Genetic and Molecular Analysis of Oocyte Meiotic Prophase Arrest in C. elegans

9506220 Schedl 减数分裂 I 前期细胞周期的停滞是基本上所有多细胞动物卵子发生的保守特征。 从海星到人类，生物体中的卵母细胞通过一种尚不清楚的机制维持这种停滞状态直到排卵。 该提案引入了一种用于分离和表征减数分裂前期细胞周期停滞的分子调节因子的遗传策略。最近对线虫秀丽隐杆线虫进行的遗传筛选已鉴定出突变体，其中卵母细胞停滞在 MI 前期的终动期无法维持。在 oar-1 和 oar-2 突变体（oar = 卵母细胞减数分裂前期停滞缺陷）中，卵母细胞脱离停滞状态并进行内有丝分裂复制其 DNA。 已经制定了策略来区分 Oar 突变体和产生内有丝分裂卵母细胞的其他突变体。重要的是，我们已经获得了与 Oar 具有相反表型的突变体； olk-1（olk=卵母细胞阻滞锁）卵母细胞在阻滞通常丢失的情况下保持阻滞。由 oar 和 olk 基因定义的维持减数分裂停滞的途径很可能涉及从体细胞到卵母细胞的细胞通讯。 oar-1 的分析与细胞信号需要维持减数分裂停滞的结论一致；克隆显示 oal-1 编码其他系统中已知的 Sec61p γ 蛋白，以促进蛋白质易位到 ER 中，马赛克分析显示，种系中特别需要 oar-1 活性，以防止卵母细胞停滞的损失。因此，Oar-1 可能会将跨膜受体转移到卵母细胞表面，以接收逮捕信号。该提案将启动对维持线虫卵母细胞减数分裂前期停滞的途径进行更广泛的遗传和分子研究。 Schedl 博士将：1) 使用遗传筛选鉴定卵母细胞减数分裂前期停滞所需的基因，2) 对桨收集中的突变体进行遗传学和表型表征，以及 3) 对停滞“loc-1”突变体 olk-1 进行遗传学表征。 ***

9506220 Schedl Arrest of the cell cycle in prophase of meiosis I is a conserved feature of oogenesis in essentially all multicellular animals. Oocytes in organisms from starfish to humans maintain this arrested state until ovulation by a mechanisms that is not well understood. This proposal introduces a genetic strategy for isolating and characterizing molecular regulators of meiotic prophase cell cycle arrest. Recent genetic screens performed in the nematode Caenorhabditis elegans have identified mutants where oocyte arrest in diakinesis of MI prophase fails to be maintained. In oar-1 and oar-2 mutants (oar= oocyte meiotic prophase arrest defective), oocytes leave arrest and endomitotically replicate their DNA. Strategies have been developed to distinguish Oar mutants from other mutants producing endomitotic oocytes. Importantly, a mutant has been obtained with a phenotype opposite to Oar; olk-1 (olk= oocyte arrest lock) oocytes maintain arrest under conditions when arrest is usually lost. It is likely that the pathway for maintenance of meiotic arrest defined by the oar and olk genes involves cell cell communication from the soma to the oocyte. Analysis of oar-1 is consistent with the conclusion that a cell cell signal is needed to maintain meiotic arrest; cloning reveals that oal-1 encodes a Sec61p gamma protein known in other systems to facilitate protein translocation into the ER, and mosaic analysis shows oar-1 activity is needed specifically in the germline to prevent loss of oocyte arrest. Oar-1 may therefore act to translocate a transmembrane receptor to the oocyte surface for reception of the arrest signal. This proposal will initiate a more extensive genetic and molecular investigation of the pathway maintaining oocyte meiotic prophase arrest in C. elegans. Dr. Schedl will:1) Identify genes necessary for oocyte meiotic prophase arrest using a genetic screen, 2) Genetically and phenotypically characterize mutants in the oar collection, and 3) Genet ically characterize the arrest "loc-1" mutant, olk-1. ***