Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
Development. 2011 Aug;138(16):3431-40. doi: 10.1242/dev.065029. Epub 2011 Jul 13.
Asymmetric mRNA localization is an effective mechanism for establishing cellular and developmental polarity. Posterior localization of oskar in the Drosophila oocyte targets the synthesis of Oskar to the posterior, where Oskar initiates the assembly of the germ plasm. In addition to harboring germline determinants, the germ plasm is required for localization and translation of the abdominal determinant nanos. Consequently, failure of oskar localization during oogenesis results in embryos lacking germ cells and abdominal segments. oskar accumulates at the oocyte posterior during mid-oogenesis through a well-studied process involving kinesin-mediated transport. Through live imaging of oskar mRNA, we have uncovered a second, mechanistically distinct phase of oskar localization that occurs during late oogenesis and results in amplification of the germ plasm. Analysis of two newly identified oskar localization factors, Rumpelstiltskin and Lost, that are required specifically for this late phase of oskar localization shows that germ plasm amplification ensures robust abdomen and germ cell formation during embryogenesis. In addition, our results indicate the importance of mechanisms for adapting mRNAs to utilize multiple localization pathways as necessitated by the dramatic changes in ovarian physiology that occur during oogenesis.
非对称的 mRNA 定位是建立细胞和发育极性的有效机制。果蝇卵子中 Oskar 的后向定位将 Oskar 的合成靶向到后部，Oskar 在那里启动生殖质的组装。除了包含生殖细胞决定因素外，生殖质还需要定位和翻译腹部决定因素 nanos。因此，卵子发生过程中 Oskar 定位的失败会导致胚胎缺乏生殖细胞和腹部节段。通过对 Oskar mRNA 的实时成像，我们揭示了 Oskar 定位的第二个、在机制上不同的阶段，该阶段发生在卵子晚期，并导致生殖质的扩增。对两个新鉴定的 Oskar 定位因子——Rumpelstiltskin 和 Lost 的分析表明，它们专门用于 Oskar 定位的这个晚期阶段，表明生殖质的扩增确保了胚胎发生过程中腹部和生殖细胞的形成稳健。此外，我们的结果表明，在卵子发生过程中，由于卵巢生理学的巨大变化，mRNA 适应多种定位途径的机制非常重要。
