Mechanisms and regulation of meiotic recombination"

项目总结/摘要 减数分裂是一个严格调控的过程，确保形成单倍体配子。未能隔离 减数分裂期间的同源染色体导致非整倍体，导致染色体疾病 比如唐氏综合症和流产同源不分离的发生率随着卵母细胞的增加而增加 年龄年龄相关的不分离的一个假设原因是老化的卵母细胞不能维持交叉， 同源物之间的物理联系，直到它们排卵。交叉是通过交叉形成的， 通过同源修复双链DNA断裂形成的同源物之间的交换 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。 这种现象被称为“交叉模式”。理解交叉形成的规律 和模式化，因此同源重组机制，是不可或缺的打击年龄相关的 不孕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），其中链来自不同亲本染色体的DNA。经典的减数分裂HR模型 表明交叉是通过双霍利迪结（dHJ）形成的，这种结构中两个DNA分子 是通过在两个相邻位点交叉连接的。在这个经典模型中，连接的dHJ产生 所有的交叉都是以两种模式之一被切割，产生两种可能的hDNA特征。模型 预测这两种模式的可能性相等，但只有一个hDNA签名已被观察到。这 hDNA标签偏好性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 重组的测试基因座在果蝇，但重新定义减数分裂重组模型 需要比这种方法更广泛的hDNA分析。为了克服这个 障碍，我将开创“hetSeq”，一种全基因组测序技术，用于检测减数分裂中的hDNA 产品，继续重新定义这个模型。我们对交叉监管的理解还有一个差距， 虽然交叉模式自20世纪初以来就已被观察到，但它与同源 重组机制尚不清楚。许多减数分裂蛋白在同源染色体中具有已知的功能。 复合，并且它们的耗尽导致交叉图案化缺陷。我正在开发一个数学 重组模型来测试关于这些蛋白质的假设。为了做到这一点，我将改变交叉方面 在模型中形成模式，并将输出与先前从突变体获得的实验数据进行比较 缺乏这些蛋白质。我还使用这个模型来开发一个模拟重组使用整个- 基因组测序数据。这些实验将加深对交叉的理解 该法规旨在为防治年龄相关性不育和非整倍体提供指导。

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.