Figure 2.

The cytoplasmic-skeleton of mouse oocytes is viscoelastic. (A and B) Insets indicate that G′ quantifies the elasticity and G″ quantifies the viscous dissipation of the cytoplasmic-skeleton. The local mechanical properties (elastic and viscous) surrounding vesicles does not change from WT (blue, ○) when actin (red, □) or microtubules (magenta, ^∗) are absent. However, when myosin-V is inactivated (gray, △), the cytoplasmic-skeleton stiffens significantly (Kolmogorov-Smirnov test, p < 1 × 10⁻⁷), showing that the absence of an active actin-myosin-V meshwork leads to a stiffer mechanical environment surrounding vesicles in oocytes. (C) The ratio of the elastic and viscous moduli (G′/G″ in all oocytes shows that the cytoplasmic-skeleton is more elastic at lower frequencies and more viscous at higher frequencies with a crossover at ∼10–20 Hz. This shows the highly viscoelastic nature of the oocyte cytoplasmic-skeleton. (sample size = WT: 11 cells, 32 vesicles; Fmn2−/−: 10 cells, 33 vesicles; MyoV (−): 23 cells, 69 vesicles; Noc (1 μM): 8 cells, 52 vesicles; shaded region indicates mean ± SE. (Note: data at 10 Hz in A and B are presented in a different context in (5).) To see this figure in color, go online.