Extended Data Fig. 5. Prewetting velocity is determined by ZO-1 binding affinity to the apical interface.

(a) Single mN-ZO-1 condensate extension dynamics after calcium switch of WT. (b) Single mN-ZO-1 condensate extension dynamics after calcium switch of ∆L27-PATJ. (c) Quantification of the elongation velocity (extension rate) of individual condensates from WT (r = 0.5 ± 0.2 µm/min) and ∆L27-PATJ (r = 0.05 ± 0.1 µm/min) after calcium switch from Fig. 4a (mean ± SD). (d) Scheme of condensate nucleation and extension in WT and ∆L27-PATJ. WT condensates nucleate and elongate along the interface with velocity v (left) recruiting ZO-1 molecules from the bulk (right) when relative binding affinity, $\mathrm{\Delta }\overline{\mathit{ϵ}}$ is larger than the threshold value, $\mathrm{\Delta }{\overline{\mathit{ϵ}}}_t$, for which the droplets do not extend. Nucleated ∆L27-PATJ condensates do not elongate, because relative binding affinity to the apical interface is too low $\mathrm{\Delta }\overline{\mathit{ϵ}}<\mathrm{\Delta }{\overline{\mathit{ϵ}}}_t$. (e) Numerical calculation of the velocity of single condensates as a function of the relative ZO-1 binding affinity to the interface region. The velocity decreases as the binding affinity decreases until it reaches zero. (f) Analytical curve for the extension velocity in a one-dimensional system as function of the binding affinity to the apical interface relative to the bulk chemical potential. (g) Snapshots of numerical solutions of concentration dynamics equation. Numerical solutions for relative binding affinity $\mathrm{\Delta }\overline{\mathit{ϵ}}=0.43$ (top), observing linear extension over time and $\mathrm{\Delta }\overline{\mathit{ϵ}}=0.19$ (bottom) with no extension. (h) Extension of multiple condensates over time with $\mathrm{\Delta }\overline{\mathit{ϵ}}=0.43$ where each extends linearly fusing into a belt. (i) Total amount of material over time of multiple condensates for $\mathrm{\Delta }\overline{\mathit{ϵ}}=0.43$ show a linear correlation. Total intensity of each condensate shown as solid-colored line and fusing shows an intensity jump reducing the curves number. (j) Table containing the parameters and values used for the numerical calculations. Panels (a, b) are representative of n = 12 condensates (c) of n = 30 condensates of n = 4 biological replicates.

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