Control of Oocyte Maturation in C. elegans

卵母细胞成熟和排卵是有性生殖所必需的生物学过程。 在卵母细胞成熟过程中，由于Cdc 2/CyclinB蛋白激酶、成熟促进因子（MPF）的激活，卵母细胞从前期进入减数分裂M期。 在许多物种中，激素触发促进卵母细胞成熟和排卵的信号转导级联，但一个主要的悬而未决的问题涉及详细的分子机制。 如果不能正确调节这一关键的减数分裂细胞周期转换，可能导致不育、流产或唐氏综合征。 促进哺乳动物卵母细胞成熟的信号尚不清楚，成熟诱导物质的受体尚未在任何生物体中鉴定。 为了补充在脊椎动物中的研究，我们正在使用线虫秀丽隐杆线虫作为研究通过细胞间信号传导控制卵母细胞成熟和排卵的模型。 我们的研究表明，精子细胞骨架蛋白，主要精子蛋白（MSP），是一个双向信号，促进卵母细胞成熟和性腺鞘细胞收缩在C。优雅 我们已经表明，MSP结合卵母细胞和激活保守的MAP激酶级联。我们的研究结果表明，MSP结合卵母细胞需要VAB-1 Eph受体酪氨酸激酶和高度保守的Hem家族蛋白，SIM-2的功能。 MSP信号转导导致多种细胞反应，包括M期进入、皮质细胞骨架重排、减数分裂纺锤体组装和性腺鞘细胞收缩。 这些反应是排卵、受精和减数分裂完成所必需的。 为了阐明细胞外信号促进卵母细胞成熟和排卵的机制，我们正在采取多管齐下的方法，通过研究MSP信号，候选受体和潜在的下游信号传导机制。 该提案旨在：1）确定向卵母细胞和鞘细胞发出信号的保守MSP结构域; 2）确定MSP是否与卵母细胞上的VAB-1（Eph）受体和SIM-2 HEM-2相关蛋白结合以促进成熟;以及3）对MSP信号传导途径进行遗传分析。

Oocyte maturation and ovulation are essential biological processes required for sexual reproduction. During oocyte maturation, oocytes enter meiotic M phase from prophase due to activation of the Cdc2/CyclinB protein kinase, maturation- promoting factor (MPF). In many species, hormones trigger signal transduction cascades that promote oocyte maturation and ovulation, but a major outstanding question concerns the detailed molecular mechanisms involved. A failure to correctly regulate this critical meiotic cell cycle transition can result in infertility, miscarriage, or Down's syndrome. The signal that promotes oocyte maturation in mammals is not known, and a receptor for a maturation-inducing substance has not been identified in any organism. To complement studies in vertebrates, we are using the nematode Caenorhaditis elegans as a model for studying the control of oocyte maturation and ovulation by intercellular signaling. Our studies demonstrate that a sperm cytoskeletal protein, the major sperm protein (MSP), is a bipartite signal that promotes oocyte maturation and gonadal sheath cell contraction in C. elegans. We have shown that MSP binds to oocytes and activates the conserved MAP kinase cascade. Our results indicate that MSP binding to oocytes requires the function of the VAB-1 Eph receptor tyrosine kinase and a highly conserved Hem family protein, SIM-2. MSP signaling results in diverse cellular responses including M-phase entry, cortical cytoskeletal rearrangement, meiotic spindle assembly, and gonadal sheath cell contraction. These responses are required for ovulation, fertilization, and completion of the meiotic divisions. To elucidate the mechanisms by which extracellular signals promote oocyte maturation and ovulation, we are taking a multipronged approach by studying the MSP signal, candidate receptors, and potential downstream signaling mechanisms. This proposal aims to: 1) define the conserved MSP domains that signal to oocytes and sheath cells; 2) determine whether MSP binds to the VAB-1 (Eph) receptor and the SIM-2 HEM-2-related protein on oocytes to promote maturation; and 3) conduct a genetic analysis of the MSP signaling pathway.