Figure 1.

Liquid–liquid phase separation of FUS.A, structural feature of FUS protein. FUS comprises of, from N- to C-terminus, one QGSY-rich region, one Gly-rich domain, one RRM, two RGG domains interspaced with a single Zn finger, and Pro-/Tyr-rich region (PY) containing NLS. Low-complexity (LC) intrinsically disordered regions are indicated below the structural map. B, SDS-PAGE pattern of the purified FUS protein. Two micrograms of the purified proteins was analyzed, in parallel with the marker protein mixture, by 10% SDS-PAGE, and the gel was stained with Coomassie brilliant blue. C, protein concentration-dependent increase of the formation of FUS condensates. The FUS condensates formed were observed by phase-contrast microscopy (scale bar, 20 μm). High-magnification images are shown in Figure S1. The y-axis shows the level of turbidity and the standard errors (±SEM) obtained after three independent experiments. Measurements were performed after incubating for 30 min at 25 °C. Samples of 16 μM and above were measured at 5-fold dilution. The red arrowheads indicate the condensates during fusion. D, average diameters of the FUS condensates formed at 2 μM FUS concentration. The size of FUS condensates was measured from the microscopic images. One typical high-magnification image is shown on the bottom.