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

小行星9506220 减数分裂I前期细胞周期的停滞是卵子发生的一个保守特征，基本上存在于所有的多细胞动物中。 从海星到人类的生物体中的卵母细胞保持这种停滞状态，直到排卵，其机制尚不清楚。 该建议介绍了一种遗传策略，用于分离和表征减数分裂前期细胞周期阻滞的分子调节剂。最近在线虫线虫中进行的遗传筛选已经确定了突变体，其中在MI前期终变期中卵母细胞阻滞不能维持。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，卵母细胞离开停滞并在有丝分裂中复制它们的DNA。 已经开发了策略来区分Oar突变体与产生内有丝分裂卵母细胞的其他突变体。重要的是，突变体已获得与Oar相反的表型; olk-1（olk=卵母细胞阻滞锁）卵母细胞在阻滞通常丢失的条件下保持阻滞。由oar和olk基因定义的维持减数分裂停滞的途径可能涉及从索马到卵母细胞的细胞通讯。 oar-1的分析与维持减数分裂停滞需要细胞信号的结论一致;克隆揭示oal-1编码在其他系统中已知的Sec 61 p γ蛋白，以促进蛋白质易位到ER中，并且嵌合体分析显示oar-1活性在种系中特别需要，以防止卵母细胞停滞的丧失。因此，Oar-1可以将跨膜受体转移到卵母细胞表面，以接收停滞信号。这一建议将启动一个更广泛的遗传和分子研究的途径维持卵母细胞减数分裂前期停滞在C。优雅Schedl博士将：1）使用遗传筛选鉴定卵母细胞减数分裂前期阻滞所需的基因，2）遗传和表型表征桨收集中的突变体，3）遗传表征阻滞“loc-1”突变体，olk-1。 ***

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. ***