Fig. 1: TPX2 forms a co-condensate with tubulin in vitro and in the cytosol.

All scale bars are 3 μm. a Secondary structure and intrinsic disorder predictions in TPX2. b Epifluorescent image of GFP-TPX2 (green) condensates (see Supplementary Movie 1) (left) and DIC image of untagged TPX2 condensates (right), both at a final concentration of 1 µM. Representative of six experimental replicates. c Schematic for assaying phase separation—TPX2 (with or without other proteins) is purified and maintained in a high-salt (0.5 M) buffer and this is transferred at 1:4 volume:volume into a no salt buffer to achieve physiological salt levels (0.1 M). d Epifluorescent image of GFP-TPX2 (green) condensates prepared with Cy5-labeled tubulin (magenta) (both at 4 µM) prepared as shown in c and imaged in a flow chamber (see Supplementary Fig. 1d for control). Representative of six experimental replicates. e TIRF image of TPX2-Tubulin co-condensates (green and magenta, 1 and 10 µM, respectively) prepared in MT polymerization buffer in a flow chamber, 18 min after reaction started. Representative of three experimental replicates. Partition coefficients for d and e are mean values (points) with ± 1 SD as error bars from 225 and 170 condensates, respectively. f Experimental setup for g—pre-formed TPX2 condensates are overlaid with Xenopus egg cytosol containing fluorescent tubulin. g Oblique-TIRF microscopy of GFP-TPX2 (green) and tubulin (Alexa568-labeled—red) taken 5 min after reaction started (minutes:seconds). h In the same experiment as shown in Fig. 1g, the tubulin channel imaged over time (minutes:seconds) and depicted. Data representative of three experimental replicates. i Quantification of integrated tubulin signal from indicated areas corresponding to initial condensates (gray) and MT fan structures (blue). Mean values shown as circles with ± 1 SD shown as error bars from n = 5 technical replicates. Source data are provided as a Source Data file.