The α-Cat M region is essential for adhesion during mesoderm invagination and germband extension. (A) Quantification of mesoderm invagination defects in embryos of indicated genotype. Color-coded example images are given at right. Orange lines indicate edges of mesoderm. Red, open ventral furrow; yellow, partially fused ventral furrow; indigo, >90% midline fusion. Scale bar; 100 μm. (B) Quantification of defects in the lateral ectoderm during germband extension in embryos of indicated genotype. Classification used: indigo, wild type, very few gaps seen; cyan, small gaps; yellow, large gaps or tears; red, few if any identifiable AJs. Pink areas represent regions of gaps where apical junctions have lost contact, plotted in C. Scale bar, 10 μm. (C) Area of gaps in α-Cat-RNAi α-CatX embryos. n is the sum of all gap areas within a field of view per embryo (e). (D) Plot showing the angle of the major axis of ellipses fitted to each gap in α-Cat-RNAi α-CatX embryos. N = number of embryos (e), 90° = DV axis. (E) Extension of the germband observed over 40 min in α-Cat-RNAi α-CatX embryos. Change in length from proctodeal invagination to posterior is normalized to total embryo length; n = number of embryos analyzed (e). For C and E, height of bars represent mean, error bars represent SD. Significance determined by Kruskal–Wallis test with Dunn’s multiple comparisons test (C), and ordinary one-way ANOVA with Tukey’s multiple comparisons test (E; **** = P < 0.0001, *** = P < 0.001, ** = P < 0.01, * = P < 0.05).