THE ROLE OF FAN1 NUCLEASE IN KIDNEY AND DIGESTIVE SYSTEM HEALTH AND FUNCTION

项目摘要 DNA损伤的忠实修复对于维持基因组稳定性至关重要。缺乏修复或不适当的DNA 修复可导致突变、不受控制的细胞生长、细胞死亡或生长停滞。我们已经确认了FAN 1 核酸酶作为维持基因组稳定性的潜在效应物。FAN 1与interstrand有关 交联（ICL）修复作为负责脱钩和释放交联或受损DNA的核酸酶 基地ICL修复蛋白的突变通常会导致骨髓衰竭或癌症;然而，ICL修复蛋白的突变也会导致骨髓衰竭或癌症。 FAN 1引起一种称为巨核间质性肾炎（KIN）的慢性肾脏疾病。KIN患者 最终发展为需要透析或肾移植的肾衰竭。的基本机制， FAN 1突变如何引起KIN仍然是未知的。肾功能不全可能是通过 内源性产生的ICL的修复缺陷，或者可能是由于FAN 1的独立功能， 典型ICL修复。最近的研究表明，FAN 1的突变赋予了对糖尿病的更大易感性。 结肠直肠癌和胰腺癌，并且是三核苷酸重复扩增疾病的遗传修饰剂， 是亨廷顿病总之，这些发现表明，FAN 1可能具有细胞外的功能。 典型ICL修复。在拟议的研究中，我们的目标是辨别FAN 1的各种分子机制， 在体内起作用以及鉴定驱动KIN的致病性内源性病变。在目标1中，目标是使用 一个多管齐下的方法确定FAN 1在体细胞重复不稳定性中的作用。使用小鼠模型， 三核苷酸重复扩增，我们将评估Fan 1的缺失是否驱动组织中的重复扩增， 特定的方式或通过生殖系遗传。我们还将确定FAN 1是否影响微卫星重复 不稳定性（MSI），在结肠癌中观察到的常见表型。在目标2中，我们将确定 FAN 1在DNA复制中的作用，KIN中多倍化的机制，以及肿瘤发生的易感性。 我们将使用一个Fan 1基因敲除小鼠模型，重现人类KIN表型。通过分离细胞， 在存在/不存在DNA复制应激的情况下进行各种DNA复制测定 或损伤，我们将阐明Fan 1在体内的作用。我们还将进行实验， 了解FAN 1在KIN和肿瘤发生中的作用。最后，在目标3中，我们将识别致病病变 在没有FAN 1的情况下驾驶KIN。该提案的调查结果有可能揭示 FAN 1如何抑制肾脏和消化系统功能障碍的基本原理。

Project Summary The faithful repair of DNA damage is critical to maintain genome stability. Lack of repair or inappropriate DNA repair can lead to mutations, uncontrolled cell growth, cell death, or growth arrest. We have identified FAN1 nuclease as a potential effector for maintaining genome stability. FAN1 has been implicated in interstrand crosslink (ICL) repair as a nuclease responsible for unhooking and releasing the crosslinked or damaged DNA base. Mutations in ICL repair proteins usually give rise to bone marrow failure or cancer; however, mutations in FAN1 cause a form of chronic kidney disease termed Karyomegalic Interstitial Nephritis (KIN). KIN patients ultimately develop renal failure requiring dialysis or kidney transplantation. The underlying mechanism as to how FAN1 mutations gives rise to KIN still remains unknown. It may be that kidney dysfunction occurs through defective repair of endogenously produced ICLs or it could be due to independent functions of FAN1 outside of canonical ICL repair. More recently, it was shown that mutations in FAN1 confer a greater susceptibility to colorectal and pancreatic cancer, and are genetic modifiers for trinucleotide repeat expansion diseases, such as Huntington's disease. Together, these findings suggest that FAN1 may have functions outside of the canonical ICL repair. In the proposed research, we aim to discern the various molecular mechanisms of FAN1 function in vivo as well as to identify the causative endogenous lesions driving KIN. In Aim 1, the goal is to use a multi-pronged approach determine the role of FAN1 in somatic repeat instability. Using a mouse model of trinucleotide repeat expansion we will assess if the absence of Fan1 drives repeat expansion in a tissue- specific manner or through germline inheritance. We will also determine if FAN1 affects microsatellite repeat instability (MSI), a common phenotype observed in colon cancer. In Aim 2, we will determine the function of FAN1 in DNA replication, the mechanism of polyploidization in KIN, and the predisposition to tumorigenesis. We will use a Fan1 knockout mouse model that recapitulates the human KIN phenotype. By isolating cells from this model and performing various DNA replication assays in the presence/absence of DNA replication stress or damage, we will shed light on the in vivo role for Fan1. We will also perform experiments to better understand the role for FAN1 in KIN and tumorigenesis. Finally, in Aim 3 we will identify the causative lesion(s) driving KIN in the absence of FAN1. The findings from this proposal have the potential to uncover the fundamental principles of how FAN1 acts to suppress dysfunction of the kidney and digestive system.