DNA Damage and Neurodegeneration in Cockayne Syndrome

描述（由申请人提供）：Cockayne综合征（CS）是一种与DNA修复缺陷相关的进行性儿童神经退行性疾病。两个基因，CSA和CSB，特别涉及CS疾病。这些基因参与转录活性基因中紫外线损伤（UV）的核苷酸切除修复（NER）（转录偶联修复，TCP）。Cs-a和Cs-b小鼠的神经系统症状比人类患者轻得多，但患癌症的风险更大，这在人类中通常不明显。我们已经发现，将基因组非转录区域的NER有缺陷的Cs-b小鼠与Xp-c小鼠杂交，增加了两种基因均为纯合或杂合的动物神经变性的严重程度并降低了神经变性的发病年龄，但不一定会损害UV敏感性。这导致小鼠品系反映了人类CS患者的严重程度范围，并且可以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，并非所有CS患者的症状都容易与修复缺陷相关，因此我们假设存在与疾病相关的其他途径，特别是那些与CSA和CSB基因产物相关的泛素连接酶常见缺陷的下游后果。我们已经发现，CSB缺陷导致细胞周期和抗血管生成基因和蛋白质的表达改变，以及与发育受损和进行性神经变性相关的更多程序性细胞死亡。因此，我们提出，在目的I中，我们将确定小鼠Cs-b x Xp-c杂交是否重现人类疾病的病理学。我们将确定程序性细胞死亡的具体部位，以及浦肯野细胞丢失是原发性事件还是由于祖细胞或相关细胞类型的丢失。我们将确定神经退行性变是否与慢性氧化损伤引起的过早进入细胞周期和细胞凋亡一致。在目标II中，我们将研究全球和转录偶联修复人类CS细胞和小鼠成纤维细胞从我们的小鼠品系和分化相关的修复神经元来源的小鼠细胞损伤后的活性氧，以确定这些修复基因的神经变性的贡献。在目标III中，我们将确定我们已经确定的CS依赖性泛素化的蛋白质靶点所起的作用，特别是那些过度表达可能具有病理后果的蛋白质。我们将强调那些以前确定的目标，如p21和胶原蛋白15 a1，他们在发展和神经退行性变的作用。这些研究的成功将扩大我们对神经退行性变机制的认识，并为CS患者的治疗方法的发展奠定基础。

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.