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

基本信息

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
项目类别：
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&apos 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

项目摘要

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.

额颞叶痴呆（FTD）是继阿尔茨海默病之后第二常见的遗传性痴呆类型 FTD 是由额叶和颞叶细胞进行性神经变性引起的。 C9orf72 基因第一个内含子中的 GGGGCC (G4C2) 序列的扩展最为明显。 FTD 的常见遗传原因，约 25% 的病例是由 FTD 扩展的机制造成的。 G4C2 序列导致特定神经元的神经变性尚不完全清楚。在有义和反义方向上转录，两条 RNA 链都可以经历一种不寻常的类型翻译称为有义和反义重复相关非 AG 依赖翻译 (RANT)。 G4C2 RNA 产生五种不同的二肽重复蛋白 (DPR)，其中两种（PR 和 GR）赋予强为了更好地了解 C9orf72 介导的 FTD 的发病机制，我们生成表达纯 DPR 的线虫模型，PR 和 GR 对蠕虫均有毒并引起。为了定义基因和引起毒性的途径，我们进行了无偏见的遗传学研究。抑制筛选并发现了几个高度保守的基因，可以高度阻断 PR50 毒性。保守的抑制子是核 E3 连接酶接头 SPOP 自 SPOP 以来，SPOP 在癌症中得到了广泛的研究。错义突变是前列腺癌和子宫内膜癌的主要遗传原因，但 SPOP 却并非如此。迄今为止，SPOP 在 DPR 毒性中的作用一直被认为与神经退行性疾病有关。 SPOP 基因敲除和 SPOP 小分子抑制剂均可阻断 DPR 对哺乳动物原代细胞的毒性癌症中的一个主要 SPOP 靶点是 BRD2/3/4，它们是含有溴结构域的转录因子。我们发现抑制 BRD 同源物 bet-1 会抑制 SPOP 突变体的能力。基于这些发现，我们研究了 SPOP 途径，即目前正在用于治疗癌症，也可能是 C9 神经退行性病理学的基础为了检验这一假设，我们将：1）确定 DPR 是否直接与 SPOP 相互作用来调节。已知的病理途径，例如有缺陷的核运输和应激颗粒的形成；2) 描绘出 SPOP、BRD 和可能的其他底物介导 DPR 毒性的机制；以及 3) 确定 SPOP 是否存在；是哺乳动物神经元中针对 DPR 的神经保护的“可药物”靶标。使用多种方法和实验模型系统与 C9 疾病相关的新途径。这种新型泛素化系统的发现可能会为这种无法治愈的疾病带来新的治疗见解失智。