Genetic Recombination in C.elegans

描述（由申请人提供）：我们的长期目标是了解基因重组如何有助于染色体的忠实遗传。基因重组对于有性生殖的生物体是至关重要的，因为同源染色体的DNA分子之间的交叉重组事件以及由此产生的交叉，是减数分裂I分裂时染色体分离的必要条件。不能形成交叉会导致染色体错误分离和随之而来的非整倍体，这是人类流产和出生缺陷的主要原因之一。减数分裂交叉是通过有意诱导双链DNA断裂（dsb）来完成的，然后在减数分裂特异性染色体结构的背景下，使用减数分裂特异性DSBR途径的修饰来修复这些断裂。这一过程受到多个层面的调控，以确保dsb在适当的时间背景下形成和修复，既避免对基因组完整性构成威胁，又保证每对染色体将经历促进同源分离所需的必要交叉。我们正在研究秀丽隐杆线虫（一种简单的后生动物，特别适合在单一实验系统中结合复杂的细胞学和遗传学方法）中调节和执行减数分裂交叉和交叉形成的机制，并且在其中已显示出强大的交叉调节机制。提出的工作将利用最近的进展，允许1)交叉触发的染色体状态变化和DSBR模式变化的细胞学可视化，以及2)操纵减数分裂前期进程的时间和DSB形成的时间和位置。我们将研究染色质相关蛋白HIM-17在促进减数分裂重组起始、染色质修饰和减数分裂进入调控中的作用机制。我们将研究减数分裂重组的机制和调控，使用设计的方法来操纵DSB形成的时间和位置以及减数分裂前期进程的时间。我们将使用大量的细胞学和遗传功能分析来研究交叉重组机制中新发现的成分的作用。最后，我们将探讨HIM- 6/BLM在功能性交叉形成中的作用。除了阐明减数分裂过程中染色体遗传的重要机制外，后者的目的应该对布卢姆综合征（一种导致所有类型癌症易感性的遗传性疾病）患者基因组不稳定的病因有深入的了解。公共卫生相关性：拟议的研究将增加我们对维持染色体完整性和确保染色体忠实遗传的机制的理解。这项工作与人类健康高度相关，因为染色体遗传错误是流产和出生缺陷的主要原因之一，也是导致癌症发生和发展的一个主要因素。该研究计划的一个组成部分将阐明导致布卢姆综合征患者染色体不稳定的机制。布卢姆综合征是一种遗传性疾病，易患所有类型的癌症。

DESCRIPTION (provided by applicant): Our long term goal is to understand how genetic recombination contributes to the faithful inheritance of chromosomes. Genetic recombination is of central importance to sexually reproducing organisms, since crossover recombination events between the DNA molecules of homologous chromosomes, and the resulting chiasmata, are necessary for proper chromosome segregation at the meiosis I division. Failure to form crossovers leads to chromosome missegregation and consequent aneuploidy, one of the leading causes of miscarriages and birth defects in humans. Meiotic crossing over is accomplished by deliberate induction of double-strand DNA breaks (DSBs), followed by repair of these breaks using meiosis-specific modifications of DSBR pathways in the context of meiosis-specific chromosome architecture. This process is subject to multiple levels of regulation to ensure that DSBs are formed and repaired in an appropriate temporal context, both to avoid posing a threat to genome integrity and to guarantee that each chromosome pair will undergo the obligate crossover required to promote homolog segregation. We are investigating the mechanisms that regulate and execute meiotic crossing over and chiasma formation in the nematode C. elegans, a simple metazoan organism that is especially amenable to combining sophisticated cytological and genetic approaches in a single experimental system, and in which robust crossover regulation mechanisms have been shown to operate. The proposed work will exploit recent advances that allow 1) cytological visualization of crossover-triggered changes in chromosome state and changes in the mode of DSBR, and 2) manipulation of the timing of meiotic prophase progression and the timing and location of DSB formation. We will investigate the mechanisms by which chromatin-associated protein HIM-17 functions in promoting initiation of meiotic recombination, chromatin modification and regulation of meiotic entry. We will investigate the mechanisms and regulation of meiotic recombination using methods designed to manipulate the timing and location of DSB formation and the timing of meiotic prophase progression. We will use a large battery of cytological and genetic functional assays to investigate the roles of newly-identified components of the crossover recombination machinery. Finally, we will investigate the role of HIM- 6/BLM in the formation of functional chiasmata. In addition to elucidating mechanisms important for chromosome inheritance during meiosis, this latter aim should yield insights regarding the etiology of genomic instability in patients with Bloom Syndrome, an inherited disorder causing predisposition to all types of cancer. PUBLIC HEALTH RELEVANCE: The proposed research will increase our understanding of the mechanisms that maintain chromosome integrity and ensure faithful inheritance of chromosomes. The work is highly relevant to human health, as errors in chromosome inheritance are one of the leading causes of miscarriages and birth defects and are also a major factor contributing to the development and progression of cancer. One component of the research plan will shed light on the mechanisms that lead to chromosome instability in patients with Bloom Syndrome, an inherited disorder causing predisposition to all types of cancer.