Fig. 3: Computational models predict cytoplasmic forces to be predominant drivers of nuclear condensate remodeling.

a Effective diffusion coefficients normalized by droplet size and droplet diffusive exponents \(\alpha\) from SRSF2-GFP experiments (NSN oocytes) and simulations with NSN-like obstacles; droplet number, Experiment = 46; Simulation = 115; violin plots with median±quartiles; P values derived from two-tailed Mann–Whitney U-tests, ns not significant, P = 0.1203 and P = 0.8741. b Droplet number (left) and size (right) evolution in NSN-like simulations (lines) and in NSN-oocyte experiments (circles) for Control, Nocodazole, and FMN2^−/− conditions; simulations and experiments were aligned on comparable time frames by defining 45 droplets as t = 0; simulations performed five times per condition and experimental data from four NSN oocytes per condition. c Nuclear droplet coalescence speed per hour relative to droplet number decrease in experimental NSN conditions (Control in blue, Nocodazole in green, and FMN2^−/− in dark blue) and computational models with simulated NSN Control-like, Nocodazole-like, and FMN2^−/−-like cytoplasmic activity; error represents mean ± 95% confidence interval; the number of experimental measurements, Control NSN = 9, Nocodazole = 9, FMN2^−/− = 7; 5 simulations per condition. d Schematic representation of the NSN-to-SN-like simulation regime; first 12 h of simulations are performed with the same parameters as in NSN-like simulations; nuclear obstacle and cytoplasmic stirring activity switch occur at 12 h whereby 40% of chromatin-like obstacles surround the nucleolus and cytoplasmic activity is nearly doubled to mimic the transition into the SN-like condition, physiologically marked by chromatin condensation and cytoplasmic force intensification. e 3D-simulations (n = 41) showing nucleoplasmic SRSF2 droplet coalescence speed on an hour-to-day timescale relative to cytoplasmic forces (intensities colored according to the gradient on the left); simulations start from an NSN-like nucleus state with 45 SRSF2 droplets; chromatin condensation and cytoplasmic activity intensification, simulating the transition into late growth, occurs at 12 h. f Time frames of 3D-simulations in (e) with a gradient of starting point cytoplasmic intensities that include the FMN2^−/−-like and Control-like scenarios; nuclear speckles (SRSF2⁺ droplets) are orange, and a gray nucleolus is depicted in a nucleus-like container. Color codes based on cytoplasmic stirring intensities; scale bar, 5 μm. Source data are provided as a Source Data file.