Neuroinflammation and motor neuron loss in SMA

项目摘要 脊髓性肌萎缩症（SMA）是一种退行性疾病，是婴儿死亡的主要遗传原因 其特征在于脊髓中运动神经元的丧失、骨骼肌萎缩和死亡。SMA是由 通过运动神经元存活基因（SMN）的破坏或缺失，以及运动神经元存活基因（SMN）的大量减少， 然而，SMN丢失在疾病病理学中的具体作用仍不清楚。电流 治疗替代和/或增加患者的SMN水平，尽管这种策略在很大程度上是成功的， 令人惊讶的是，即使在症状前阶段开始治疗，也不能治愈。运动神经元的丧失 SMA的发展，但运动神经元丢失的机制尚不清楚。越来越多的证据 来自我们小组和其他人的研究表明，星形胶质细胞有助于复杂的SMA表型和运动神经元， 损失我们发现SMA星形胶质细胞（i）表现出改变的形态，（ii）缺乏生长因子的产生，（iii） 具有异常MAPK信号传导，（iv）具有增加的NFκB核定位，（v）显示异常上调 GATA 6表达的差异，（vi）表现出增加的细胞因子表达，（vii）差异表达和产生 microRNA，和（viii）在小鼠和人iPSC模型中直接诱导运动神经元损失。SMA患者 死后组织也表现出星形胶质细胞增生和细胞因子表达增加， 实验结果的确认。SMA小胶质细胞也显示出改变的激活状态、蛋白水解活性 和吞噬作用，我们最近的数据表明，星形胶质细胞进一步诱导小胶质细胞功能障碍。 值得注意的是，星形胶质细胞异常发生在疾病过程的非常早期，在明显的运动神经元损失之前， 小胶质细胞功能障碍，使我们在概念上提出了星形胶质细胞驱动疾病的前提- 改变SMA中的神经炎症级联反应。根据我们广泛的已发表和初步数据，我们 假设GATA 6介导细胞因子级联反应是星形胶质细胞功能障碍和疾病的基础 病理通过接触依赖和独立的机制。在这里，我们将利用我们广泛的 在SMA、iPSC疾病建模、基因治疗和表面蛋白质组学方面的专业知识， 导致星形胶质细胞功能障碍的机制以及对小胶质细胞功能和运动神经元的下游影响 生存合作团队在拟议实验的各个方面都经验丰富， 对我们对健康和疾病中人类神经胶质-神经元相互作用的基本理解产生影响。 长期目标是确定新型非SMN治疗靶点以补充目前批准的治疗靶点 治疗，和拟议的实验朝着实现这一目标迈出了巨大的步伐。

PROJECT SUMMARY Spinal muscular atrophy (SMA), a leading genetic cause of infant mortality, is a degenerative disease characterized by loss of motor neurons in the spinal cord, skeletal muscle atrophy, and death. SMA is caused by the disruption or deletion of the survival motor neuron (SMN) gene and a substantial reduction in the associated SMN protein; however, the specific role SMN loss plays in disease pathology is still unclear. Current therapies replace and/or increase SMN levels in patients, and although this strategy is largely successful, it is surprisingly not a cure even when treatment initiates in pre-symptomatic stages. Motor neuron loss is essential for the development of SMA, but the mechanisms underlying motor neuron loss is unknown. Growing evidence from our group and others suggests that astrocytes contribute to the complex SMA phenotype and motor neuron loss. We have found that SMA astrocytes (i) exhibit altered morphology, (ii) lack growth factor production, (iii) have aberrant MAPK signaling, (iv) have increased nuclear localization of NFκB, (v) show aberrant upregulation of GATA6 expression, (vi) exhibit increased cytokine expression, (vii) differentially express and produce microRNAs, and (viii) directly induce motor neuron loss in mouse and human iPSC models. SMA patient postmortem tissues also demonstrate astrogliosis and increased cytokine expression providing important confirmation of the experimental results. SMA microglia also show altered activation states, proteolytic activity and phagocytosis, and our recent data demonstrate that astrocytes further induce microglial malfunction. Notably, astrocyte abnormalities occur very early in the disease process, prior to overt motor neuron loss and microglial malfunction leading us to conceptually advance the premise that astrocytes drive the disease- modifying neuroinflammatory cascade in SMA. Based on our extensive published and preliminary data, we hypothesize that a GATA6-mediated cytokine cascade underlies astrocyte malfunction and disease pathology via both contact dependent and independent mechanisms. Here we will leverage our extensive expertise in SMA, iPSC disease modeling, gene therapy, and surface proteomics to elucidate the molecular mechanisms causing astrocyte dysfunction and the downstream impacts on microglial function and motor neuron survival. The collaborative team is highly experienced in all aspects of the proposed experiments and is poised to make impacts on our foundational understanding of human glial-neuron interactions in health and disease. The long-term objective is to identify novel non-SMN therapeutic targets to supplement currently approved therapies, and the proposed experiments make great strides toward achieving that goal.