Sexually dimorphic dynamics of the microtubule network in medaka (Oryzias latipes) germ cells

Oogenesis is the process through which ovarian germ cells enter meiosis and acquire essential characteristics of an egg, such as an increase in follicular size and deposition of maternal factors. In vertebrates, however, the pathways that initiate oogenic processes after germ cell sex determination remain elusive. Here we report a dome-shaped microtubule structure that is maintained during oogenesis. This structure is established in primordial germ cells and maintained in gonocytes and stem-type germ cells in a foxl3-independent manner. dmrt1 is required for disruption of the dome structure in differentiating spermatogonia. In addition, the dome structure accumulates mitochondria and Golgi apparatus, and is replaced by the Balbiani body, an oocyte-specific aggregate producing animal-vegetal polarity, suggesting a role for this structure in organelle transfer and oocyte polarization. Our findings show the presence of a pathway regulating a sexually dimorphic microtubule network independent of germ cell feminization by foxl3. Summary StatementA dome-shaped microtubule structure leading to oocyte polarity was identified in germ cells. Genetic pathways involved in the formation and destabilization of the structure during germ cell sex determination were clarified.