Interaction between Polo and BicD proteins links oocyte determination and meiosis control in Drosophila

Meiosis is a specialized cell cycle limited to the gametes in Metazoa. In Drosophila, oocyte determination and meiosis control are interdependent processes, and BicD appears to play a key role in both. However, the exact mechanism of how BicD-dependent polarized transport could influence meiosis and vice versa remains an open question. In this article, we report that the cell cycle regulatory kinase Polo binds to BicD protein during oogenesis. Polo is expressed in all cells during cyst formation before specifically localizing to the oocyte. This is the earliest known example of asymmetric localization of a cell-cycle regulator in this process. This localization is dependent on BicD and the Dynein complex. Loss- and gain-of-function experiments showed that Polo has two independent functions. On the one hand, it acts as a trigger for meiosis. On the other hand, it is independently required, in a cell-autonomous manner, for the activation of BicD-dependent transport. Moreover, we show that Polo overexpression can rescue a hypomorphic mutation of BicD by restoring its localization and its function, suggesting that the requirement for Polo in polarized transport acts through regulation of BicD. Taken together, our data indicate the existence of a positive feedback loop between BicD and Polo, and we propose that this loop represents a functional link between oocyte specification and the control of meiosis.     

Electrical properties of vertebrate oocyte membranes

The electrical properties of vertebrate oocyte and egg cell membranes are reviewed. Ion channels of these oocytes generate transcellular currents and action potentials as well as responses to neurotransmitters. Electrical properties change during meiotic maturation and fertilization. Available information about the electrical properties of sperm is also discussed.     

CDK2在精母细胞和卵母细胞减数分裂中的作用

细胞周期蛋白依赖性蛋白激酶(Cyclin-dependent kinase,CDK)2是驱动细胞通过G1/S期检验点进入S期完成DNA合成的关键性调控蛋白.过去一度认为CDK2在减数分裂中的作用不像在有丝分裂中那么重要.直至2003年在敲除小鼠CDK2基因后出乎意料地发现小鼠生长发育正常,只是不育:生殖细胞减数分裂受到影响.这一发现引起人们重新审视CDK2在细胞增殖中的作用,对CDK2在减数分裂中的作用研究受到关注,本文就此作一综述.     

Cohesion介导的减数分裂异常与卵子老化发生的关系

社会发展及计划生育政策的顺势改变,使得高龄女性的生育需求不断扩大,但与年龄相关的卵子老化是高龄女性急需解决的生育难题,而造成卵子老化的主因确是卵母细胞非整倍体发生率的增加.粘连蛋白(cohesin)能够介导姐妹染色单体之间的着丝粒凝聚力从而稳定二价染色体结构,cohesin介导的减数分裂异常与卵子老化的发生关系密切,以...     

mos gene transforming efficiencies correlate with oocyte maturation and cytostatic factor activities.

The mos proto-oncogenes from different vertebrate species transform mouse NIH 3T3 cells with markedly different efficiencies. v-mos, mouse (c-mosmu), and chicken (c-mosch) mos transform NIH 3T3 cells 10- to 100-fold more efficiently than do human (c-moshu) and Xenopus (c-mosxc) mos. The mos genes with the highest transforming activity efficiently induce maturation in Xenopus oocytes and mimic cytostatic factor (CSF) by causing mitotic cleavage arrest in embryos. Chimeric v-mos/c-moshu proteins that had high transforming efficiencies in NIH 3T3 cells were also effective in the induction of oocyte maturation and CSF cleavage arrest. We measured the in vitro autophosphorylation activities of the different mos proteins and found that the levels of kinase activity of v-mos, c-mosmu, and c-mosch were much higher than that of c-mosxc. These data indicate that mos gene transforming efficiency and the ability to induce oocyte maturation or mimic CSF activity are correlated with in vitro autophosphorylation activity and suggest that the mos protein plays a similar role in transformed cells and normal oocytes.     

