TY - JOUR TI - Phase transitioned nuclear Oskar promotes cell division of Drosophila primordial germ cells AU - Kistler, Kathryn E AU - Trcek, Tatjana AU - Hurd, Thomas R AU - Chen, Ruoyu AU - Liang, Feng-Xia AU - Sall, Joseph AU - Kato, Masato AU - Lehmann, Ruth A2 - Hyman, Anthony A A2 - Akhmanova, Anna VL - 7 PY - 2018 DA - 2018/09/27 SP - e37949 C1 - eLife 2018;7:e37949 DO - 10.7554/eLife.37949 UR - https://doi.org/10.7554/eLife.37949 AB - Germ granules are non-membranous ribonucleoprotein granules deemed the hubs for post-transcriptional gene regulation and functionally linked to germ cell fate across species. Little is known about the physical properties of germ granules and how these relate to germ cell function. Here we study two types of germ granules in the Drosophila embryo: cytoplasmic germ granules that instruct primordial germ cells (PGCs) formation and nuclear germ granules within early PGCs with unknown function. We show that cytoplasmic and nuclear germ granules are phase transitioned condensates nucleated by Oskar protein that display liquid as well as hydrogel-like properties. Focusing on nuclear granules, we find that Oskar drives their formation in heterologous cell systems. Multiple, independent Oskar protein domains synergize to promote granule phase separation. Deletion of Oskar’s nuclear localization sequence specifically ablates nuclear granules in cell systems. In the embryo, nuclear germ granules promote germ cell divisions thereby increasing PGC number for the next generation. KW - germ cells KW - germ granules KW - mebraneless RNP granules KW - phase transition KW - Oskar protein JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -