Pathobiology of Neurodegeneration in C9ORF72 Repeat Expansion

描述（由申请人提供）： 在题为“C9 ORF 72重复序列扩增中神经变性的病理生物学”的P01重新提交提案中，我们试图评估C9 ORF 72扩增重复序列的机制，C9 ORF 72扩增重复序列是肌萎缩侧索硬化症（ALS）和前颞叶痴呆（FTD）的最常见原因，以改善c9 FTD/ALS患者的诊断和预后。我们已经组建了一个世界级的团队，结合了神经学，遗传学，神经病理学和细胞生物学的专业知识，密切合作，并拥有所有资源。我们在阐明扩增的重复RNA转录物和表观遗传学变化如何分别驱动c9 FTD/ALS的毒性和单倍不足方面取得了重大进展，发现重复扩增大小确实影响疾病严重程度，并鉴定了c9 FTD/ALS患者血液中可检测到的潜在生物标志物。我们现在提出的证据表明，组蛋白3在赖氨酸9的异常甲基化是可检测的脑组织，成纤维细胞和血液中的C9 ORF 72突变携带者。我们还鉴定了TMEM 106 B作为C9 FTD/ALS中疾病表型的第一个遗传修饰因子。利用马约临床神经科的优势，我们已经开始对44个C9 ALS家系进行纵向研究，以确定扩增大小、组蛋白赖氨酸残基的三甲基化、mRNA表达水平和TMEM 106 B基因型是否与c9 FTD/ALS的表型变异性相关。此外，我们已经生产并表征了用于检测细胞和动物模型以及人体组织中五种重复相关非ATG（RAN）翻译肽[poly（GP），poly（GA），poly（GR），poly（PA）和poly（PR）]中每一种的关键抗体。我们还提供了证据表明，泛素-2，tau蛋白和p62/隔离体存在于各种脑区和脊髓的神经元包涵体中，表明这些蛋白质，除了TDP-43，可能在前颞叶变性与TDP-43病理（FTLD-TDP）的发病机制中发挥作用。我们提供的初步数据表明，TDP-43阴性/C9 RANT阳性神经元包涵体也可以用二甲基精氨酸抗体检测，这表明一种新的疾病机制涉及非组蛋白甲基化。简而言之，我们的多学科研究将提高对C9 ORF 72相关神经变性的理解，确定潜在的生物标志物和治疗靶点，并开发引人注目的大脑，生物流体和活检资源，以帮助未来的药物发现。

DESCRIPTION (provided by applicant): In this P01 resubmission proposal entitled "Pathobiology of Neurodegeneration in C9ORF72 Repeat Expansion," we seek to evaluate the mechanisms of C9ORF72 expanded repeats, the most common cause of amyotrophic lateral sclerosis (ALS) and front temporal dementia (FTD), to improve the diagnosis of and prognosis for patients suffering from c9FTD/ALS. We have assembled a world-class team combining expertise in neurology, genetics, neuropathology, and cell biology that has worked closely together and has all resources in place. Our significant progress to elucidate how expanded repeat RNA transcripts and epigenetic changes may respectively drive toxicity and haploinsufficiency in c9FTD/ALS has led to the discovery that repeat expansion size does affect disease severity, and the identification of a potential biomarker detectable in blood of c9FTD/ALS patients. We now present evidence that aberrant methylation of histone 3 at lysine 9 is detectable in brain tissue, fibroblasts and blood of C9ORF72 mutation carriers. We also identified TMEM106B as the first genetic modifier of disease phenotype in C9FTD/ALS. In drawing upon the strengths of the Mayo Clinic Neurology Department, we have begun longitudinal studies of 44 C9ALS pedigrees to determine whether expansion size, tri-methylation of histone lysine residues, mRNA expression levels and TMEM106B genotypes, correlate with phenotypic variability in c9FTD/ALS. In addition, we have since produced and characterized antibodies critical for detecting each of the five repeat-associated non-ATG (RAN) translation peptides [poly(GP), poly(GA), poly(GR), poly(PA) and poly(PR)] in cell and animal models as well as human tissue. We also provide evidence that ubiquilin-2, tau and p62/sequestosome are present in neuronal inclusions in various brain regions and spinal cord, indicating that these proteins, in addition to TDP-43, may play a role in pathogenesis of front temporal lobar degeneration with TDP-43 pathology (FTLD-TDP). We provide preliminary data that TDP-43-negative/C9RANT-positive neuronal inclusions can also be detected with antibodies to dimethylarginine, suggesting a new disease mechanism involving non-histone protein methylation. Simply put, our multi-disciplinary studies will improve understanding of C9ORF72-related neurodegeneration, identify potential biomarkers and therapeutic targets, and develop a compelling brain, biofluid and biopsy resource to aid future drug discovery.