Recombination pathway and partner choice during C. elegans meiosis

染色体之间的重组是产生遗传变异、维持基因组完整性所必需的 通过修复双链DNA断裂(DSB)，并确保在 减数分裂，二倍体生物产生单倍体配子的特殊细胞分裂程序，如 精子和卵子。重组事件中的扰动会损害这些基本细胞功能， 最终导致癌症、生育问题或出生缺陷。减数分裂重组是由DSB启动的， 它们是用减数分裂特有的机制修复的，这种机制有利于同源染色体的利用 (而不是姐妹染色单体)作为重组伙伴，促进交叉(而不是 非交叉)DSB修复(DSBR)过程的结果。同源基因间的交叉重组 染色体需要创建临时的物理连接，以促进正确的染色体 减数分裂过程中的分离。为了促进这些重组途径和伙伴偏好 在同源染色体之间产生交叉所需的生殖细胞进行专门的 减数分裂前期的DSBR程序。在减数分裂后期的前期，减数分裂细胞经历 DSBR要求中的第二个开关，建议恢复到使用典型的维修首选项 有丝分裂的细胞(例如，倾向于姐妹染色单体作为修复伙伴)。此建议的交换机 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。 利用线虫的实验系统，拟议的研究将解决如何不同的重组 在减数分裂过程中，途径和伙伴都被用来促进同系物之间的交叉形成 并在减数分裂之前修复任何剩余的DSB。评估时代性和机械性 关于这些途径的特征和伙伴选择，我将扩大我们最近发布的检测系统的范围 通过建立一种检测和区分在定义的 地点。有了这个测试，我将直接测试减数分裂过程中伴侣偏好的假设开关。 早期进展并确定染色体位置对特定修复结果的影响 合作伙伴选择。此外，利用各种遗传学和细胞学技术，我将评估已知的 减数分裂蛋白促进特定的减数分裂修复结果。此外，我将使用两种新的试剂I 生成以评估活虫减数分裂早期阶段DSBR的动力学，建立减数分裂的作用 染色体结构在调节DSB的形成和修复中，并确定特定的关系 修复早期DSBR阶段动态的合作伙伴选择和类别。总体而言，这些研究将揭示 重组途径和伴侣偏好确保染色体形成必要的连接 染色体分离和修复双链断裂以保持基因组的完整性。

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.