CAREER: Engineering genome topology to attenuate pathologic short tandem repeat instability

DNA序列存储信息，对这些信息的访问在许多层面上受到控制。分散在DNA中的是随机重复序列，称为短串联重复序列（STRs）。STRs有助于调节基因表达，也可以在长度上扩张和收缩。STR的过度扩张可导致许多疾病，包括肌萎缩性侧索硬化症（Lou Gehrig 's disease）、阿尔茨海默氏症和亨廷顿舞蹈症。该项目将重点研究导致STR扩展并导致疾病的原因。正确应用统计和计算工具是在这方面取得进展的关键。培训项目将为学生提供学习这些技术的机会。关于转录因子和表观遗传标记如何在线性基因组的背景下调节大脑中的神经突触，我们已经知道了很多。然而，我们对脆性X染色体综合征（FXS）、亨廷顿氏病和阿尔茨海默病等神经系统疾病中突触严重破坏的机制的理解仍然存在严重的局限性。最近，Cremins实验室发现，几乎所有与疾病相关的STRs （daSTRs）都位于称为拓扑相关结构域（TAD）的基因组折叠模式的边界。实验室继续发现TAD边界在FXS中被严重破坏，从而揭示了基因序列的高阶折叠作为理解具有突触缺陷的神经系统疾病的新维度。一个尚未解决的根本问题是，为什么一些str容易受到病理性扩增的影响，而人类基因组中成千上万的重复序列却相对稳定。该项目的总体目标是了解建筑蛋白CTCF的占用与TAD边界STR不稳定性之间的机制联系。我们的中心假设是，具有超高CTCF密度的TAD边界代表人类基因组中易受不稳定影响的热点。为了验证这一假设，我们提出了实验和计算研究：(1)定量测量CTCF密度和双链断裂对STR不稳定性的作用；(2)设计CTCF占用以诱导STR扩展的功能变化。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

DNA sequences store information, and access to this information is controlled at many levels. Scattered across DNA are random, repeated sequences referred to as short tandem repeats (STRs). STRs help regulate gene expression and can also expand and contract in length. Overexpansion of STR's can lead to a number of diseases, including ALS (Lou Gehrig’s disease), Alzheimer’s, and Huntington’s. This project will focus on what causes STR expansion that leads to disease. The proper application of statistics and computational tools are key to making progress in this effort. A training program will provide students with the opportunity to learn those techniques.Much is already known regarding how transcription factors and epigenetic marks work in the context of the linear genome to regulate neural synapses in the brain. Yet, severe limitations still exist in our ability to understand the mechanisms by which synapses are severely disrupted in neurological disorders such as fragile X syndrome (FXS), Huntington’s disease, and Alzheimer’s disease. Recently, the Cremins lab discovered that nearly all disease-associated STRs (daSTRs) are located at boundaries demarcating a genome folding pattern termed the topologically associating domain (TAD). The lab went on to discover that TAD boundaries are severely disrupted in FXS, thus revealing higher-order folding of the genetic sequence as a new dimension in understanding neurological disorders with synaptic defects. A fundamental unresolved question is why some STRs are susceptible to pathologic expansion, whereas hundreds of thousands of repeat tracts across the human genome are relatively stable. The overall objective of this project is to understand the mechanistic link between occupancy of the architectural protein CTCF and STR instability at TAD boundaries. Our central hypothesis is that TAD boundaries with ultra-high CTCF density represent hotspots in the human genome susceptible to instability. To test this hypothesis, we propose experimental and computational studies to (1) quantitatively measure the role for CTCF density and double strand breaks on STR instability and (2) engineer CTCF occupancy to induce a functional change in STR expansion.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.