mechanisms and their role in human disease.