RAB-35 and ARF-6 GTPases Mediate Engulfment and Clearance Following Linker Cell-Type Death

Clearance of dying cells is essential for development and homeostasis. Conserved genes mediate apoptotic cell removal, but whether these genes also control non-apoptotic cell removal is a major open question. L inker c ell-type d eath (LCD) is a prevalent non-apoptotic developmental cell death process with features conserved from C. elegans to vertebrates. Using microfluidics-based long-term in vivo imaging, we show that unlike apoptotic cells, the C. elegans linker cell, which dies by LCD, is competitively phagocytosed by two neighboring cells, resulting in cell splitting. Subsequent cell elimination does not require apoptotic engulfment genes. Rather, we find that RAB-35 GTPase is a key coordinator of competitive phagocytosis onset and linker cell degradation. RAB-35 binds CNT-1, an ARF-6 GTPase activating protein; removes ARF-6, a degradation inhibitor, from phagosome membranes; and recruits RAB-5 and RAB-7 GTPases for phagolysosome maturation. We propose that RAB-35 and ARF-6 drive an evolutionarily conserved program eliminating cells dying by LCD.