Oil droplets recapitulate nucleus behavior. (A) Visualization of F-actin in the region of the nucleus (upper panels) and of the droplet (lower panels) observed in the same oocyte in two different Z planes. F-actin is labeled with GFP-UtrCH, which is either highly expressed (left panels) or mildly expressed (right panels). The square-dashed region is enlarged in the right panel for each condition of GFP-UtrCH expression. F-actin is in white. Scale bars are 10 µm. One experiment. (B) Quantification of the ratio of the GFP-UtrCH fluorescence intensity for the nucleus versus the cytoplasm (green dots) and for the oil droplet versus the cytoplasm (red dots) from A. F-actin is in black. The dotted green line and red line overlays on the fluorescent images depict how the different fluorescence intensities were measured (see also Materials and methods). A Kolmogorov-Smirnov test resulted in a nonsignificant (ns) difference between the two distributions (P = 0.28). Scale bar is 10 µm. (C) The distributions of the radial velocities of the nucleus centroid and of the oil droplet centroid as a function of the distance to oocyte center are comparable. Red: Radial velocity of oil droplet centroid for droplets with a diameter between 20 and 30 µm. n = 6 oocytes. Green: Radial velocity of nucleus centroid for Fmn2^−/− oocytes injected with Formin 2 from Almonacid et al. (2015). Mean and standard deviation are superimposed; three independent experiments.