Neuroinflammation and motor neuron loss in SMA

项目总结 脊髓性肌萎缩症(SMA)是一种退行性疾病，是导致婴儿死亡的主要遗传原因。 以脊髓运动神经元丧失、骨骼肌萎缩和死亡为特征。SMA是由 通过破坏或缺失存活运动神经元(SMN)基因和大幅减少 相关的SMN蛋白；然而，SMN丢失在疾病病理中所起的具体作用仍不清楚。当前 治疗取代和/或提高患者的SMN水平，虽然这种策略在很大程度上是成功的，但 令人惊讶的是，即使在症状前期开始治疗，也不能治愈。运动神经元丢失是必不可少的 对于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，星形胶质细胞对复杂的SMA表型和运动神经元有贡献 损失。我们发现SMA星形胶质细胞(I)形态改变，(II)缺乏生长因子产生，(III) 有异常的MAPK信号，(Iv)增加了核转录因子κB的核定位，(V)表现为异常上调 在GATA6表达中，(Vi)细胞因子表达增加，(Vii)差异表达和产生 在小鼠和人类IPSC模型中，(Viii)直接导致运动神经元丢失。SMA患者 尸检组织也表现为星形胶质细胞增生和细胞因子表达增加，提供了重要的 对实验结果进行了验证。SMA小胶质细胞也表现出激活状态、蛋白分解活性的改变 和吞噬，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丢失和 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- 改善SMA的神经炎性级联反应。根据我们广泛公布的初步数据，我们 假设GATA6介导的细胞因子级联是星形胶质细胞功能障碍和疾病的基础 通过接触依赖和独立机制的病理学。在这里，我们将利用我们广泛的 在SMA、IPSC疾病模型、基因治疗和表面蛋白质组学方面的专业知识，以阐明分子 星形胶质细胞功能障碍的机制及其下游对小胶质细胞功能和运动神经元的影响 生死存亡。协作团队在提议的实验的所有方面都非常有经验，并且准备好了 对我们在健康和疾病中对人类神经胶质细胞-神经元相互作用的基础理解产生影响。 长期目标是确定新的非SMN治疗靶点，以补充目前批准的 疗法，拟议的实验在实现这一目标方面取得了长足的进步。

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.