Mechanisms of Recurrent, Parallel Loss of X/Y Pairing and Recombination at Meiosi

描述（由申请人提供）：我提出了一个培训计划，将为我在进化基因组学领域的独立研究生涯做准备。我获得了威斯康星大学麦迪逊分校遗传学实验室的博士学位，我的工作是哺乳动物物种在全球重组率差异的遗传和进化基础。然后，我在华盛顿大学基因组科学系完成了为期两年的博士后学习，在那里我获得了大量的经验和对大型基因组数据集的计算分析的熟练程度。通过提出的培训计划，我将扩展我的实验技能，包括基因组文库的构建，不同的细胞遗传学方法，以及哺乳动物模型系统中候选基因的功能分析。我提出了一个5年的研究计划，其中包括2年在北卡罗来纳州立大学（NCSU）的生物复杂性倡议中接受有组织的指导和培训，然后是3年作为独立调查员进行研究。拟议的培训计划将利用尖端的测序技术和染色体可视化的创新方法来阐明田鼠（Microtus属）的复发性变性和假常染色体区域（PAR）丢失的机制。这项研究将涉及多种研究领域，包括基因组学、进化生物学和细胞遗传学。特鲁迪·麦凯博士，威廉·尼尔·雷诺兹和杰出的大学遗传学教授，将作为我科学发展的主要导师。麦凯博士因其在进化和数量遗传学方面的工作而享誉世界，她培养的成功学生和博士后的记录令人印象深刻，这证明了她对培养年轻研究者的承诺和热情。NCSU遗传学系主任兼教授David Threadgill博士将在小鼠功能遗传学方面提供具体指导。来自NCSU的Matthew Breen博士和Lisa McGraw博士将分别在细胞遗传学和田鼠遗传学方面提供重点指导。教师研究兴趣的显著广度及其与拟议培训计划的智力和实验焦点的重叠使NCSU成为开展该研究指导阶段的最佳场所。哺乳动物的PAR促进异配子性染色体在减数分裂时的配对、突触和重组。这些过程对于正确的性染色体分离是不可或缺的。PAR中启动配对或重组失败可导致生精失败、不孕症和性染色体非整倍体，包括人类的特纳综合征和克莱因菲特综合征。尽管具有重要的减数分裂功能，但PAR在结构上是动态的、快速进化的，甚至在一些特殊的哺乳动物物种中已经完全消失。田鼠（Microtus属）在最近的PAR进化中显示出特别令人兴奋的趋势。在田鼠的系统发育中，有证据表明减数分裂时X/Y染色体配对有3个平行丢失，包括多个密切相关的物种对，有或没有减数分裂性染色体关联。我建议通过研究这些反复出现的进化事件来解决3个具体问题：在这些田鼠谱系中，是什么结构和序列水平的变化促成了PAR的退化和丧失？我建议在密切相关的田鼠物种之间进行细胞遗传学分析和基因组序列比较，有无减数分裂X/Y配对和重组来回答这个问题。2. 在减数分裂中不配对的、不交配的性染色体是如何可靠地分离的？我建议细胞学研究将性染色体动力学与减数分裂蛋白的定位模式联系起来，以确定候选的不匹配分离基因。3. 在田鼠中鉴定出的候选X/Y分离基因是否可以挽救具有PAR配对强制性要求的生物体的性染色体分离缺陷，这些生物体具有跨区域的破坏性突变？我将使用性染色体非整倍体频率高的小鼠模型进行这些功能测试。在田鼠的系统发育中，多个独立的PAR丧失事件的可用性呈现出一种逻辑过渡，即在专注于剖析一个物种的X/Y配对丧失基础的指导阶段，以及建立在这种训练基础上的独立研究者阶段，以确定其他田鼠物种的PAR降解和性染色体分离机制。该研究计划将为PAR进化和减数分裂时性染色体分离的机制提供关键见解，对理解人类性染色体非整倍体的发生具有潜在的临床意义。

DESCRIPTION (provided by applicant): I am proposing a training program that will prepare me for an independent research career in the field of evolutionary genomics. I received my PhD from the Laboratory of Genetics at the University of Wisconsin- Madison for my work on the genetic and evolutionary basis of mammalian species differences in global recombination rate. I then completed a 2-year postdoc in the Department of Genome Sciences at the University of Washington where I acquired considerable experience and proficiency in the computational analysis of large genomic datasets. Through the proposed training program, I will expand my experimental skill set to include genomic library construction, diverse cytogenetic methods, and functional analyses of candidate genes in mammalian model systems. I propose a 5-year research program composed of a 2-year phase of organized mentorship and training in the Initiative for Biological Complexity at North Carolina State University (NCSU), followed by a 3-year research phase as an independent investigator. The proposed training program will leverage cutting-edge sequencing technologies and innovative methods for chromosome visualization to elucidate the mechanisms of recurrent degeneration and loss of the pseudoautosomal region (PAR) in voles (genus Microtus). This research will draw on diverse research fields, including genomics, evolutionary biology, and cytogenetics. Dr. Trudy Mackay, William Neal Reynolds and Distinguished University Professor of Genetics, will act as the primary mentor for my scientific development. Dr. Mackay is a world-renowned for her