Early zygotic gene product Dunk interacts with anillin to regulate Myosin II during Drosophila cleavage

Drosophila cellularization is a special form of cleavage that converts syncytial embryos into cellular blastoderms by partitioning the peripherally localized nuclei into individual cells. An early event in cellularization is the recruitment of non-muscle myosin II ("myosin") to the basal tip of cleavage furrows, where myosin forms an interconnected basal array before reorganizing into individual cytokinetic rings. The initial recruitment and organization of basal myosin are regulated by a cellularization-specific gene, dunk, but the underlying mechanism is unclear. Through a genome-wide yeast two-hybrid screen, we identified anillin (Scraps in Drosophila), a conserved scaffolding protein in cytokinesis, as the primary binding partner of Dunk. We show that Dunk regulates the localization of anillin at the cleavage furrows during early cellularization and functionally interacts with anillin in regulating basal myosin. Furthermore, we show that anillin colocalizes with myosin since the onset of cellularization and is required for the initial recruitment and maintenance of myosin at the basal array, prior to the well-documented function of anillin in regulating cytokinetic ring assembly. Based on these results, we propose that Dunk regulates myosin recruitment and organization during early cellularization by interacting with and regulating anillin.