XB-IMG-158550
Xenbase Image ID: 158550
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Fig. 7. Combined effects of tissue cohesion and ephrin-Eph signalling on separation. a Graphic representation of the various conditions tested in this experiment. The upper diagrams represent the various cell contacts with the tension resulting from the antagonistic action of cadherins and ephrin-Eph receptor pairs. The strength of the contact tension is also reflected in the shape of the cells (rounder outlines correspond to higher tension). The lower part of the panel summarises the impact of each manipulation on heterotypic interfacial tension and on tissue cohesion (inversely related to homotypic contact tension), and the predicted effect on separation assuming a contribution of DAH/DITH. Normal mesoderm–mesoderm contacts have low contact tension. Ephrin ectopic expression stimulates repulsion both at the explant interface and within the explant, resulting in higher tension at both homotypic and heterotypic contacts. Cadherin overexpression in the explant counteracts ephrin-induced repulsion within the explant, and to a lesser degree at the interface. Cadherin expression on the other side of the boundary decreases tension in the IMBCR, thus enhancing the difference in homotypic tension of the two tissues. EphA4 depletion (EphMO) in the explant reduces ephrin-induced repulsion within the explant (and to a lesser extent at the interface). b Result of the separation assay (graph and statistics as in Fig. 4). Ephrin-induced separation was stimulated by cadherin co-expression or Eph depletion, inconsistent with a contribution of DITH. c Simulation of maintenance of separation for each experimental condition. Energy values were based on the results shown in d. The results of the simulation were in agreement with the experimental data. d Cell–cell repulsion quantified as the hourly rate of cell detachment. Top: Diagram of the experiment. Middle: Two frames of a time-lapse confocal microscopy movie. Ectoderm and IM cells expressed, respectively, membrane Cherry and membrane GFP. The pink arrowheads point to a stable homotypic contact, the white arrowheads to a heterotypic contact that detached. Scale bar, 10 µm. Bottom: Quantification of detachments at homotypic (blue/purple and red columns) and heterotypic contacts (black columns). Statistical comparisons to ectoderm or mesoderm controls are colour coded as above Image published in: Canty L et al. (2017) © The Author(s) 2017. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution license Larger Image Printer Friendly View |