Fig. 4: Mechanical feedback rescales embryonic territories.
From: Self-organized tissue mechanics underlie embryonic regulation
a–p, Model predictions (a–d and i–l) and experimental responses (e–h and m–p) to fixed and free boundary conditions in posterior epiblast halves. a,e,i,m, Sketches of the experiment (a,i) and memGFP posterior epiblast half after 3 h (e,m). b,f,j,n, Predicted and experimental profiles of contractility (magenta), tension (green) and velocity (in f and n, the black lines show the mean ± s.e.m. velocity profile from n = 19 control intact biologically independent embryos, shown in Extended Data Fig. 5b; the orange lines show n = 6 biologically independent embryos; and the blue lines show n = 13 biologically independent embryos) along the margin at t0 + 2 h. c,g,k,o, Kymographs of strain rates along the margin. d,h,l,p, Deformation maps at the end of the experiments and simulations (t0 + 3–4 h). q,r, GDF1, BRA and SOX3 mRNA in the embryos shown in e–h and m–p, respectively, fixed after live imaging. s, The size of the contracting domain in controls (black; n = 19 biologically independent embryos), attached halves (orange; n = 6 biologically independent embryos), smaller attached sectors (brown; n = 6 biologically independent embryos; see Extended Data Fig. 6a–c) and detached halves (blue; n = 13 biologically independent embryos) versus total margin length. The dotted lines show slopes of 0.37 for the controls and attached halves/sectors (R = 0.97), respectively, and 0.65 for detached halves (R = 0.90). t, Intensity profiles of the GDF1 mRNA signal along the margin in different conditions (colours are as described in s; see also Extended Data Fig. 5g for profiles of contraction, BRA and SOX3; the intensity profiles are normalized to the margin length). Data are mean ± s.e.m. u, GDF1 level versus contraction (Methods) in portions of the margin (the solid lines show the average for each condition; colours are as described in s). v, The relative size of the GDF1 domain versus the relative size of the contracted domain (Methods; R = 0.91; ***P = 0.0003, one-sided permutation test, n = 106 random permutations; colours are as described in s). Colours in c, d, g, h, k, l, o and p quantify contraction (red) and expansion (blue) as in Fig. 1. Scale bars, 1 mm (e, h, m, p, q and r).
