Fig. 5: Changes in myoplasm buckling frequency during CP initiation and expansion. | Nature Physics

Fig. 5: Changes in myoplasm buckling frequency during CP initiation and expansion.

From: Friction forces determine cytoplasmic reorganization and shape changes of ascidian oocytes upon fertilization

Fig. 5

a, Confocal images of sum intensity projections over 10 central z-slides of the myoplasm (MitoTracker Deep Red FM, top row) and cortical actin (Utrophin-Venus, bottom row) during CP morphogenesis. Arrowhead points at myoplasm buckles. Scale bar, 30 µm. b, Total length of the compacted layer of myoplasm (blue) and the underlying actin cortex (green) as a function of time after fertilization (0 min, dashed vertical line). (N = 4 animals, n = 5 oocytes.) Error bars, s.e.m. b′, Ratio of myoplasm to actin length (yellow) and the AR of the oocyte (blue; from Fig. 1b) as a function of time after fertilization (0 min, dashed vertical line). Error bars, s.e.m. c, Violin plots of the buckling frequency of the myoplasm relative to the actin cortex before fertilization (unfertilized) and at 3, 6 and 13 mpf. (N = 9 animals, n = 14 oocytes.) Solid lines, median. Dashed lines, quartiles. One-way Friedman test and Dunn’s multiple comparisons test (P = 0.2027 for unfertilized, 13 mpf; P = 0.0625 for 3–6 mpf and P > 0.9999 for 6–13 mpf; *P = 0.0127 for unfertilized 6 mpf; **P = 0.0027; ****P < 0.0001). d, Violin plots of the buckling amplitude of the myoplasm before fertilization (unfertilized) and at 3, 6 and 13 mpf. (N = 9 animals, n = 14 oocytes.) Solid lines, median. Dashed lines, quartiles. One-way analysis of variance and Holm–Sidak multiple comparisons test (*P = 0.0184, ****P < 0.0001). e, Plot of buckling of an elastic disk embedded in media of different elasticity (decreasing stiffness from solid to dashed to dotted curves) by friction forces concentrated at a distance r = a. Wavelength of vertical deflection, \(w\), as a function of r (measured from VP; r = 0) near the buckling. Inset: dependence of threshold force on rescaled mode number (buckling frequency). f, Brightfield (top row), confocal (middle row) and high-magnification (bottom row) images of the myoplasm in unfertilized oocytes during micropipette aspiration. Scale bar, 30 µm. NS, not significant.

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