The Functional Role of RBM45 in Gene Expression and Neurodegeneration

描述(申请人提供)：肌萎缩侧索硬化症(ALS)是一种进行性的，不可避免的致命的神经退行性疾病。在病理学上，ALS的特征是皮质脊髓束运动神经元的死亡，导致许多衰弱的症状，最终导致瘫痪和死亡。对ALS神经退变的分子机制的研究表明，RNA加工受损和RNA结合蛋白在细胞死亡中的胞质内聚集。我们最近对ALS患者进行了一项基于脑脊液(CSF)的蛋白质组学研究，并确定新的RNA结合蛋白RBM45是一个可能的疾病生物标记物。通过对ALS患者脊髓组织的免疫组织化学进一步研究RBM45，发现运动神经元中RBM45阳性的胞浆内包涵体在外观上与其他ALS相关RNA结合蛋白TDP-43和FUS的胞浆内包涵体相似。我们现在试图通过研究RBM45的正常功能以及它在神经退行性疾病病理中的贡献(S)来扩展这些初步观察。为此，我们将首先评估RBM45的过度表达和敲除如何影响两个细胞系的形态、包涵体的形成和生存能力。我们还将过度表达一种自然产生的蛋白质亚型，缺乏假定的核定位信号，以确定该变体在体外聚集的倾向。这项提议的下一个目标是不了解RBM45在细胞对压力的反应中扮演什么角色(如果有的话)。细胞将通过亚砷酸盐处理而受到压力，并将再次测量含有RBM45的包涵体的形态、数量和细胞活力。我们还将检查细胞中RBM45翻译后修饰的变化，与其他RNA结合蛋白的共定位，以及整合到应激颗粒中，以解决RBM45在应激过程中的功能。在这项提议的第二阶段，将通过UV交联和免疫沉淀结合RNA-Seq来定义RBM45基因靶点。接下来，我们将评估RBM45在基因表达调控和选择性剪接中的贡献。在这些实验中，RBM45将通过shRNA从细胞中去除，基因表达和外显子剪接的变化将使用外显子连接敏感微阵列来确定。在这项提案的最后阶段，我们将尝试使用人类死后组织进行免疫组织化学和共聚焦显微镜检查，将AIMS 1和AIMS 2中的发现与人类神经退行性疾病联系起来。将评估组织中RBM45的脑区特异性和细胞类型特异性表达，包涵体，以及与其他ALS和应激反应相关蛋白的共存。总的来说，这些实验将提供有关RBM45在正常细胞功能和疾病中所起作用的新信息。

DESCRIPTION (provided by applicant): Amyotrophic lateral sclerosis (ALS) is a progressive, inevitably fatal neurodegenerative disorder. Pathologically, ALS is characterized by the death of motor neurons of the corticospinal tract, resulting in a numerous debilitating symptoms culminating with paralysis and death. Research into the molecular mechanisms of ALS neurodegeneration has implicated impaired RNA processing and intracytoplasmic aggregation of RNA binding proteins in cell death. We recently performed a cerebrospinal fluid (CSF)-based proteomics study of ALS patients and identified the novel RNA binding protein RBM45 as a putative disease biomarker. Further investigation of RBM45 via immunohistochemistry of ALS patient spinal cord tissue revealed RBM45-positive intracytoplasmic inclusions in motor neurons similar in appearance to those containing the other ALS-associated RNA binding proteins TDP-43 and FUS. We now seek to extend these preliminary observations by studying the normal function of RBM45 as well as its contribution(s) to neurodegenerative disease pathology. To do so, we will first assess how overexpression and knockdown of RBM45 influences the morphology, formation of inclusions, and viability of two cell lines. We will also overexpress a naturally-occurring isoform of the protein lacking a putative nuclear localization signal to determine the propensity of this variant to aggregate in vitro. The next goal of this proposal is t understand what role (if any) RBM45 has in the cellular response to stress. Cells will be stressed via treatment with arsenite and the morphology, number of RBM45-containing inclusions, and cell viability will again be measured. We will also examine the cells for changes in RBM45 post-translational modifications, colocalization with other RNA binding proteins, and incorporation into stress granules to address the function of RBM45 during stress. In the second phase of this proposal, RBM45 gene targets will be defined via UV cross-linking and immunoprecipitation in conjunction with RNA-Seq. We will next assess the contribution of RBM45 to the regulation of gene expression and alternative splicing. For these experiments, RBM45 will be depleted from cells via shRNA and the changes in gene expression and exon splicing will be determined using exon junction- sensitive microarrays. In the last phase of this proposal, we will attempt to link findings obtained in aims 1 and 2 to human neurodegenerative disease using human post-mortem tissue for immunohistochemistry and confocal microscopy. Tissues will be evaluated for brain region-specific and cell type-specific expression of RBM45, inclusions, and colocalization with other ALS- and stress response-associated proteins. Collectively, these experiments will provide new information about the role of RBM45 in normal cell function and disease.