Blebs do the locomotion

During amoeboid locomotion, which many metazoan cells use to migrate through tissues, actin polymerization is thought to generate filopodia and lamellipodia at the leading edge, which move the cell forward. However, this model does not fully explain amoeboid movement - for example, why do some cells glide and others move jerkily? On p. 3833, Kunito Yoshida and Thierry Soldati propose that the focal production of blebs - transparent, spherical cell-surface protrusions - is also important for amoeboid locomotion. Blebs `blow' out from the cell surface when myosin-II-driven contraction of the back of the cell increases the cytoplasmic fluid pressure. By visualizing the dynamics of F-actin, the authors show that migrating Dictyostelium cells continuously produce these blebs at the leading edge. Pseudopodia extension, cell-body retraction and the speed of cell locomotion are all reduced in myosin-II-null cells, cells treated with the myosin II inhibitor blebbistatin, and cells at high osmolarity - none of which can form blebs. Thus, suggest the authors, efficient amoeboid movement involves formation of blebs and filopodia/lamellipodia, which are produced by two mechanically distinct processes.