Fig. 2: Pole relaxation with equatorial activation induces fast and symmetric division.
a Schematic of light activation patterns. (i) Global activation within the entire liposomes. (ii) Local activation at the equatorial plane. (iii, iv) Pole relaxation by dissociating the actin cortex at the poles using a high-power 405 nm laser. b Snapshots showing the endpoint images of post-deformed liposomes exposed to different light-activation modes. c Aspect ratio over time (n = 20 liposomes and N = 4 independent experiments in global; n = 18 and N = 5 in local; n = 30 and N = 5 in global + pole; n = 39 and N = 4 in local + pole). d Boxplot showing maximum aspect ratio in (c). e Schematic showing the definition of the asymmetry parameter \({P}_{{{{\rm{act}}}}}\). The asymmetry parameter approaches 1 for asymmetric and 0 for symmetric actin distribution. The integral is taken along the membrane contour \({ds}\). f Phase diagram of maximum aspect ratio and asymmetry parameter (n = 20 liposomes and N = 4 independent experiments in global; n = 18 and N = 5 in local; n = 30 and N = 5 in global + pole; n = 39 and N = 4 in local + pole). Small points represent individual liposome. Large symbols are mean ± SD. Significance (*) is based on Fisher’s exact test between ‘local + relax.’ and ‘global + relax.’ with \({P}_{{{{\rm{act}}}}} \, > \, 0.25\) classified as asymmetric \({P}_{{{{\rm{act}}}}} \, < \, 0.25\) as symmetric. g and h Furrow radius over time normalized by its initial value, comparing different light activation patterns (g) (n = 28 liposomes and N = 9 independent experiments in global + pole; n = 40 and N = 9 in local + pole) and comparing local activation + pole relaxation with cofilin or Arp2/3 (h) (n = 40 liposomes and N = 9 independent experiments in control; n = 39 and N = 7 in cofilin; n = 20 and N = 7 in Arp2/3). The dashed line is a guide for furrow speed fitting within 0 to 1.2 min. i Boxplot showing minimum furrow radius in (g) and (h) (n = 28 liposomes and N = 9 independent experiments in global + pole; n = 40 and N = 9 in control; n = 39 and N = 7 in cofilin; n = 20 and N = 7 in Arp2/3). j Boxplot showing furrowing speed calculated from the linear fitting to the furrow radius time course within 0 to 1.2 min in (g) and (h) (n = 28 liposomes and N = 9 independent experiments in global + pole; n = 40 and N = 9 in control; n = 39 and N = 7 in cofilin; n = 20 and N = 7 in Arp2/3). Cofilin, Arp2/3, and His-VCA were used at 0.15 µM, 18 nM, and 1.5 µM, respectively. Data are presented as mean ± SD (c, f–h) or boxplots where the interquartile range (IQR) is between Q1 (25th percentile) and Q3 (75th percentile), the center line indicates the median, whiskers are extended to Q3 + 1.5 × IQR and Q1 − 1.5 × IQR (d, i, j); *p < 0.05; **p < 0.01; ***p < 0.001 in a two-sided Wilcoxon rank sum test. n.s., not significant. Scale bars, 10 μm. Source data are provided as a Source Data file.
