Fig. S4

Mechanical Modeling of Cell Shape Distributions, Related to Figure 4

(A) Log-normal fit of data (from Figure 1E) as in Figure 4A. See also Data S1, Text 6.

(B) Predicted S-D division ratio using log-normal fit in (A) and the division rule (Figure 3G).

(C) Predicted L/R distribution using log-normal fit and the division rule. A 2-peak distribution follows when cell shape changes after divisions are not considered.

(D) Local forces that mediate cell shapes. F_CM: cell-medium surface tension, F_CC: cell-cell surface tension, F_A: adhesion force, θ: transition point angle (Maître et al., 2012). See also Data S1, Text 7.

(E) Dissociated cells in Ca²⁺ free medium round up as spheres under cortical tension; adding Ca²⁺ allows them to recover adhesion to attach to dish bottom or other cells and deform from sphere.

(F) θ changes during the cell cycle in surface cells. Arrows indicate a decreased θ during and immediately after mitosis.

(G) γ as a function of time. γ values are calculated averages from measured θs of a cohort of tracked surface cells. θ is highly variable between different cells during divisions. Red arrows indicate the approximate time of cell divisions; the left-most arrow is the 2 to 4 cell division. Blue marks indicate the time points at which cell shape distributions were measured.

(H) Nocodazole treated embryos (8-cell stage treatment). The Nocodazole treated cells become more deformable. The treatment also stops cell cycles. Scale bar: 100µm.

(I) Cell shape distributions at 256-cell stage. Inset: < L/R > values (not significantly different, p = 0.38, t test on log(L/R)). σ is different (treated: 0.40, control: 0.32, p = 0.02, f-test).

(J) Surface cell morphologies at ~2k-cell+1h (green signal from mem-EYFP). Top images are 3D rendered views showing rounded edges of cdh1 MO injected cells, bottom images are cross-sections showing decreased θ (and γ). Scale bar: 30µm.

(K) Reduced flattening of cdh1 MO injected embryos in later stages by <10%. n = 60 cells from 3 embryos at each time point were measured for both groups. Error bars are SD. At ~2k-cell p = 0.096; p = 0.029; p = 0.011 (t tests on log(L/R)). σ is not different between control and MO groups (f-tests on log(L/R)).