Elucidating the Role of Dynamic X-Chromosome Inactivation Maintenance in the Pathogenesis of Systemic Sclerosis

项目摘要/摘要： 系统性硬化症是一种主要影响女性的全身性自身免疫性疾病。 由于皮肤和内脏纤维化，发病率和死亡率很高。这种现象的分子起源 显著的女性偏见及其与SSc发病机制的核心方面的关系，包括免疫紊乱。 血管病变、多器官纤维化和血管病变，目前仍不清楚。虽然已知的遗传风险变异也是如此- 与SSC相关的低同卵双胞胎符合率促使人们对表观基因的作用进行了研究。 磁性失调在其发病机制中的作用。重要的是，X染色体包含几个促炎性和 促纤维化基因，其在女性中的适当表达在一定程度上是通过X-chro-DNA的表观遗传学调节的。 嵌合体失活(XCI)，一种女性特有的表观遗传机制，使两条X染色体中的一条沉默 为了使XX女性和XY男性的X连锁基因剂量相等。XCI在体细胞中维持 通过丰富在非活动X染色体(XI)上的各种表观遗传修饰，包括长的 非编码RNA XIST和额外的异染色组蛋白修饰。我们最近发现XCI 人类和小鼠T细胞的维持都是“动态的”。在“动态XCI维护”中，XIST RNA和 在静息T细胞中，异色标记在细胞学上从XI中消失，随后重新定位到 依赖于体外细胞激活。我们发现T细胞的动态XCI维持受到损害 女性狼疮，另一种女性偏向的自身免疫性疾病，与X连锁基因异常相关 来自习的表情。基于T细胞在SSC介导的病理中的公认作用， X连锁的促炎和促纤维化基因，这些基因中的许多在 和我们的初步数据，我们假设T细胞中动态XCI维持受损是一种 SSC的致病机制相应地导致了观察到的女性偏见。在目标1中，我们将使用 单细胞成像以确定患有SSc的女性T细胞的XCI维持是否受损。我们会 将这些分析与转录研究相结合，以确定XI对观察到的X连锁的贡献 基因表达谱。在目标2中，我们将在一种新的受损的小鼠模型中诱导硬皮病样疾病。 XCI维持确定T细胞中XCI维持受损如何影响T细胞特异性转录 增加SSc相关器官纤维化易感性的方案。总体而言，这项工作有可能 确定SSC中女性偏见的一种新的表观遗传机制，并同时确定哪些X-连锁 在纤维化疾病的发展过程中，基因在T细胞中异常表达。这些发现将 提高我们对生物性行为如何在SSC和相关女性的发病机制中的作用的理解- 对自身免疫性疾病有偏见，并可能最终发现治疗SSc的新疗法。

Project Summary/Abstract: Systemic sclerosis (SSc) is a systemic autoimmune disease that predominantly affects women and is associated with significant morbidity and mortality due to fibrosis of the skin and internal organs. The molecular origin of this striking female bias and its relationship to core aspects of the pathogenesis of SSc, including immune dysregu- lation, multiorgan fibrosis, and vasculopathy, remains unclear. While there are known genetic risk variants asso- ciated with SSc, the low monozygotic twin concordance rate has prompted investigation into the role of epige- netic dysregulation in its pathogenesis. Importantly, the X-chromosome contains several proinflammatory and profibrotic genes, and their appropriate expression in females is epigenetically regulated in part through X-chro- mosome inactivation (XCI), a female-specific epigenetic mechanism that silences one of the two X chromosomes in order to equalize X-linked gene dosage between XX females and XY males. XCI is maintained in somatic cells by a variety of epigenetic modifications that are enriched on the inactive X chromosome (Xi), including the long noncoding RNA XIST and additional heterochromatic histone modifications. We recently discovered that XCI maintenance in T-cells from both humans and mice is “dynamic.” In “dynamic XCI maintenance”, XIST RNA and heterochromatic marks are cytologically absent from the Xi in resting T-cells and subsequently relocalize to the Xi upon in vitro cellular activation. We have found that dynamic XCI maintenance is impaired in T-cells from women with lupus, another female-biased autoimmune disease, and is associated with aberrant X-linked gene expression from the Xi. Based on the well-established role of T-cells in SSc-mediated pathology, the number of X-linked proinflammatory and profibrotic genes, the aberrantly increased expression of many of these genes in SSc T-cells, and our preliminary data, we hypothesize that impaired dynamic XCI maintenance in T-cells is a pathogenic mechanism in SSc that accordingly contributes to the observed female bias. In Aim 1, we will use single cell imaging to determine whether XCI maintenance is impaired in T-cells from females with SSc. We will couple these analyses with transcriptomic studies to determine the contribution of the Xi to the observed X-linked gene expression profile. In Aim 2, we will induce scleroderma-like disease in a novel mouse model of impaired XCI maintenance to determine how impaired XCI maintenance in T-cells impacts T-cell-specific transcriptional programs conferring susceptibility to fibrosis in SSc-relevant organs. Collectively, this work has the potential to identify a novel epigenetic mechanism of female bias in SSc and will simultaneously identify which X-linked genes become aberrantly expressed in T-cells during the development of fibrotic disease. These findings will improve our understanding of how biological sex contributes to the pathogenesis of SSc and related female- biased autoimmune disease and may enable the eventual discovery of new therapies for SSc.