Abl is a conserved non-receptor tyrosine kinase involved in many cell biological processes, including cytoskeletal rearrangement, cell adhesion, cell migration and apoptosis. To understand the in vivo role of Abl, I am studying the Abl homolog, ABL-1. ABL-1 inhibits three processes in which cytoskeletal regulation is involved: engulfment of apoptotic cells, cell migration and apoptosis. The engulfment of the apoptotic cells is mediated by three parallel and partially redundant core signalling pathways (comprised of CED-1, CED-6, CED-7, DYN-1 and CED-2, CED-5, CED-10, CED-12 and ABI-1). CED-1, 6 and 7 activate the GTPase DYN-1 Dynamin, a regulator of membrane dynamics. CED-2, 5 and 12 activate the small GTPase CED-10 Rac, a regulator of the actin cytoskeleton. ABI-1, the target of ABL-1 in these processes, is also a regulator of the actin cytoskeleton. I aimed to identify the proteins through which ABI-1 acts in engulfment and migration to find potential downstream targets within Abl-dependent pathways. Abi proteins are found in several protein complexes in mammals. One such complex is the Scar/WAVE complex, called the GEX complex in worms, which mediates actin polymerization in response to activation by Rac signaling. Because all GEX genes are essential to the viability of the animal, I am using partial knockdown of gex complex genes using feeding RNAi to test their roles in engulfment. I have analyzed gex complex gene engulfment phenotypes using feeding RNAi in worms with mutations in
dyn-1 and
ced-10 pathway genes to look for enhancement of the engulfment defects. To date I have shown that partial knockdown of
wve-1 and
gex-2 enhance the engulfment defects of both
ced-1/6/7 and
ced-2/5/10/12 pathways. In addition,
gex-2 enhances the distal tip cell migration defect of a
ced-2 null mutation. To test if
wve-1 and
gex-2 affect the engulfment process independent of
abl-1, I assayed the effect of
wve-1 and
gex-2 RNAi in strains doubly mutant for
ced-10 pathway genes and
abl-1. In these strains the loss of
wve-1 and
gex-2 enhances the engulfment defects to the same degree regardless of the presence of functional ABL-1, indicating that
wve-1 and
gex-2 act downstream of or in parallel to
abl-1. These preliminary results indicate that WVE-1, GEX-2, like ABI-1, promote the engulfment of apoptotic cells and cell migration downstream of or in parallel to ABL-1. My studies are now focused on dissecting how these proteins act in relation to the other known proteins involved in these processes by the analysis of double mutant animals and studies of physical interactions among the SCAR/WAVE proteins, ABL-1 and other proteins involved in these processes.