Pathobiology of Neurodegeneration in C9ORF72 Repeat Expansion

描述(申请人提供)：在这份题为“C9ORF72重复扩展中神经退行性变的病理生物学”的P01重新提交建议书中，我们寻求评估C9ORF72扩展重复的机制，C9ORF72重复是肌萎缩侧索硬化症(ALS)和前额颞叶痴呆(FTD)的最常见原因，以改善C9FTD/ALS患者的诊断和预后。我们组建了一支世界级的团队，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转录本和表观遗传学变化如何分别导致C9FTD/ALS毒性和单倍体不足方面取得了重大进展，从而发现重复扩增大小确实影响疾病严重程度，并确定了在C9FTD/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，在C9ORF72突变携带者的脑组织、成纤维细胞和血液中可以检测到组蛋白3赖氨酸9的异常甲基化。我们还确定TMEM106B是C9FTD/ALS疾病表型的第一个遗传修饰物。利用Mayo临床神经内科的优势，我们开始了对44个C9ALS家系的纵向研究，以确定扩张大小、组蛋白赖氨酸残基三甲基化、mRNA表达水平和TMEM106B基因是否与C9FTD/ALS的表型变异相关。此外，自那以后，我们已经生产并鉴定了在细胞和动物模型以及人体组织中检测五种重复相关的非ATG(RAN)翻译多肽[聚(GP)、聚(GA)、聚(GR)、聚(PA)和聚(PR)]的关键抗体。我们还提供了证据表明，泛素-2、tau和p62/序列小体存在于不同脑区和脊髓的神经元包涵体中，表明这些蛋白除了TDP-43外，可能在TDP-43病理的前颞叶变性(FTLD-TDP)的发病机制中发挥作用。我们提供的初步数据表明，用二甲基精氨酸抗体也可以检测到TDP-43阴性/C9RANT阳性的神经元包涵体，这表明了一种新的疾病机制，涉及非组蛋白蛋白甲基化。简而言之，我们的多学科研究将提高对C9ORF72相关神经退行性变的了解，识别潜在的生物标志物和治疗靶点，并开发引人注目的脑、生物液和活检资源，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.