Fig. 7: FGMs tightly associate with deuterosomes and may form through Pcm1 phase separation.

a Experimental scheme. Wild-type mEPC precursors were infected with adenovirus to express GFP-Pcm1 alone (c) or together with lentivirus to co-express SNAP-Deup1 (b). SNAP-Deup1 served as deuterosome marker and its expression, controlled by the Deup1 promoter, indicated cells undergoing the centriole amplification²⁶. b FGM foci displayed liquid properties and associated with deuterosomes. Living mEPCs positive for GFP-Pcm1 and SNAP-Deup1 were imaged at 5-min intervals using a spinning disk confocal microscope. The image sequences show two fusion events of FGM foci (arrowheads). Note that the deuterosomes were associated and moved with FGM foci. 3D reconstruction was performed for the last frame to show spatial information (Supplementary Movie 6). More examples are presented in Supplementary Fig. 4. Experiment was performed once and multiple cells in different microscopic fields were live imaged. c, d FGM condensates displayed slow and limited exchanges of Pcm1 with the cytosol. mEPCs were infected to express GFP-Pcm1 as in a. GFP-positive condensates were photobleached, followed by live imaging (c). The fluorescence recovery curve (d) was from 17 condensates. Two biologically independent experiments were performed. Data are presented as mean ± s.d. e, f Secondary structure prediction and expression of Pcm1 deletion mutants. Three fragments of Pcm1 containing predicted disordered regions (e) were expressed in E. coli as His-GFP-tagged fusion proteins and purified (f). g, h Pcm1M phase-separated into liquid droplets in the presence of PEG. Purified His-GFP-Pcm1M was diluted to the indicated concentrations with or without 5% PEG3350 and imaged after incubation at 25 °C for 2 min (g). The time-lapse images (h) show the fusion of two liquid droplets (arrows). Three biologically independent experiments were performed. i, j Liquid droplets of Pcm1M rapidly exchanged the protein with the milieu. Liquid droplets prepared as in h were photobleached, followed by time-lapse imaging (i). The arrowhead points to the representative droplet before and after the photobleaching. The fluorescence recovery curve (j) was from 27 droplets. Data are presented as mean ± s.d. k Pcm1N and Pcm1C phase-separated into hydrogels. Hundred micromolar of soluble His-GFP-tagged Pcm1N or Pcm1C were topped with PBS and spun for 30 min and photographed against a white striped background to show the transparency of the pellets. After a further incubation for 20 h, the sticky pellets solidified into transparent hydrogels. Source data are provided in the Source data file.