TI - Abl Kinase Inhibits the Engulfment of Apopotic Cells in Caenorhabditis elegans C.elegans Abl Inhibits Cell Engulfment . . AB - The engulfment of apoptotic cells is required for normal metazoan development and tissue remodeling . In Caenorhabditis elegans , two parallel and partially redundant conserved pathways act in cell -corpse engulfment . One pathway includes the adaptor protein CED-2 CrkII and the small GTPase CED-10 Rac , and acts to rearrange the cytoskeleton of the engulfing cell . The other pathway includes the receptor tyrosine kinase CED-1 and might recruit membranes to extend the surface of the engulfing cell . Although many components required for engulfment have been identified , little is known about inhibition of engulfment . The tyrosine kinase Abl regulates the actin cytoskeleton in mammals and Drosophila in multiple ways . For example , Abl inhibits cell migration via PHOSphorylation of CrkII . We tested whether ABL-1 , the C.elegans ortholog of Abl , inhibits the CED-2 CrkII -dependent engulfment of apoptotic cells . Our genetic studies indicate that ABL-1 inhibits apoptotic cell engulfment , but not through CED-2 CrkII , and instead acts in parallel to the two known engulfment pathways . The CED-10 Rac pathway is also required for proper migration of the distal tip cells ( DTCs ) during the development of the C.elegans gonad . The loss of ABL-1 function partially restores normal DTC migration in the CED-10 Rac pathway mutants . We found that ABI-1 the C.elegans homolog of mammalian Abi ( Abl interactor ) proteins , is required for engulfment of apoptotic cells and proper DTC migration . Like Abl , Abi proteins are cytoskeletal regulators . ABI-1 acts in parallel to the two known engulfment pathways , likely downstream of ABL-1 . ABL-1 and ABI-1 interact physically in vitro . We propose that ABL-1 opposes the engulfment of apoptotic cells by inhibiting ABI-1 via a pathway that is distinct from the two known engulfment pathways .