Defining mechanisms underlying C9orf72-associated frontotemporal dementia with C. elegans and mammalian models

用线虫和哺乳动物模型定义 C9orf72 相关额颞叶痴呆的机制

• 批准号: 10342721
• 负责人: Robert G Kalb
• 金额: $ 76.69万
• 依托单位: NORTHWESTERN UNIVERSITY AT CHICAGO
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-02-01 至 2027-01-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10342721
• 关键词: Ablation; Address; Alzheimer' s Disease; Antineoplastic Agents; Arginine; BRD2 gene; Biochemical; Biological; Biological Assay; Biological Models; Bromodomain; C9ORF72; CUL3 gene; Caenorhabditis elegans; Cell model; Cells; Cerebral cortex; Cullin Proteins; Degradation Pathway; Dementia; Development; Diagnosis; Dipeptides; Disease; Endometrial Carcinoma; Exhibits; Experimental Models; Frontotemporal Dementia; Gene Expression; Genes; Genetic; Genetic Screening; Genetic Transcription; Glycine; Homologous Gene; Inherited; Introns; Label; Lead; Link; Malignant Neoplasms; Malignant neoplasm of prostate; Mediating; Missense Mutation; Modeling; Mutation; Nerve Degeneration; Neurodegenerative Disorders; Neurons; Nuclear; Pathogenesis; Pathologic; Pathology; Pathway interactions; Patients; Peptides; Phenotype; Play; Proline; Property; Proteins; Proteomics; RNA; Renal carcinoma; Role; System; Temporal Lobe; Testing; Toxic effect; Transcription Regulatory Protein; Translations; Ubiquitination; base; cancer therapy; druggable target; frontal lobe; frontotemporal lobar dementia-amyotrophic lateral sclerosis; induced pluripotent stem cell; inhibitor; insight; knock-down; mutant; neuroprotection; novel; novel therapeutics; nucleocytoplasmic transport; programs; progressive neurodegeneration; protein degradation; small molecule; small molecule inhibitor; stress granule; targeted treatment; transcriptome sequencing; ubiquitin-protein ligase

Frontotemporal dementia (FTD) is the second most common type of inherited dementia following Alzheimer’s disease. FTD is caused by the progressive neurodegeneration of cells in the frontal and temporal lobe of the cerebral cortex. Expansion of a GGGGCC (G4C2) sequence in the first intron of the C9orf72 gene is the most common genetic cause of FTD and is responsible for ~25% of cases. The mechanisms by which expansion of the G4C2 sequence lead to neurodegeneration of specific neurons is incompletely understood. G4C2 RNA is transcribed in both sense and antisense directions and both RNA strands can undergo an unusual type of translation called Repeat Associated non-AG dependent translation (RANT). RANT of the sense and antisense G4C2 RNA produces five distinct dipeptide repeat proteins (DPRs), two of which (PR and GR) confer strong toxicity in multiple model systems. To better understand the pathogenesis of C9orf72-mediated FTD, we generated C. elegans models expressing pure DPRs. Both PR and GR were toxic in worms and caused neurodegeneration. To define genes and pathways causing toxicity, we performed an unbiased genetic suppressor screen and discovered several highly conserved genes that blocked PR50 toxicity. One highly conserved suppressor is the nuclear E3 ligase adaptor SPOP. SPOP is widely studied in cancer since SPOP missense mutations are a major genetic cause of prostate and endometrial cancer. However, SPOP has never been linked to a neurodegenerative disease until now. The role of SPOP in DPR toxicity is conserved, since both SPOP genetic knockdown and an SPOP small molecule inhibitor blocks DPR toxicity in mammalian primary neurons. One major SPOP target in cancer is BRD2/3/4, which are bromodomain-containing transcriptional regulatory proteins. We found that inhibition of the BRD homolog bet-1 suppresses the ability of SPOP mutants to protect against DPR toxicity. Based on these findings, we hypothesize that the SPOP pathway, which is currently being targeted for the treatment of cancer, may also underlie neurodegenerative pathology in C9 disease. To test this hypothesis, we will: 1) determine whether DPRs directly interact with SPOP to modulate known pathological pathways, such as defective nuclear transport and stress granule formation; 2) delineate the mechanism by which SPOP, BRD, and possibly other substrates mediate DPR toxicity; and 3) determine if SPOP is a ‘druggable’ target for neuroprotection against DPRs in mammalian neurons. Our studies will interrogate a novel pathway associated with C9 disease using a diversity of approaches and experimental model systems. The discovery of this novel ubiquitination system could lead to new therapeutic insights for this incurable form of dementia.

额颞痴呆（FTD）是继阿尔茨海默氏症之后的第二常见遗传性痴呆症类型 疾病。 FTD是由细胞在额叶和临时叶中的进行性神经变性引起的 大脑皮层。 C9orf72基因的第一个内含子中GGGGCC（G4C2）序列的扩展是最多的 FTD的常见遗传原因，造成约25％的病例。扩展的机制 G4C2序列导致特定神经元的神经变性尚不完全理解。 G4C2 RNA是 从意义和反义方向转录和反义方向以及两个RNA链都可以经历不寻常的类型 翻译称为重复相关的非AG依赖性翻译（rant）。意义和反义 G4C2 RNA产生五种不同的二肽重复蛋白（DPR），其中两个（PR和GR）会议强 多种模型系统中的毒性。为了更好地了解C9orf72介导的FTD的发病机理，我们 产生的秀丽隐杆线虫模型表达纯DPR。 PR和GR在蠕虫中都是有毒的，引起了 神经变性。为了定义引起毒性的基因和途径，我们进行了无偏的通用 抑制剂筛查并发现了几个高度组成的基因，这些基因阻断了PR50毒性。一个高度 保守的抑制剂是核E3连接酶适配器旋转。由于Spop，Spop广泛研究了癌症 错义突变是前列腺癌和子宫内膜癌的主要遗传原因。但是，Spop从来没有 到目前为止，我们与神经退行性疾病有关。 SPOP在DPR毒性中的作用是保守的，因为 SPOP遗传敲低和汤匙小分子抑制剂阻滞了哺乳动物原发性的DPR毒性 神经元。癌症中一个主要的汤匙目标是BRD2/3/4，它是含溴脱域的转录 调节蛋白。我们发现抑制BRD同源物BET-1抑制了SPOP突变体的能力 防止DPR毒性。基于这些发现，我们假设Spop途径是 目前正在针对癌症治疗，在C9中也可能是神经退行性病理的基础 疾病。要检验该假设，我们将：1）确定DPR是否直接与SPOP相互作用以调节 已知的病理途径，例如有缺陷的核转运和应力颗粒形成； 2）描述 SPOP，BRD和其他可能底物介导DPR毒性的机制； 3）确定是否吐 是针对哺乳动物神经元中DPRS神经保护的“可药物”靶标。我们的研究将询问 使用多种方法和实验模型系统与C9疾病相关的新途径。 这种新颖的泛素化系统的发现可能会导致这种无法治愈的形式的新治疗见解 失智。