Preventing Age-Associated Oocyte Aneuploidy: Mechanisms Behind the Drosophila melanogaster Centromere Effect

项目概要/摘要 在减数分裂过程中，同源物之间的交换促进了染色体的精确分离， 非整倍体，从而防止流产和染色体疾病，如唐氏综合症。的 减数分裂交换的调节和放置是防止年龄相关减数分裂的重要保障。 缺陷和不孕症，因为不分离（NDJ）的风险随着母亲年龄的增加而增加。 当程序性双链断裂（DSB）通过DNA修复时，形成减数分裂交换（CO）。 同源重组然而，只有一部分DSB被修复以形成CO;其余的被修复为 非交叉（NCO）。尽管减数分裂DSB分布在整个染色体上，但CO的位置是 受到三种模式现象的复杂调控。其中之一，着丝粒效应（CE），确保 近着丝粒区的CO被排除，这对减数分裂细胞作为近着丝粒区至关重要。 CO会增加NDJ的风险。此外，增加母亲年龄已被证明会削弱CE， 这可能解释了为什么老年女性NDJ发病率增加。虽然首次在果蝇中观察到 在1932年，行政长官背后的机制至今仍不为人知。这里提出的实验旨在 解决关于防止错误分离事件的重要细胞过程的知识方面的这一差距， 尤其是高龄产妇。最近，我们的实验室表明，行政长官是不同的 在果蝇近着丝粒处发现的两类异染色质中建立。在高度重复的 α异染色质紧邻着丝粒，观察到CO的完全排除，而 邻近近端常染色质的较少重复的β异染色质显示出距离依赖性CO 镇压在此基础上，我将进一步探讨行政长官的产生机制 在这两类臂间异染色质中。关于CE机制的一个突出问题 围绕着着丝粒周围的异染色质和着丝粒本身对CE的贡献。为数不多 在过去的世纪中，研究中心间交叉的研究试图建立一个 在果蝇中比另一个更重要，但未能达成共识。因此，臂间异染色质 被认为是从相邻间隔中减少CO的积极参与者到其他任何事情 而不是常染色质和着丝粒之间的被动间隔区。通过本文中概述的实验， 建议，我会问如何着丝粒间异染色质和着丝粒有助于CE 彼此独立地，特别关注高度重复的α异染色质。 研究α异染色质的作用，将其与臂间异染色质作为一个整体分开 在表现CE是一个新的研究领域内的更广泛的问题，CE是如何建立的。在 总之，这一建议将增加我们对防止年龄增长的机制的理解- 相关的非整倍体和不育通过揭示减数分裂交叉模式。

Project Summary/Abstract During meiosis, crossing-over between homologs facilitates accurate chromosome segregation and prevents aneuploidy, which in turn forestalls miscarriages and chromosomal disorders such as Down syndrome. The regulation and placement of meiotic crossovers acts as a vital safeguard against age-associated meiotic defects and infertility, as the risk of non-disjunction (NDJ) increases with increasing maternal age. Meiotic crossovers (COs) are formed when programmed double-strand breaks (DSBs) are repaired through homologous recombination. However, only a subset of DSBs are repaired to form COs; the rest are repaired as non-crossovers (NCOs). Despite meiotic DSBs being distributed throughout the chromosome, CO placement is intricately regulated by three types of patterning phenomena. One of these, the centromere effect (CE), ensures the exclusion of COs in centromere-proximal regions and is crucial to the meiotic cell as centromere-proximal COs increase the risk of NDJ. Furthermore, increasing maternal age has been shown to weaken the CE, potentially explaining why NDJ incidence increases in older women. Although first observed in Drosophila in 1932, the mechanisms behind the CE remain unknown even today. The experiments proposed here aim to address this gap in knowledge regarding a vital cellular process that prevents mis-segregation events, especially in those with advanced maternal age. Recently, our lab showed that the CE is differentially established in the two classes of heterochromatin found at the Drosophila pericentromere. In the highly repetitive alpha heterochromatin immediately adjacent to the centromere, a complete exclusion of COs is observed, while the less repetitive beta heterochromatin adjacent to proximal euchromatin shows a distance dependent CO suppression. I will build on these results by investigating the mechanisms of how the CE is established in these two classes of pericentric heterochromatin. A prominent question regarding CE mechanisms centers around how pericentromeric heterochromatin and the centromere itself contribute to the CE. The few studies that have addressed pericentric crossing-over in the past century have attempted to establish one as more important than the other in Drosophila but failed to arrive at a consensus. Thus, pericentric heterochromatin has been considered everything from an active participant in CO reduction in adjacent intervals to nothing more than a passive spacer between euchromatin and the centromere. Through the experiments outlined in this proposal, I will ask how pericentric heterochromatin and the centromere contribute to the CE independently of each other, particularly focusing on highly repetitive alpha heterochromatin. Investigating the role of alpha heterochromatin as separate from that of pericentric heterochromatin as a whole in manifesting the CE is a novel area of research within the broader question of how the CE is established. In summary, this proposal will increase our understanding of the mechanisms that safeguard against age- related aneuploidy and infertility through shedding light on meiotic crossover patterning.