Maintenance of undifferentiated state of stem cell precursors : the role of novel gene gone early in the Drosophila ovary 幹細胞前駆体の未分化性の維持 : ショウジョウバエ卵巣における新規遺伝子gone earlyの機能

博士論文

&nbsp;&nbsp;Many classes of sexually reproducing animals are equipped with germline stem cells (GSCs). GSCs are undifferentiated cells and have an ability to produce not only gamete but also GSCs themselves after every cell division. This self-renewal ability of GSCs allows animals to produce gamete unlimitedly to maximize success in fertilization during reproductive period. Drosophila is one of such organisms that possess GSC systems.<br/>&nbsp;&nbsp;During the larval stage, Drosophila ovary is filled with stem cell precursors, primordial germ cells (PGCs), which are kept in an undifferentiated state. At pupal stage, some of PGCs start to differentiate to oocytes/nurse cells, but the rest of PGCs are selected as GSCs and remain in an undifferentiated state. A previous study has shown that it is a crucial step to prevent PGCs from differentiation to establish adequate number of GSCs. However, how PGC differentiation is suppressed prior to GSC establishment is largely unknown.<br/>&nbsp;&nbsp;Here I show that novel gene gone early is involved in prevention of PGC differentiation. gone early encodes a putative non-peptidase. When gone early is over-expressed in PGCs in which it is endogenously expressed, PGC differentiation is excessively blocked. In contrast, in gone early mutant, the increased number of differentiating germ cells is observed and this phenotype can be rescued by expressing gone early, suggesting that gone early is responsible for the phenotype. gone early prevents PGC differentiation by means of suppressing EGF signaling, which is for the first time addressed to promote PGC differentiation in this study. In the double mutant of gone early and argos, a negative regulator of EGF signaling, the number of PGCs is much lower than in wildtype and as a consequence, the adequate number of GSCs are not established. This data demonstrates that maintaining PGCs in an undifferentiated state is prerequisite to establish the proper number of GSCs.<br/>

総研大甲第1432号