Cytoplasmic volume contributes to nuclear size scaling in X. laevis embryo extracts. (A) Top: Schematic diagram of the experimental approach. Stage 10–10.5 embryos were arrested in late interphase with cycloheximide. Embryonic extract containing endogenous nuclei was encapsulated in droplets using microfluidic devices. Nuclei were visualized by uptake of GFP-NLS. Bottom left: In vivo nuclear size scaling data for X. laevis stages 8 to 10.5 (Jevtić and Levy, 2015). Bottom right: Blue and orange represent cytoplasm and nuclei, respectively. (B) Spherical extract droplets were incubated at room temperature. (C) Spherical droplet data. At each time point, 18–104 nuclei were quantified (57 nuclei on average). Each curve corresponds to a different extract. (D) Flattened droplet data. The ratio of the long axis to the short axis was on average ∼1.7. At each time point, 10–117 nuclei were quantified (35 nuclei on average). Each curve corresponds to a different extract. (E) The fold change in nuclear volume was calculated by dividing maximum nuclear volume by initial nuclear volume at t = 0. Best-fit logarithmic regression curves are displayed. For each time point of each experiment, 7–311 nuclei were quantified (63 nuclei on average). Data are shown for 26 different spherical droplet volumes (blue) and 12 different flattened droplet volumes (orange), using 23 different extracts. Error bars represent SD.