Figure 1.

Intracellular mechanics surrounding endogenous vesicles in living oocytes. (A) Mouse oocytes are large spherical cells that have a well separated cortex and cytoplasmic-skeleton composed of biopolymer filaments (bright-field image, left; scale bars, 20 μm). During prophase-I it contains a dynamic actin-myosin-V meshwork that drives vesicle motion (schematic shown in center and fluorescent image of actin filaments on right; scale bars, 5 μm). Endogenous vesicles embedded in the cytoplasmic-skeleton are trapped using optical tweezers (zoomed inset). (B) Once a vesicle is trapped, the mechanical properties of the local environment can be measured by AMR where a sinusoidal oscillating force is applied to the vesicle (blue) and the resulting displacement of the vesicle is measured (green). The viscoelastic shear modulus (G^∗) is calculated from this force-displacement measurement via the generalized Stokes-Einstein relation. (C) The mechanical properties surrounding vesicles in the cytoplasmic-skeleton of oocytes exhibits power-law behavior with frequency scaling G^∗ ∝ f^0.75. This shows that the cytoplasmic-skeleton in oocytes can be modeled as a semiflexible polymer network. To see this figure in color, go online.