Required for cytokinesis. Essential for the structural integrity of the cleavage furrow and for completion of cleavage furrow ingression and proper formation of the midbody. Required during cellularization of syncytial embryos for the proper formation and function of the furrow canals, the stable inward folds of the plasma membrane which separate the peripheral nuclei. Also required for the formation of the pole cells, the progenitors of the adult germline which are formed by cytokinesis of the cytoplasmic buds at the posterior pole of the syncytial embryo. Essential for embryonic viability. Interacts with and bundles F-actin. Mainly found in the nucleus during interphase. Colocalizes with cortical F-actin upon nuclear envelope breakdown in mitosis and subsequently concentrates in the area of the prospective contractile ring in anaphase. This pattern persists until telophase, when the protein becomes concentrated in the midbody. Accumulates in the nucleus of newly divided cells in a diffuse staining pattern, thereby restarting the cycle. Accumulates in the ring canals that interconnect cells of the germline cysts in males and the ovarian follicles in females. These structures develop from arrested contractile rings after a specialized cytokinesis in which the closing of the invaginating plasma membrane is incomplete. Also concentrates in the arrested cleavage furrows that initially link the oocyte to its 15 nurse cells in the early egg chamber and is subsequently lost from these furrows as germline cell division is completed. Expressed throughout development and at reduced levels late in embryogenesis. Localizes to the embryonic cortex and to the metaphase furrows which separate mitotic nuclei in the syncytial embryo prior to cellularization. Concentrates in the leading edges of the furrow canals at the onset of cellularization.