The Immunopathogenic role of XIST in Sjogren's Syndrome

项目摘要/摘要 干燥综合征(SS)是一种全身性自身免疫性疾病，主要影响女性，但 造成这种强烈性别偏见的机制尚不清楚。X染色体被认为与 女性对SS等自身免疫性疾病的易感性增加，令人信服的证据表明 X染色体异常失活(XCI)可能起致病作用。XCI发生在开发过程中 使男性和女性之间的X连锁基因剂量正常化，这取决于X不活跃的特异性 转录(XIST)，一种长的非编码RNA(LncRNA)。虽然这是XIST RNA唯一已知的功能， 它在拥有两条X染色体的个体的一生中继续被合成。一首非古典的 最近观察到XIST在细胞核外的B和T细胞亚群中的分布 健康的女性。这种非规范XIST表达式的机制和结果还没有 和其他几个有趣的观察结果表明，XIST具有可能 参与自身免疫性疾病的发病，独立于XCI，包括：1)XIST是一种 在易发生自身免疫的个体中存在高水平的lncRNA；2) 在SS、Ro/SSA和La/SSB中，主要靶向自身抗原是可以发现的RNA结合蛋白 和3)我们对XIST RNA序列的分析揭示了已知的 TLR7-刺激基序。同时，越来越多的证据表明，长期单独或在体内暴露于自我RNA 免疫复合体可以刺激致病的TLR7依赖的反应，这些观察支持我们的 假设XIST RNA通过作用于女性自身免疫易感性 内源性TLR7激动剂。我们建议以我们的初步数据为基础，系统地检查关键的 通过对人类生物标本和细胞模型的研究，这一假说的方方面面。在目标1中，高- 通过流式细胞术比较XIST的表达和分布模式 SS患者男性和女性外周血细胞中的RNA与性别匹配的健康对照组比较。 AIM 2将研究死亡细胞的XIST释放以及与SS自身抗原的潜在相互作用 确定XIST是否可以作为SS患者循环免疫复合体的一个组成部分。最后， 在目标3中，我们将评估XIST RNA作为TLR7配体的能力。这项工作有可能 明确XIST在SS发病机制中的新的促炎作用，这可能为未来提供信息 XIST治疗SS和HIST的研究进展 相关的自身免疫性疾病。

Project Summary/Abstract Sjögren’s syndrome (SS) is a systemic autoimmune disease that predominantly affects women, yet the mechanisms driving this strong gender bias are unknown. The X chromosome has been implicated in the increased female susceptibility to autoimmune diseases like SS, and compelling evidence suggests that abnormal X chromosome inactivation (XCI) may play a pathogenic role. XCI occurs during development to normalize X-linked gene dosage between men and women in a manner dependent on the X-inactive specific transcript (XIST), a long non-coding RNA (lncRNA). Although this is the only known function of XIST RNA, it continues to be synthesized throughout life in individuals with two X chromosomes. A non-classical distribution of XIST outside of the nucleus has recently been observed in a subset of B and T cells from healthy women. The mechanisms and consequences of this non-canonical XIST expression have not been explored, and several additional intriguing observations suggest that XIST possesses properties that may contribute to the pathogenesis of autoimmune diseases, independently of XCI, including: 1) XIST is a lncRNA present at high levels in individuals predisposed to the development of autoimmunity; 2) the dominantly targeted autoantigens in SS, Ro/SSA and La/SSB, are RNA-binding proteins that can be found in complexes with self-RNA; and 3) our analysis of the XIST RNA sequence reveals the presence of a known TLR7-stimulatory motif. Together with growing evidence that chronic exposure to self-RNA alone or in immune complexes can stimulate pathogenic TLR7-dependent responses, these observations support our hypothesis that XIST RNA contributes to the female susceptibility to autoimmunity by acting as an endogenous TLR7 agonist. We propose to build on our preliminary data to systemically examine the critical aspects of this hypothesis through the study of human biospecimens and cellular models. In Aim 1, high- throughput flow cytometric methods will be used to compare the expression and distribution pattern of XIST RNA in the peripheral blood cells of men and women with SS compared to sex-matched healthy controls. Aim 2 will examine XIST release from dying cells and potential interactions with SS autoantigens, to determine whether XIST could be a component of circulating immune complexes in patients with SS. Finally, in Aim 3, we will evaluate the capacity of XIST RNA to act as a TLR7 ligand. This work has the potential to define a novel proinflammatory role for XIST in the pathogenesis of SS, which could inform the future development of therapies that disrupt the disease promoting capacity of XIST for the treatment of SS and related autoimmune conditions.