Fig. 7: The in silico simulation and summarization of follicle cell expansion behavior.

a Representative cartoon to summarize follicle cell basal membrane expansion behavior controlled by Rac1-mediated protrusive force, cortical tension along basal membrane, focal adhesions and their linked local stress fibers. b Representative cartoons for the side view and conformal projection of egg chamber during follicle cell expansion waves. A and P represent anterior and posterior, respectively. c, Simulation of dynamical changes of follicle cell basal domain in one WT tissue during the indicated phases. The shape of follicle cells is illustrated in blue and stress fibers along the D–V direction in the ruffling and spreading phases are illustrated in red. d Combined-factor simulation of oocyte elongation and follicle cell spreading behavior with the indicated genetic backgrounds during the ruffling and spreading phases. Red dotted lines mark the final position of leading follicle cells in WT tissues. In Rho1DN-expressing and Talin RNAi-expressing follicle epithelia, we introduced decreased stress fibers while in Pax-overexpressing follicle epithelium, we introduced increased stress fibers, as observed in experiments. Red color marks stress fibers in follicle cells. e Above: Representative cartoons to summarize the ruffling and spreading phases (here area increasing phase is unshown, considering it as a transition stage between ruffling and spreading phases), two key factors (basal Rac1 and Rho1 activities), as well as different dynamic changes in WT follicle cells and oocyte during follicle cell expansion waves. Bottom: Representative cartoons to summarize cell expansion wave (graded gray rectangles representing the propagation of expansion waves from posterior to anterior region: in most genetic backgrounds, we can detect a gradient of wave occurrence, whereas in dumping defective background, this gradient is disturbed thereby implying the loss of expansion wave), ruffling (cell shape illustrated in green) and spreading of follicle cells (cell migration speed represented by speedometer), and the growth and A–P elongation of the oocyte (blue coverage of follicle cells and egg chamber size), in different genetic backgrounds. Green and red colors mark cell membrane and stress fibers, respectively.