| Popis: |
A striking feature of lattice cells (LCs) in the developing Drosophila retina is their constant movement and changes in size and shape before attaining their final form. Previously we showed that repeated contraction and expansion of apical cell contacts contribute to these movements and shape changes. Here we describe a second factor required for these dynamics, the assembly of a medioapical actomyosin ring composed of nodes linked by filaments that attract each other, fuse, and contract the apical cell area of LCs. This medioapical actomyosin network is dependent on Rho1 and its known effectors. Contraction of the apical cell area alternates with relaxation generating pulsatile changes in apical cell area. Strikingly, cycles of contraction and relaxation of cell area within one LC are reciprocally synchronized between adjacent LCs. Further, we identified upstream Rho1 regulators in a genetic screen and found that RhoGEF2 activated these Rho1 functions while RhoGAP71E/C-GAP inhibited them. Thus, Rho1 signaling regulates pulsatile contraction of medioapical actomyosin networks exerting force on neighboring cells, coordinating cell behavior across the epithelium. This ultimately serves to control cell shape and maintain tissue integrity through the process of epithelial morphogenesis of the retina. |
