In the Drosophila embryo, nuclear divisions 10-13 occur in a syncytium with transient membrane furrows separating neighboring nuclei before the occurrence of cellularization. This process is driven by cytoskeletal and membrane trafficking networks, and while RalA and Rab8 have been identified to drive membrane addition to furrows, less is known about the control of dynamic F-actin networks needed for furrow formation. Here, the role of the DOCK protein Sponge (Spg) in furrow formation is explored through shRNA knockdown and live-imaging of syncytial Drosophila embryos. I have found that Spg is required for furrow ingression and that without Spg, furrows can only reach 25% of their wild-type length. This is due to a lack of branched F-actin on apical caps and furrows, and Spg is found to be a key regulator in bringing components of the Arp pathway to these structures. Finally, I have demonstrated the requirement for this branched F-actin network in potentiating ingression and linear F-actin networks that are localized along the length of syncytial furrows
