Mechanisms and regulation of meiotic recombination"

项目摘要/摘要 减数分裂是确保单倍体配子形成的一个严格调控的过程。没有实行隔离 减数分裂过程中的同源染色体导致非整倍体，导致染色体紊乱。 比如唐氏综合症和流产。同源不分离的发生率随卵母细胞的增加而增加 年龄。与年龄相关的不分离的一个假设原因是老化的卵母细胞无法维持交叉， 同系物之间的物理联系，直到它们被排卵。交叉是通过交叉形成的，遗传的 通过同源基因修复双链DNA断裂形成的同源基因之间的交换 重组。为了确保适当的同源分离，交叉的数量和空间模式是紧密的 这是一种被称为“交叉图案化”的现象。理解交叉形成的规律 和图案化，因此同源重组机制，是对抗年龄相关的不可或缺的 不孕不育。同源重组中的途径选择可通过异源双链DNA在产物中追踪 (HDNA)，DNA中的链来自不同的亲本染色体。经典的减数分裂HR模型 表明交叉是通过双Holliday结(DHJ)形成的，在这种结构中，两个DNA分子 在相邻的两个位置通过其链的交叉连接。在这个经典的模型中，结扎的dHJ产生了 所有的交叉都被切割成两种模式之一，产生两个可能的hDNA签名。模型 预测这两种模式的可能性相同，但只观察到其中一种hDNA签名。这 HDNA特征偏向要求对减数分裂重组模型进行修正。我们的实验室已经绘制了hDNA图谱 果蝇测试基因座的重组，但重新定义减数分裂重组模型 与这种方法相比，需要对hDNA进行更广泛的分析。要克服这一点 障碍，我将开创hetSeq的先河，这是一种从减数分裂中检测hDNA的全基因组测序技术 产品，继续重新定义这一模式。在我们对交叉监管的理解中，还有一个差距是 虽然从20世纪初就观察到了交叉图案，但它与同源 重组机制尚不清楚。许多减数分裂蛋白在同源植物中具有已知的功能 复合以及它们的耗尽导致交叉图案化缺陷。我正在开发一种数学方法 重组模型来检验关于这些蛋白质的假说。为了做到这一点，我将改变交叉的各个方面 在模型中构图，并将输出与之前从突变体获得的实验数据进行比较 缺乏这些蛋白质。此外，我还使用这个模型来开发一个重组的模拟，它使用了整个- 基因组测序数据。拟议中的实验将加强对交叉的理解 条例，以提供指导，以对抗年龄相关性不孕和非整倍体。

Project Summary/Abstract Meiosis is a tightly regulated process that ensures formation of haploid gametes. Failure to segregate homologous chromosomes during meiosis results in aneuploidy, leading to chromosomal disorders such as Down syndrome and miscarriage. Incidences of homolog nondisjunction increase with oocyte age. A hypothesized cause of age-related nondisjunction is that aging oocytes are unable to maintain chiasmata, physical linkages between homologs, until they are ovulated. Chiasmata are formed via crossovers, genetic exchanges between homologs that are formed by repairing double-strand DNA breaks via homologous recombination. To ensure proper homolog segregation, the number and spatial patterning of crossovers is tightly regulated in a phenomenon known as “crossover patterning.” Understanding regulation of crossover formation and patterning, and therefore homologous recombination mechanism, is integral to combatting age-related infertility. Pathway choices within homologous recombination are traceable in products via heteroduplex DNA (hDNA), DNA in which the strands come from different parental chromosomes. The classic meiotic HR model indicates that a crossover is formed via a double Holliday junction (dHJ), a structure in which two DNA molecules are linked via criss-crossing of their strands at two adjacent sites. In this classic model, ligated dHJs give rise to all crossovers by being cleaved in one of two patterns, generating two possible hDNA signatures. The model predicts that both patterns are equally likely, yet only one of the hDNA signatures has been observed. This hDNA signature bias demands revision of the meiotic recombination model. Our lab has mapped hDNA at recombinants of a test locus in Drosophila melanogaster, but redefining the meiotic recombination model requires much more extensive analysis of hDNA than is possible with this methodology. To overcome this obstacle, I will pioneer “hetSeq”, a whole-genome sequencing technique to detect hDNA from meiotic products, to continue redefining this model. A further gap in our understanding of crossover regulation is that although crossover patterning has been observed since the early 1900s, its relationship to homologous recombination mechanism remains unclear. Many meiotic proteins have a known function in homologous recombination, and their depletion leads to crossover patterning defects. I am developing a mathematical model of recombination to test hypotheses about these proteins. To do this, I will alter aspects of crossover patterning within the model and compare the output to previously obtained experimental data from mutants lacking these proteins. I am additionally using this model to develop a simulation of recombination using whole- genome sequencing data. The proposed experiments will strengthen understanding of crossover regulation to provide guidance in combatting age-related infertility and aneuploidy.