Figure 2
From: Topographical curvature is sufficient to control epithelium elongation
The elongating epithelium shows a progressive hampering of its transversal growth. (a) Superposed outlines of a growing MDCK colony on Topo I corresponding to Movie 1. Time lapse: 20 min. (b) Longitudinal elongation of a representative MDCK colony over time. Circularity, calculated as \(\frac{4\pi \times Area}{{(Perimeter)}^{2}}\) decreases as colonies becomes less circular. Aspect ratio, calculated as the ratio of the longer axis of the bounding ellipse to the shorter axis indicates the stretching of the colony. (c) Average local velocity the colony edge outgrowth from (a), color-coded and represented on the final colony outline. (d) Velocity map of the progression of the colony edge from (a). The x axis corresponds to the local edge orientation relatively to the surface longitudinal axis. Zero degree represents the part of the edge extending in the longitudinal direction whereas 90° represent the edge extending transversally across the grooves and ridges. The black dotted lines highlight the progressing restriction of high velocity outgrowth to the edge segments extending longitudinally. (e) Representative transversally extending (left) and longitudinally extending (right) epithelium borders used for the calculation of the Protrusion Bias Index; green: actin, magenta: nuclei, yellow: colony border. Note the contrast of tortuosity between both borders on a given topography and between topographies. (f) Protrusion Bias Index as a function of convex curvature: a higher value indicates higher contrast in pluricellular protrusion formation between the colony border extending longitudinally and transversally (see Supplementary Note S1 for details). Four to 6 independent colonies for each topography (mean + SEM). A one-way ANOVA showed a statistically difference between all the topography and the Flat control, P < 0.001.