work in evolutionary and quantitative genetics, and has an impressive record of successful students and postdocs as a testament to her commitment and enthusiasm for training young investigators. Dr. David Threadgill, Professor and head of the Department of Genetics at NCSU, will provide specific instruction in mouse functional genetics. Dr. Matthew Breen and Dr. Lisa McGraw, both at NCSU, will provide focused mentoring in cytogenetics and vole genetics, respectively. The remarkable breadth of faculty research interests and their overlap with the intellectual and experimental foci of the proposed training program make NCSU the optimal place for conducting the mentored phase of this research. The mammalian PAR promotes pairing, synapsis, and recombination between the heterogametic sex chromosomes at meiosis. These processes are integral to proper sex chromosome segregation. Failure to initiate pairing or recombination in the PAR can lead to spermatogenic failure, infertility, and sex chromosome aneuploidy, including Turner and Kleinfelter Syndromes in humans. Despite its important meiotic function, the PAR is structurally dynamic, rapidly evolving, and has even been completely lost in several exceptional mammalian species. Voles (genus Microtus) display particularly exciting trends in recent PAR evolution. Across the vole phylogeny, there is evidence for ¿3 parallel losses of X/Y chromosome pairing at meiosis, including multiple closely related species pairs with and without meiotic sex chromosome associations. I propose to study these recurrent evolutionary episodes to address 3 specific questions: 1. What structural and sequence-level changes precipitated the degeneration and loss of the PAR along these vole lineages? I propose cytogenetic assays and genome sequence comparisons between closely related vole species with and without meiotic X/Y pairing and recombination to answer this question. 2. How do unpaired, achiasmate sex chromosomes reliably segregate at meiosis? I propose cytological studies linking sex chromosome dynamics with the localization patterns of meiotic proteins to identify candidate achiasmate segregation genes. 3. Do candidate X/Y segregation genes identified in voles rescue sex chromosome segregation defects in organisms with obligate requirements for PAR pairing that harbor disruptive mutations across the region? I will carry out these functional tests using a mouse model with a high frequency of sex chromosome aneuploidy. The availability of multiple, independent episodes of PAR loss across the vole phylogeny presents a logical transition between a mentored phase focused on dissecting the basis of X/Y pairing loss in one species set, and an independent investigator phase that builds on this training to determine the mechanisms of PAR degradation and sex chromosome segregation in other vole species. The proposed research program will provide key insights into the mechanisms of PAR evolution and sex chromosome segregation at meiosis, with potential clinical consequences for understanding the genesis of sex chromosome aneuploidies in humans.