DNA Damage and Neurodegeneration in Cockayne Syndrome

描述(申请人提供)：Cockayne综合征(CS)是一种进行性儿童神经退行性疾病，与DNA修复缺陷有关。两个基因，CsA和CSB，具体涉及CS障碍。这些基因参与了转录活性基因(转录偶联修复)中紫外线损伤的核苷酸切除修复(NER)。与人类患者相比，CS-a和Cs-b小鼠的神经系统症状要温和得多，但患癌症的风险更大，这在人类身上通常不明显。我们发现，将Cs-b小鼠与XP-c小鼠(基因组非转录区域NER有缺陷)杂交，可以增加两种基因纯合或杂合但不一定影响紫外线敏感性的动物的神经退行性变的严重程度和发病年龄。这导致了反映人类CS患者严重程度的小鼠品系，并可用作神经退行性变的模型，我们将与人类综合征进行详细比较。然而，并不是所有的CS患者的症状都很容易与修复缺陷相关，所以我们假设有其他与疾病相关的途径，特别是那些与CsA和CSB基因产物相关的泛素连接酶共同缺陷的下游结果。我们发现CSB缺陷导致细胞周期和抗血管生成基因和蛋白表达的改变，以及与发育受损和进行性神经变性相关的更多的细胞程序性死亡。因此，我们建议，在目标I中，我们将确定小鼠Cs-b x XP-c是否交叉概括了人类疾病的病理。我们将确定程序性细胞死亡的特定部位，以及浦肯野细胞丧失是主要事件还是由于祖细胞或相关细胞类型的丧失。我们将确定神经退行性变是否与细胞周期过早进入和慢性氧化损伤导致的细胞凋亡一致。在AIM II中，我们将检测来自我们的小鼠品系的人CS细胞和小鼠成纤维细胞的整体修复和转录偶联修复，以及小鼠神经细胞在活性氧损伤后的分化相关修复，以确定这些修复基因在神经退化中的作用。在目标III中，我们将确定我们已经确定的CS依赖泛素化的蛋白质靶标所扮演的角色，特别是那些过度表达可能具有病理后果的蛋白质靶标。我们将强调那些先前确定的靶点，如p21和15a1胶原蛋白，因为它们在发育和神经退行性变中发挥作用。这些研究的成功结束将扩大我们对神经退行性变机制的认识，并为开发CS患者的治疗方法奠定基础。

DESCRIPTION (provided by applicant): Cockayne syndrome (CS) is a progressive childhood neurodegenerative disorder associated with a DNA repair defect. Two genes, CSA and CSB, are specifically involved in the CS disorder. These genes are involved in nucleotide excision repair (NER) of ultraviolet damage (UV) in transcriptionally active genes (transcription coupled repair, TCP). Cs-a and Cs-b mice have much milder neurological symptoms than human patients, but a greater risk for cancer that is not usually evident in humans. We have found that crossing Cs-b mice with Xp-c mice, that are defective in NER of nontranscribed regions of the genome, increases the severity and reduces the age of onset of neurodegeneration in animals that are homozygous or heterozygous in both genes but without necessarily compromising UV sensitivity. This has resulted in mouse strains that reflect the range of severity of human CS patients and can be used as models of neurodegeneration that we will compare in detail with the human syndrome. Not all the symptoms of CS patients are however easily related to repair deficiencies, so we hypothesize that there are additional pathways relevant to the disease particularly those that are downstream consequences of a common defect in ubiquitin ligase associated with the CSA and CSB gene products. We have found that the CSB defect results in altered expression of cell cycle and anti-angiogenic genes and proteins, and more programmed cell death that are relevant to the impaired development and progressive neurodegeneration. We therefore propose that, in Aim I, we will determine whether the mouse Cs-b x Xp-c crosses recapitulate the pathology of the human disease. We will determine the specific sites of programmed cell death and whether Purkinje cell loss is a primary event or due to loss of progenitor or associated cell types. We will determine whether neurodegeneration is consistent with premature cell cycle entry and apoptosis from chronic oxidative injury. In Aim II, we will examine global and transcription coupled repair in human CS cells and mouse fibroblasts from our mouse strains and differentiation-associated repair in mouse cells of neuronal origin following damage from reactive oxygen, to identify the contributions of these repair genes to neurodegeneration. In Aim III we will determine the roles played by protein targets of CS-dependent ubiquitylation that we have identified, especially those whose over-expression may have pathological consequences. We will emphasize those targets previously identified, such as p21 and collagen 15a1, for their roles in development and neurodegeneration. Successful conclusion of these studies will expand our knowledge of mechanisms of neurodegeneration and lay groundwork for development of therapeutic approaches for CS patients.