Molecular Mechanisms of Genetic Recombination in Mammals

项目总结/摘要 非整倍体--个体中染色体数目错误--是导致出生的主要原因 人类的缺陷它是由于同源染色体（同系物）分离错误引起的 在配子形成过程中。通过减数分裂重组确保适当的分离。它始于 引入DNA双链断裂（DSB），然后使用完整的DNA进行修复 同源染色体作为模板。这导致同源物的时间关联 通过交换（CO）稳定。这种成对的安排确保了 同源染色体与分裂细胞核的两极相连， 每对一个同源物。不能配对的同源物随机分离，并且具有50%的 有机会进入同一个子细胞。沿着CO的缺乏，CO的位置效应 放置也导致非整倍性。重组事件的空间分布被控制在 不同的层次和定义这种调节的机制是必要的，以了解为什么一些 这些事件都逃脱了这种控制。我们的长期目标是阐明缺陷背后的机制 减数分裂重组导致哺乳动物的非整倍性。在这项研究中，我们将采取全基因组 的方法来定义CO在小鼠中的放置机制。(i)通过细胞学评价， 小鼠减数分裂染色体，我们将确定减数分裂DSB的位置是随机的还是 显示干扰，即一个DSB的形成抑制了第二个DSB的形成， 相邻区域。这将有助于澄清CO干扰的实施机制。 (ii)使用染色质免疫沉淀，然后直接高通量测序，我们将映射 小鼠基因组中倾向于发生减数分裂DSB的区域（减数分裂DSB的热点）。 突变并不是均匀分布在整个基因组中， 与重组热点相关的基因将为它们背后的机制提供线索。 阵(iii)我们将使用类似的方法绘制减数分裂CO的热点。比较 分析这两张图将有助于阐明导致CO形成的途径， 参与CO/NCO指定的机制。总的来说，我们的研究结果将阐明 参与CO放置的机制的几个重要方面，也将创造新的 为今后研究揭示减数分裂重组控制机制提供了途径。突变 减少或消除重组总是与减数分裂停滞或染色体 分离错误导致不育或非整倍性。理解推动重组的力量 在制定预防措施和治疗方法之前是必要的。

PROJECT SUMMARY/ABSTRACT Aneuploidy - the wrong number of chromosomes in an individual - is the leading cause of birth defects in humans. It results from errors in the segregation of homologous chromosomes (homologs) during gametogenesis. The proper segregation is ensured by meiotic recombination. It begins with the introduction of DNA double stranded breaks (DSBs) followed by their repair using the intact DNA of a homologous chromosome as a template. This leads to a temporal association of the homologs stabilized by crossing-overs (COs). Such an arrangement into pairs ensures orderly segregation of the homologous chromosomes to the opposite poles of dividing nuclei so that each gamete receives one homolog of each pair. The homologs that fail to pair segregate randomly, and have a 50% chance to go into the same daughter cell. Along with the lack of COs, positional effects of CO placement also contribute to aneuploidy. Spatial distribution of recombination events is controlled at different levels and defining the mechanisms of this regulation is necessary to understand why some of the events escape this control. Our long-term goal is to elucidate the mechanisms behind faulty meiotic recombination resulting in aneuploidy in mammals. In this study we will take a genome-wide approach to define the mechanisms of CO placement in the mouse. (i) By cytological evaluation of the mouse meiotic chromosomes we will determine whether placement of meiotic DSBs is random or displays interference, i.e. the formation of one DSB suppresses the formation of a second one in adjacent regions. This will help to clarify the mechanisms involved in imposition of CO interference. (ii) Using chromatin immunoprecipitation followed by direct high-throughput sequencing we will map the regions of mouse genome where meiotic DSBs tend to occur (hotspots of meiotic DSBs). Recombination is not evenly distributed throughout the genome and defining the particular features associated with recombination hotspots will provide the cues to the mechanism behind their formation. (iii) We will map the hotspots of meiotic COs using the similar approach. Comparative analysis of these two maps will help to elucidate the pathways leading to CO formation, and the mechanisms involved in CO/NCO designation. Overall, the results from our studies will illuminate several important aspects of the mechanisms involved in CO placement, and will also create new avenues for future research in delineating the mechanism of meiotic recombination control. Mutations that reduce or abolish recombination are invariably associated with meiotic arrest or chromosome segregation errors leading to infertility or aneuploidy. Understanding the forces driving recombination is necessary before preventive measures and therapeutic approaches can be developed.