Figure 3. Regulatory mechanisms keeping furrow growth in check. (A) Reduction of centripetal plasma membrane growth by Amphiphysin-dependent endocytic tubules that seem to act as basal reservoirs to buffer apicolateral membrane addition. (B) Inhibition of the Rho1-Diaphanous/non-muscle myosin II pathway by the Arf-GEF Steppke to prevent premature perpendicular expansion of basal furrow tips during peripheral nuclear division cycles and early cellularization. (C) Restraint of actomyosin rings by a PIP3-Bottleneck pathway to prevent premature perpendicular expansion of basal furrow tips during mid-late cellularization.