Stimulation and inhibition of rat oocyte meiosis by forskolin

The adenylate cyclase activator forskolin was used to study the role of cAMP for oocyte meiosis and follicular steroid secretion. Follicular and cumulus cAMP production was stimulated dose-dependently by forskolin, as was the follicular secretion of progesterone, testosterone and estradiol. Forskolin induced meiosis in follicle-enclosed oocytes with a maximal effect at 1 microM, with lower and higher concentrations being less effective. The spontaneous resumption of meiosis in isolated cumulus-enclosed oocytes was dose-dependently retarded by forskolin. Meiosis of cumulus-free oocytes was also retarded but only slightly. These data support the earlier hypothesis that a limited increase in follicular cAMP levels triggers meiosis, whereas sustained levels of cAMP in the oocyte itself prevent meiosis.     

The control of vertebrate pests by vertebrate predators

Carnivores can control mammalian pests for long periods, but only after pest numbers have been reduced by other means. In Australia, the cause is prolonged dry weather. The consequent low populations of rabbits can then be regulated by European foxes, feral cats and dingoes. Kangaroos, and probably feral goats and pigs, succumb to dingoes at the same time, as substitute prey for rabbits. In the general case, such regulatory predation may be triggered climatically, by disease or by human intervention. When predators are themselves pests to be controlled, integrated pest management may be required to avoid unwanted resurgences of other pests.     

The effects of proteasome inhibitor lactacystin on mouse oocyte meiosis and first cleavage

In order to study the effects of ubiquitin-proteasome pathway (UPP) on mouse oocyte meiosis and cleavage, oocytes undergoing maturation and parthenogenetic activation and 1-cell embryos were treated with lactacystin, a specific inhibitor of proteasome. The results indicated that the rate of GVBD was not influenced by the treatment, but polar body extrusion, parthenogenesis and first cleavage were inhibited. Immunofluorescent staining using anti β-tubulin antibody indicated that the continuous treatment of lactacystin from GV stage disorganized microtubules and spindle assembly. When metaphase stage oocytes were treated with the drug, the already formed spindle structure was not affected, but the oocytes were arrested at metaphases. The 1-cell embryos were arrested at interphase or metaphase of first mitosis when they were incubated in the drug. Proteasome regulatory subunit PA700 was located in the spindle region, as indicated by immunofluorescence. These results suggest that UPP has effects on the process of oocyte meiosis and early cleavage in many aspects, including normal organization of spindle at prophase and segregation of chromosomes at anaphase for normal meiosis.     

The mitogen-activated protein kinase signaling pathway stimulates mos mRNA cytoplasmic polyadenylation during Xenopus oocyte maturation

The Mos protein kinase is a key regulator of vertebrate oocyte maturation. Oocyte-specific Mos protein expression is subject to translational control. In the frog Xenopus, the translation of Mos protein requires the progesterone-induced polyadenylation of the maternal Mos mRNA, which is present in the oocyte cytoplasm. Both the Xenopus p42 mitogen-activated protein kinase (MAPK) and maturation-promoting factor (MPF) signaling pathways have been proposed to mediate progesterone-stimulated oocyte maturation. In this study, we have determined the relative contributions of the MAPK and MPF signaling pathways to Mos mRNA polyadenylation. We report that progesterone-induced Mos mRNA polyadenylation was attenuated in oocytes expressing the MAPK phosphatase rVH6. Moreover, inhibition of MAPK signaling blocked progesterone-induced Mos protein accumulation. Activation of the MAPK pathway by injection of RNA encoding Mos was sufficient to induce both the polyadenylation of synthetic Mos mRNA substrates and the accumulation of endogenous Mos protein in the absence of MPF signaling. Activation of MPF, by injection of cyclin B1 RNA or purified cyclin B1 protein, also induced both Mos protein accumulation and Mos mRNA polyadenylation. However, this action of MPF required MAPK activity. By contrast, the cytoplasmic polyadenylation of maternal cyclin B1 mRNA was stimulated by MPF in a MAPK-independent manner, thus revealing a differential regulation of maternal mRNA polyadenylation by the MAPK and MPF signaling pathways. We propose that MAPK-stimulated Mos mRNA cytoplasmic polyadenylation is a key component of the positive-feedback loop, which contributes to the all-or-none process of oocyte maturation.     

