Recombination pathway and partner choice during C. elegans meiosis

染色体间的相互作用是产生遗传变异、维持基因组完整性的必要条件 通过修复双链DNA断裂（DSB），并确保染色体在 减数分裂，二倍体生物产生单倍体配子的专门细胞分裂程序， 精子和卵子重组事件中的扰动会损害这些基本的细胞功能， 最终导致癌症、生育问题或出生缺陷。减数分裂重组由DSB启动， 其利用有利于同源染色体利用的减数分裂特异性机制进行修复 （而不是姐妹染色单体）作为重组伴侣，并促进交叉（而不是姐妹染色单体） DSB修复（DSBR）过程的非交叉（noncrossover）结果。同源基因间的交叉重组 需要染色体来建立临时的物理连接， 减数分裂期间的分离。为了促进这些重组途径和合作伙伴的偏好 为了在同源染色体之间产生交叉，生殖细胞参与了一个专门的 DSBR程序在减数分裂前期的开始。在减数分裂前期晚期，减数分裂细胞经历一个 第二个开关在DSBR的要求，这是建议恢复到利用维修偏好典型 有丝分裂的细胞（例如，支持姐妹染色单体作为修复伴侣）。这一提议的转变 能够在减数分裂之前修复任何剩余的DSB，从而保持基因组的完整性。 利用C. elegans的实验系统，建议研究将如何解决不同的重组 在减数分裂过程中，使用了两条途径和配偶体， 并在减数分裂前修复任何剩余的DSB。为了评估时间和机械 这些途径和伙伴选择的特点，我将扩大我们最近发表的测定系统的范围 通过开发一种检测和区分DSB的不同修复产物的方法， 绝佳的价钱通过这个分析，我将直接测试减数分裂期间伴侣偏好的假设转换， 前期进展，并确定染色体位置对特定修复结果的影响， 伙伴的选择此外，利用各种遗传和细胞学技术，我将评估已知的作用， 减数分裂蛋白促进特定的减数分裂修复结果。此外，我将使用两种新试剂， 产生的评估动态的早期阶段的减数分裂DSBR活蠕虫，建立的作用，减数分裂 染色体结构在调控DSB形成和修复中的作用，并决定了特异性 修复伙伴的选择和早期DSBR阶段动态的类。总的来说，这些研究将揭示如何 重组途径和伴侣偏好确保染色体形成必要的连接， 染色体分离和修复DSB以维持基因组完整性。

Recombination between chromosomes is required to generate genetic variation, maintain genome integrity through the repair of double strand DNA breaks (DSBs), and ensure proper chromosome segregation during meiosis, the specialized cell division program by which diploid organisms generate haploid gametes such as sperm and eggs. Perturbations in recombination events can compromise these basic cellular functions, ultimately leading to cancer, fertility problems, or birth defects. Meiotic recombination is initiated by DSBs, which are repaired using meiosis-specific mechanisms that favor utilization of the homologous chromosome (instead of the sister chromatid) as the recombination partner and that promote a crossover (rather than noncrossover) outcome of the DSB repair (DSBR) process. Crossover recombination between homologous chromosomes is required to create temporary physical connections that promote proper chromosome segregation during meiosis. In order to promote these recombination pathway and partner preferences required for generating crossovers between homologous chromosomes, germ cells engage a specialized DSBR program at the onset of meiotic prophase. During late meiotic prophase, meiotic cells undergo a second switch in the DSBR requirements, which is proposed to revert to utilization of repair preferences typical of mitotically dividing cells (e.g. favoring the sister chromatid as the repair partner). This proposed switch would enable repair of any remaining DSBs prior to the meiotic divisions, thereby preserving genomic integrity. Utilizing the C. elegans experimental system, the proposed studies will address how different recombination pathways and partners are employed during meiosis to both promote crossover formation between homologs and repair any remaining DSBs prior to the meiotic divisions. To assess the temporal and mechanistic features of these pathway and partner choices, I will expand the scope of our recently published assay system by developing an assay to detect and distinguish the different repair products of DSBs induced at a defined site. With this assay, I will directly test for the hypothesized switch in partner preference during meiotic prophase progression and determine the effect of chromosomal position on specific repair outcomes and partner choices. Also, utilizing a variety of genetic and cytological techniques, I will assess the roles of known meiotic proteins in promoting specific meiotic repair outcomes. Further, I will utilize two new reagents I generated to assess dynamics of the early stages of meiotic DSBR in live worms, establish the roles of meiotic chromosome structures in regulating DSB formation and repair, and determine a relationship between specific repair partner choices and classes of early DSBR stage dynamics. Overall, these studies will reveal how recombination pathway and partner preferences ensure that chromosomes form the connections necessary for chromosome segregation and repair DSBs for maintaining genomic integrity.