ZFIN Image: Mongera et al., 2022, Fig. 4

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Fig. 4

Characteristic timescales of endogenous mechanical probing of the cellular microenvironment.

a, Sketches of cell protrusions and cell–cell junctions, indicating the measured time-dependent protrusion length and cell–cell junctional length, ℓp(𝑡) $ℓ_{p} (t)$ and ℓc(𝑡) $ℓ_{c} (t)$ , respectively. b, Normalized frequency of the absolute value of the protrusion strain rates, showing minimal protrusion persistence timescales in the MPZ (inset). Limitations in protrusion tracking did not allow measurement of strain rates below approximately 0.005 s⁻¹ (grey band). A-PSM (N = 1,490), P-PSM (N = 977) and MPZ (N = 391). c, Temporal autocorrelation of cell–cell junction length in different regions of the tissue along the AP axis, showing persistence (autocorrelation) timescales of approximately 1 minute (inset). Error bars, s.e.m. d, Fourier transform (FT) mode amplitudes of the time evolution of junction length in the tissue for different regions along the AP axis, showing a peak at frequencies (red line) of approximately 0.5 min⁻¹. N of approximately 3,500 junctions in A-PSM and P-PSM (four embryos) and 7,896 junctions in MPZ (three embryos) in c and d. Error bars, s.e.m. e–h, Confocal sections of MPZ and PSM tissue regions in embryos with myosin II and membrane labels (e) and in embryos with actin (Utrophin, UTR) and membrane labels (g). Scale bars, 50 µm. Zoomed in yellow rectangular regions shown on right. Highlighted yellow region corresponds to analysis region around cell–cell contact. Scale bars, 10 µm. Measured myosin II (f) and actin (h) signal autocorrelations and the characteristic timescales for myosin II (f, inset) and actin (h, inset) dynamics. N = 12 and two embryos for each condition (MPZ, PSM, actin and myosin II). Error bars, s.e.m. (e,f). i, Simulated tissue dynamics arising from actomyosin-generated tension dynamics at cell–cell contacts (Methods). j, Predicted ratio of cell–cell contact length persistence timescale 𝜏ℓ $τ_{ℓ}$ and tension persistence timescale τ_T, in terms of the ratio between the tension persistence timescale τ_T and the dissipation timescale τ_D. Measured values of these ratios in MPZ (light blue square) and PSM (violet square) are shown. Error band of simulation data (s.d.; N = 6 temporal correlations) and s.e.m. of experimental data are shown.

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