The effects of proteasome inhibitor lactacystin on mouse oocyte meiosis and first cleavage

Many studies have shown that the ubiq-uitin-proteasome pathway (UPP) for the degradation of short-lived proteins plays a key role in regulating cell cycle progression[1—3]. At least two distinct prote-olytic pathways are required for cell cycle process. The first pathway promotes transition from G1 to S phase, and the second initiates the onset of anaphase and exit from mitosis. The inhibition of UPP will re-sult in the blockage of cell cycle process. The knowl-edge of the role of UPP in…     

Lead cations affect the control of both meiosis arrest and meiosis resumption of the mouse oocyte in vitro at least via the PKC pathway

The aim of this study was to determine in vitro whether lead has a direct cytotoxic effect on the female gamete or through its surrounding somatic cells. We had previously demonstrated that it partly accumulates in the mouse ovary and induces follicle and oocyte apoptosis. The data reported here demonstrate for the first time that low levels of Pb(NO3)2 (相似文献   

Unique effects of spindle inhibitors on mammalian oocyte meiosis

The effects of Nocodazole, reported to be a rapidly reversible inhibitor of microtubules in somatic cells (1), and Colcemid, a classic microtubule inhibitor, were studied for their effects on mouse and cow oocyte in vitro meiotic resumption. When present throughout the maturation period to Metaphase II/Polar Body I, both compounds predictably inhibited progression at Metaphase I (MI). An unexpected effect was seen on mouse germinal vesicle breakdown (GVB) with both inhibitors, but not in cow oocytes tested with Nocodazole. Recovery from Nocodazole was notably retarded in mouse oocytes even with brief exposure times. Addition of 1 microgram/ml of Nocodazole 10 min after commencement of mouse and cow oocyte incubation was sufficient time to allow normal GVB, while inhibition at MI still took place suggesting that the critical events of GVB occur very quickly in vitro.     

Influence of follicular components on oocyte meiosis in vitro

Oocytes and follicular components obtained from ovaries recovered from mature Hereford cows at slaughter were used to determine follicular influence on oocyte maturation. Some oocytes were fixed immediately to determine the stage of maturation. The remaining oocytes were cultured for 32 to 34 hr in various environments to determine the influences of the granulosum and follicular fluids on meiotic changes. All noncultured oocytes had dictyate nuclei except one in premetaphase. Oocytes cultured in 50 or 100% follicular fluid or in contact with stratum granulosum cells showed some meiotic inhibition both before and after germinal vesicle breakdown (GVB). The least resumption of meiosis occurred in oocytes cultured in their intact follicles.     

Nicotine alters bovine oocyte meiosis and affects subsequent embryonic development

The effects of nicotine on nuclear maturation and meiotic spindle dynamics of bovine oocytes and subsequent embryonic development were investigated. Maturation rates (85%-94%) derived from nicotine treatments at 0.01 to 1.0 mM were similar to the control (86%), but significantly decreased at 2.0 to 6.0 mM. Haploid complements of metaphase II oocytes in 0.01 to 1.0 mM nicotine (approximately 90%) were similar to the control, while lower (ranged from 63% to 76%, P < 0.05 or P < 0.01) haploid oocytes were observed in the 2.0 to 6.0 mM nicotine groups. The majority of the PB1-free oocytes derived from 3.0 to 6.0 mM nicotine treatments were diploidy (2n = 60). Spindle microtubules changed from characteristically being asymmetrical in the controls to being equally distributed into two separate chromosome groups in the nicotine treatments. Nicotine disorganized the microfilament organization and inhibited the movement of anaphase or telophase chromosomes to the cortical area. The inhibited two chromosome groups became two spindles that either moved close in proximity or merged entirely together resulting in diploidy within the affected oocyte. Nicotine treatment significantly reduced the rate of cleavage and blastocyst development after parthenogenetic activation. Diploidy and cell number were drastically reduced in the resultant blastocysts. In conclusion, nicotine can alter the normal process of bovine oocyte meiosis and affects subsequent embryonic development.