Neither Pk1 nor Pk3 increases tissue fluidity in the gastrula ectoderm. (A) Domain structure of Pk1, Pk2, and Pk3. Note that Pk3 does not contain the STR (blue) or C4 (light green) regions. (B) Alignment of the STRs of human, mouse, Xenopus, and zebrafish Pk1 and Pk2. Conserved amino acids among both Pk1 and Pk2 (red), only Pk1 (blue), or only Pk2 (green). (C–F) Representative images of Xenopus gastrula ectoderms expressing myrGFP only (C), with Flag-Pk3 (D), with HA-Vangl2 (E), or with Flag-Pk3 and HA-Vangl2 (F). Imaging was initiated at stage 11.5. Pigmented wild-type embryos were used for image acquisition and quantification. (G–I) Quantification of cell packing according to the variation in AJ length (G), AJ linearity (H), and the number of neighboring cells (I). Statistical analyses in G and I were based on the original numeric data. One-way ANOVA was used to compare mean ranks, with the Bonferroni correction for multiple pairwise comparisons in G. The Kolmogorov‒Smirnov test was used to compare distributions in H. The chi-square test was used in I. Three embryos per group were used. The total number of cells was as follows: 281 cells and 827 AJs (myrGFP only); 191 cells and 578 AJs (Pk3 only); 329 cells and 959 AJs (Vangl2 only); and 368 cells and 1,068 AJs (Pk3 and Vangl2). n.s., not significant. (J–N) Subcellular distribution of the GFP-Pk2 mutant protein in the gastrula ectoderm. Representative images of cells expressing GFP-Pk2 (J), GFP-Pk2ΔSTR (K), GFP-Pk2ΔC4 (L), GFP-Pk2ΔVBD (M), or GFP-Pk2ΔC30 (N). Stage 11.5. myrRFP RNA was coinjected to label the plasma membrane. Scale bars: 20 μm.
