Functional analysis of a novel gene, Oogenesin, which localizes to the nucleus at the time of ZGA

在本研究中，我们对卵母细胞特异性基因Ogenesin(Oog1)进行了功能分析。我们最近在小鼠胚胎中证明了Oog1在1-细胞晚期到2-细胞早期移位到细胞核。这些时期与植入前发育早期第一个基因表达的时间相吻合，这被称为合子基因激活(ZGA)。ZGA的时间取决于物种；然而，ZGA的确切机制仍不清楚。我们推测Oog1在ZGA中有一定的作用，因为Oog1在ZGA之后突然消失。首先，为了鉴定与Oog1相互作用的蛋白，我们进行了酵母双杂交实验。结果，我们鉴定了与Oog1相互作用的RalGDS和Chchd6蛋白。这些蛋白质也是母源产物，在早期发育的卵母细胞和植入前胚胎中特异表达。由于RalGDS是RAS信号转导蛋白之一，Oog1可能在RAS信号转导下发挥作用。RalGDS和Chchd6具有核定位信号，提示Oog1的核定位依赖于这些蛋白。一种新的蛋白Chchd6含有CHCH结构域，该结构域是与Oog1相互作用所必需的。RalGDS和Chchd6的表达模式与Oog1非常相似，提示这些蛋白在早期胚胎发育中的功能。此外，Oog1与Importin b和RAN以GTP依赖的方式相互作用，提示G蛋白参与了Oog1的功能。

In the present study, we performed functional analysis of oocyte-specific gene, Oogenesin (Oog1). We recently demonstrated that Oog1 translocates to the nucleus at the late 1-cell to early 2-cell stage in mouse embryos. The periods coincide with the time of the first gene expression during early preimplantation development that has been termed 'zygotic gene activation (ZGA).' The time of ZGA depends on species ; however, the precise mechanism of ZGA remains unknown. We speculate that Oog1 has some role in ZGA because Oog1 disappears suddenly after ZGA. First of all, to identify the interacting protein with Oog1, we performed yeast two-hybrid experiment. As a result, we identified RalGDS and Chchd6 protein that interact with Oog1. These proteins are also maternally derived products and express specifically in oocyte and preimplantation embryos during early development. Since RalGDS is one of the Ras signaling proteins, Oog1 may function under stream of Ras signaling. RalGDS and Chchd6 have nuclear localization signal suggesting that nuclear localization of Oog1 depend on these proteins. A novel protein Chchd6 has CHCH domain that is essential for the interaction with Oog1. The expression pattern of RalGDS and Chchd6 is quite similar with that of Oog1, suggesting the function of these protein in early embryogenesis. In addition, Oog1 interact with Importin b and Ran in GTP dependent manner, suggesting the involvement of G-protein in Oog1 function.