Cytokinesis without myosin II

The ability of substrate-anchored Dictyostelium cells to divide without myo sin II has opened the possibility of analysing the formation of cleavage fu rrows in the absence of a contractile ring made of filamentous myosin and a ctin. Similar possibilities exist in mutants of budding yeast and, less str ictly, also in drug-treated mammalian cells. Myosin-II-independent activiti es in Dictyostelium include the microtubule-induced programming of the cell surface into ruffling areas and regions that are converted into a concave furrow, as well as the translocation of cortexillins and cross-linked membr ane proteins towards the cleavage furrow. A centripetal flow of actin filam ents followed by their disassembly in the cleavage furrow is proposed to un derlie the translocation.