Role of Spo11 and recombination in mouse meiosis

描述(申请人提供)：我们的目标是了解哺乳动物减数分裂重组和监测它的检查点。重组产生同源染色体之间的物理连接，这对准确的分离是必不可少的。如果重组改变，染色体分离就会受到影响，从而导致配子非整倍体。重组的分子机制和防止重组错误的过程还没有被很好地理解。小鼠是这些研究的理想之选，因为它与人类的相关分子过程广泛保守。具体目的是：1.研究小鼠交叉内环境的稳定性。在酵母中，即使在DSB频率降低的情况下，交换数量也保持不变(“交换稳态”)。同样的过程也可以在老鼠身上进行。这一假设将通过细胞学和分子分析对雄性和雌性动物的重组进行验证，并减少Spo11的剂量。Spo11是一种编码启动重组的蛋白质的基因。2.明确ATM在减数分裂重组中的作用。检查点激酶ATM是修复减数分裂DNA断裂和交叉控制所必需的。在缺乏ATM的小鼠中，重组蛋白的行为和重组产物的结构将被确定。3.定义Spo11剪接异构体的功能。已经描述了小鼠和人Spo11的多种剪接变体。编码蛋白的功能尚不清楚。这个问题将通过鉴定携带转基因或表达个别亚型的靶向突变的小鼠来解决。4.确定TRIP13(PCH2)在监测染色体突触缺陷中的作用。最近对酵母和线虫的研究表明，染色体突触检查点的存在有别于重组检查点。我们将测试突触检查点蛋白PCH2的小鼠同源物是否在哺乳动物减数分裂中以类似的途径发挥功能。相关性：卵子或精子中的染色体数目异常会导致发育障碍或自然流产。这些异常通常是由于减数分裂同源重组中的缺陷导致的染色体分离不当所致。这个项目将解决哺乳动物如何控制减数分裂重组以及在出现问题时做出反应的基本问题。

DESCRIPTION (provided by applicant): Our goal is to understand both mammalian meiotic recombination and the checkpoints that monitor it. Recombination generates physical connections between homologous chromosomes that are essential for accurate segregation. If recombination is altered, chromosome segregation is affected, and gamete aneuploidy results. The molecular mechanisms of recombination and the processes that protect against recombination errors are not well understood. Mouse is ideal for these studies because of extensive conservation of relevant molecular processes with humans. Specific aims are to: 1. Characterize crossover homeostasis in mouse. In yeast, crossover numbers are maintained even when DSB frequencies are decreased ("crossover homeostasis"). The same process may operate in mouse. This hypothesis will be tested by cytological and molecular analysis of recombination in male and female animals with reduced dosage of Spo11, the gene encoding the protein that initiates recombination. 2. Define the roles of ATM in meiotic recombination. The checkpoint kinase ATM is required for repair of meiotic DMA breaks and for crossover control. Behaviors of recombination proteins and structures of recombination products will be determined in mice lacking ATM. 3. Define the functions of Spo11 splicing isoforms. Multiple splice variants of mouse and human Spo11 have been described. The functions of the encoded proteins are not known. This issue will be addressed through characterization of mice carrying transgenes or targeted mutations that express individual isoforms. 4. To determine the role of TRIP13 (PCH2) in monitoring chromosome synapsis defects. Recent studies in yeast and nematode demonstrated the existence of a chromosome synapsis checkpoint that is distinct from the recombination checkpoint. We will test whether a mouse homolog of the synapsis checkpoint protein PCH2 functions in a similar pathway in mammalian meiosis. Relevance: Abnormal chromosome numbers in eggs or sperm cause developmental disabilities or spontaneous abortion. These abnormalities often arise because of improper separation of chromosomes caused by defects in meiotic homologous recombination. This project will address fundamental questions about how mammals control meiotic recombination and respond when there are problems.