Figure 3.

Rho GTPases in bleb-driven migration. The predominant Rho GTPase involved in bleb-driven migration is RhoA, acting through ROCK to stimulate myosin light chain phosphorylation (pMLC) and hence cortical actomyosin contractility, which is higher at the front and back of the cell than on the sides. At the back of the cell, ezrin is associated with the actin cortex and reduces bleb formation [111]. At the front of the cell, actomyosin contractility leads to focal detachment of the plasma membrane from the actin cortex to form blebs, which initially do not contain actin filaments (shown in blue). Subsequently actin polymerizes on the bleb membrane to stabilize the protrusion, eventually leading to bleb retraction. This could be mediated by Rac, which as activated at the front of blebbing primordial germ cells in zebrafish by the G-protein subunits Gβγ.