Supplementary Materials

A tensile ring drives tissue flows to shape the gastrulating amniote embryo

Mehdi Saadaoui, Didier Rocancourt, Julian Roussel, Francis Corson, Jerome Gros

Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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  • Materials and Methods
  • Supplementary Text
  • Figs. S1 to S20
  • Table S1
  • Captions for Movies S1 to S14
  • References

Images, Video, and Other Media

Movie S1
PIV analysis of a single memGFP embryo cultured ex vivo.Left: Time-lapse movie of a memGFP transgenic embryo (acquisition every 6 min for 10 h) overlaid with trajectories reconstructed by PIV (top; 2 h sliding window) and automatically identified prospective primitive streak (magenta) and EP (green) territories (bottom). Right: Deformation map. Colors show area changes (blue, expansion; red; contraction) in the initial (top) and current (bottom) configurations of the tissue.
Movie S2
Spatiotemporal registration of 6 control embryos into a reference average embryo. Time-lapse movies of n = 6 memGFP transgenic embryos (acquired every 6 min and registered from t = t0 to t = t0 + 8 h) overlaid with automatically identified prospective primitive streak (magenta) and EP (green) territories (upper row), and the corresponding trajectories (middle row) and deformation maps (bottom row). The last column shows the average embryo constructed from these individual embryos.
Movie S3
PIV analysis of a single memGFP embryo imaged directly in the egg.Left: Time-lapse movie of a memGFP transgenic embryo (acquisition every 6 min for 9 h, directly from a windowed egg) overlaid with trajectories (top; 2 h sliding window) and automatically identified prospective primitive streak (magenta) and EP (green) territories (bottom). Right: Deformation map. Colors show area changes (blue, expansion; red; contraction) in the initial (top) and current (bottom) configurations of the tissue.
Movie S4
Analysis of tissue flows in the average embryo. From left to right: Deformation map, velocity field decomposed into divergent and rotational components, and apparent forces (negative of the Laplacian of the velocity field).
Movie S5
Quantitative model of gastrulation.Left: Experimental trajectories and deformation map for the average embryo. Right: Trajectories and deformation map for the model, as fit to the average embryo. Tissue flow in the model is driven by area changes, taken from experiment, and active tensions along the margin (represented by a magenta line for legibility; the margin has a finite width as in Movie S6).
Movie S6
Synthetic model of gastrulation.Top: time evolution of EE expansion (left, blue), areal contraction of the prospective primitive streak (center, red), and tension along the margin (right, magenta) as a function of space and time used to build a synthetic model of gastrulation. Patterns of areal expansion and contraction, defined relative to the initial configuration of the tissue (as displayed in Fig. S3A), are shown here in its current configuration, where they take effect. Notice in particular that the initially crescent-shaped prospective primitive streak (cf. Fig. S3A) has undergone substantial convergent extension before areal contraction sets in. Bottom: the resulting trajectories (left) and deformation map (right).
Movie S7
Estimation of tissue strain using UV-laser cuts in control embryos.Left: Time-lapse movie of a control embryo imaged for 6 h, overlaid with automatically detected margin (dashed line) and apparent forces (arrows), used to position the cuts. 52 Right: 250 μm laser cuts were then sequentially performed in the posterior margin (red square), anterior margin (green square), and EP (blue square) . Note the anisotropic relaxation at the margin but not in the EP.
Movie S8
Formation of a large-scale supracellular actomyosin ring at the margin. Time-lapse movie of a hUbc:Lifeact-NeonGreen_ires_tdTomato-Myl9 transgenic embryo (acquisition every 6 min for 8 h, tdtomato-Myl9 only). Only the right side has been imaged (tiled and stitched), with a 40x objective. The red and blue boxes show higher magnification at the posterior and anterior margin, respectively. Red arrows point at supracellular MyosinII cables progressively developing from the posterior and to the anterior margin of the embryo. The last image is a projection of the last 10 time points to reveal tissue flows.
Movie S9
MyosinII dynamics and concomitant cell behavior at the margin. Time-lapse movie of a hUbc:Lifeact-NeonGreen_ires_tdTomato-Myl9 transgenic embryo (acquisition every 6 min for 90 min, tdtomato-Myl9 only) at the anterior and posterior margin (upper and lower panel respectively). A few cells have been tracked (colored dots and masks) to highlight i) the tangential extension of supracellular myosin cables and concomitant cell elongation and oriented division, at the anterior margin; ii) contraction of supracellular myosin cables and cell apical surface at the posterior margin.
Movie S10
Cell dispersion in control and drug-treated embryos. Time-lapse movie of memGFP transgenic embryos (acquisition every 5 min for 90 min) in control, HU only, HU+Q-VD-OPh, and Q-VD-OPh only, highlighting the effect of cell division and/or apoptosis inhibition on cell rearrangements and subsequent cell dispersion as revealed by segmenting columns of cells (colored masks). Note that whereas HU alone stabilizes epithelial toplogy it induces apoptosis-mediated extrusion of epithelial cells. In contrast, the combination of HU and Q-VD-OPh prevents cell extrusion and greatly stabilizes epithelial topology, whereas Q-VD-OPh only has no noticeable effect on its own on epithelial topology.
Movie S11
Spatiotemporal registration of 5 HU+Q-VD-OPh treated embryos into an average embryo. Time-lapse movies of memGFP transgenic embryos treated with HU+Q-VD-OPh (acquired every 6 min and registered from to t = t0 to t = t0 + 8 h) overlaid with automatically detected EP territory (green; upper row), and the corresponding trajectories (middle row) and deformation maps (bottom row). The last column shows the average embryo constructed from these individual embryos.
Movie S12
Analysis of tissue flows in HU+Q-VD-OPh- treated embryos. From left to right: Deformation map, velocity field decomposed into divergent and rotational components, and apparent forces (negative of the Laplacian of the velocity field).
Movie S13
Estimation of tissue strain using UV-laser cuts in HU+Q-VD-OPh treated embryos.Left: Time-lapse movie of a HU+Q-VD-OPh-treated embryo imaged for 6 h, , overlaid with automatically detected margin (dashed line) and apparent forces (arrows), used to position the cuts Right: 250 μm laser cuts were then sequentially performed in the posterior margin (red square), anterior margin (green square), and EP (blue square). Note the anisotropic relaxation at the margin but not in the EP, as in a control embryo, whereas the apparent forces (negative of the Laplacian of the velocity field) is greatly reduced (compare with Movie S7), arguing for an increase in viscosity.
Movie S14
Response to altered boundary conditions. Predictions from the synthetic model for the response to centered (left) and off-centered (right) cuts that generate a new tissue border, alongside with the experimental response following a laser cut. Top row: schematic of experiment and time-lapse movie of memGFP embryo, overlaid with automatically identified prospective primitive streak (magenta) and EP (green) territories. Middle row: rotational component of the velocity field. Bottom row: deformation map.