Figure 5.
The spindle pole-cortex geometry regulates the distribution and flow of cortical myosin II.(A and B) Distance between the spindle poles and the cell cortex. (A) The distance from each point on the cell periphery to the nearest spindle pole in embryos depleted of the key microtubule-bundler SPD-1/PRC1 (spd-1(RNAi)) was measured and is presented in the same way as the control embryos shown in Fig. 4 D. (B) Distance from the anterior pole (A-pole) or the posterior pole (P-pole) to the nearest cortex. Rupture of the central spindle by spd-1(RNAi) accelerated the spindle’s pole-to-pole elongation, and thus, the decrease in pole-to-cortex distance. (C and D) Effect of depletion of SPD-1 on the cytoplasmic myosin II particles. (C) Temporal color-coded trajectories of NMY-2::GFP from control (n = 22) or spd-1(RNAi) (n = 23) embryos were overlaid by maximum projection. (D) Cytoplasmic myosin II particles were tracked by automation, and the activity of the cytoplasmic transport toward the centrosomes is presented as cumulative sums after anaphase onset (see Materials and methods and Fig. S3 for more details; mean ± SEM, n = 22 and 23, respectively). (E and F) Density (E) and flow (F) of myosin II in the cell cortex. (E) Cortical myosin II (NMY-2::GFP) was quantified along the cell periphery from the anterior tip to the posterior tip and normalized with the local background and cytoplasmic levels. Average across the embryos from two sets of recordings (22 control and 23 spd-1(RNAi) embryos for 0 to 140 s p.a.o. and 56 control and 19 spd-1(RNAi) embryos for 70 to 210 s p.a.o.) were merged and are presented as a kymograph for each condition (see Materials and methods and Fig. S4 for more details). (F) The flow of myosin II along the cell periphery was computed by one-dimensional particle image velocimetry and is presented as a kymograph. The green signal indicates flow toward the posterior and the magenta toward the anterior. The timing of the transition of the cortical flow into the bidirectional mode (white dashed line) is accelerated in the embryos depleted of SPD-1, in which the spindle asters are positioned closer to the cortex.

The spindle pole-cortex geometry regulates the distribution and flow of cortical myosin II. (A and B) Distance between the spindle poles and the cell cortex. (A) The distance from each point on the cell periphery to the nearest spindle pole in embryos depleted of the key microtubule-bundler SPD-1/PRC1 (spd-1(RNAi)) was measured and is presented in the same way as the control embryos shown in Fig. 4 D. (B) Distance from the anterior pole (A-pole) or the posterior pole (P-pole) to the nearest cortex. Rupture of the central spindle by spd-1(RNAi) accelerated the spindle’s pole-to-pole elongation, and thus, the decrease in pole-to-cortex distance. (C and D) Effect of depletion of SPD-1 on the cytoplasmic myosin II particles. (C) Temporal color-coded trajectories of NMY-2::GFP from control (n = 22) or spd-1(RNAi) (n = 23) embryos were overlaid by maximum projection. (D) Cytoplasmic myosin II particles were tracked by automation, and the activity of the cytoplasmic transport toward the centrosomes is presented as cumulative sums after anaphase onset (see Materials and methods and Fig. S3 for more details; mean ± SEM, n = 22 and 23, respectively). (E and F) Density (E) and flow (F) of myosin II in the cell cortex. (E) Cortical myosin II (NMY-2::GFP) was quantified along the cell periphery from the anterior tip to the posterior tip and normalized with the local background and cytoplasmic levels. Average across the embryos from two sets of recordings (22 control and 23 spd-1(RNAi) embryos for 0 to 140 s p.a.o. and 56 control and 19 spd-1(RNAi) embryos for 70 to 210 s p.a.o.) were merged and are presented as a kymograph for each condition (see Materials and methods and Fig. S4 for more details). (F) The flow of myosin II along the cell periphery was computed by one-dimensional particle image velocimetry and is presented as a kymograph. The green signal indicates flow toward the posterior and the magenta toward the anterior. The timing of the transition of the cortical flow into the bidirectional mode (white dashed line) is accelerated in the embryos depleted of SPD-1, in which the spindle asters are positioned closer to the cortex.

This Feature Is Available To Subscribers Only

or Create an Account

Close Modal
Close Modal