Wang Shufang, Hu Jianjun, Guo Xinzheng, Liu Johne X, Gao Shaorong
National Institute of Biological Sciences (NIBS), College of Life Science, Beijing Normal University, Beijing, People's Republic of China.
Biol Reprod. 2009 Mar;80(3):555-62. doi: 10.1095/biolreprod.108.073197. Epub 2008 Nov 12.
Mouse oocytes undergo two successive meiotic divisions to generate one large egg with two small polar bodies. The divisions are essential for preserving the maternal resources to support embryonic development. Although previous studies have shown that some small guanosine triphosphatases, such as RAC, RAN, and CDC42, play important roles in cortical polarization and spindle pole anchoring, no oocytes undergo cytokinesis when the mutant forms of these genes are expressed in mouse oocytes. Here, we show that the ADP-ribosylation factor 1 (ARF1) plays an important role in regulating asymmetric cell division in mouse oocyte meiosis. Microinjection of mRNA of a dominant negative mutant form of Arf1 (Arf1(T31N)) into fully grown germinal vesicle oocytes led to symmetric cell division in meiosis I, generating two metaphase II (MII) oocytes of equal size. Subsequently, the two MII oocytes of equal size underwent the second round of symmetric cell division to generate a four-cell embryo (zygote) when activated parthenogenetically or via sperm injection. Furthermore, inactivation of mitogen-activated protein kinase (MAPK) but not MDK (also known as MEK) has been discovered in the ARF1 mutant oocytes, and this further demonstrated that ARF1, MAPK pathway plays an important role in regulating asymmetric cell division in meiosis I. Similarly, ARF1(T31N)-expressing, superovulated MII oocytes underwent symmetric cell division in meiosis II when activation was performed. Rotation of the MII spindle for 90 degrees was prohibited in ARF1(T31N)-expressing MII oocytes. Taken together, our results suggest that ARF1 plays an essential role in regulating asymmetric cell division in female meiosis.
小鼠卵母细胞经历两次连续的减数分裂，产生一个大的卵子和两个小的极体。这些分裂对于保存母体资源以支持胚胎发育至关重要。尽管先前的研究表明，一些小的鸟苷三磷酸酶，如RAC、RAN和CDC42，在皮质极化和纺锤体极锚定中起重要作用，但当这些基因的突变形式在小鼠卵母细胞中表达时，没有卵母细胞进行胞质分裂。在这里，我们表明ADP-核糖基化因子1（ARF1）在调节小鼠卵母细胞减数分裂中的不对称细胞分裂中起重要作用。将Arf1显性负突变体形式（Arf1(T31N)）的mRNA显微注射到完全成熟的生发泡卵母细胞中，导致减数分裂I中的对称细胞分裂，产生两个大小相等的中期II（MII）卵母细胞。随后，当通过孤雌激活或精子注射激活时，两个大小相等的MII卵母细胞进行第二轮对称细胞分裂，产生一个四细胞胚胎（合子）。此外，在ARF1突变体卵母细胞中发现有丝分裂原激活蛋白激酶（MAPK）而非MDK（也称为MEK）失活，这进一步证明ARF1-MAPK途径在调节减数分裂I中的不对称细胞分裂中起重要作用。同样，当进行激活时，表达ARF1(T31N)的超排卵MII卵母细胞在减数分裂II中进行对称细胞分裂。在表达ARF1(T31N)的MII卵母细胞中，MII纺锤体旋转90度被阻止。综上所述，我们的结果表明ARF1在调节雌性减数分裂中的不对称细胞分裂中起重要作用。
