Defining the Role of Dynamic X Chromosome Inactivation in Age-Associated B Cells for Female-Biased Systemic Lupus Erythematosus

定义动态 X 染色体失活在年龄相关 B 细胞中对女性系统性红斑狼疮的作用

• 批准号: 10749337
• 负责人: Claudia Darnell Lovell
• 金额: $ 3.52万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-01 至 2026-06-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10749337
• 关键词: Age; Alleles; Antibodies; Autoantibodies; Autoimmune Diseases; Autoimmunity; B cell differentiation; B-Cell Activation; B-Lymphocyte Subsets; B-Lymphocytes; Biological Assay; Breeding; Cell Compartmentation; Cell physiology; Cells; Cellular biology; Characteristics; Chemicals; Complex; Data; Deposition; Development; Diagnosis; Disease; Dosage Compensation (Genetics); Endosomes; Epigenetic Process; Female; Gene Dosage; Gene Expression; Gene Silencing; Genes; Genetic; Genetic Transcription; Height; Histones; Human; Immune; Impairment; Individual; Injections; Klinefelter' s Syndrome; Laboratory Finding; Link; Lymphocyte; Maintenance; Mammals; Mediating; Modeling; Mus; Pathogenesis; Pathway interactions; Patients; Persons; Phenotype; Play; Population; Predisposition; Pristane; Production; Proliferating; RNA; Regulator Genes; Research Proposals; Role; Sex Bias; Signal Transduction; Somatic Cell; Stimulus; Systemic Lupus Erythematosus; TLR7 gene; Testing; Time; Untranslated RNA; Up-Regulation; Visualization; Woman; X Chromosome; X Inactivation; cell type; dosage; ds-DNA; experimental study; immunoregulation; improved; in vitro Assay; insight; member; men; mouse model; novel; recruit; response; risk variant; transcriptome sequencing

Project Summary / Abstract 90% of individuals diagnosed with systemic lupus erythematosus (SLE) are women, but the underlying mechanisms that govern sex bias in autoimmune disease are not understood. Susceptibility to SLE increases with the number of X chromosomes carried by an individual, and increased expression of X-linked genes has been found in women with SLE. These findings suggest that gene expression from two X chromosomes likely contributes to female-biased SLE pathogenesis. The dosage of X-linked gene expression in mammals with more than one X chromosome is balanced by epigenetically silencing one X chromosome through X-chromosome inactivation (XCI). XCI is maintained in somatic cells by association of repressive epigenetic features with the inactive X chromosome (Xi), including coating of the Xi with the long non-coding RNA Xist. Despite these repressive features, some genes have been shown to escape silencing from the Xi. Our lab discovered that B cells, a key cell type in SLE pathogenesis, have “dynamic” maintenance of XCI, where naïve B cells lack visible Xist RNA signal yet demonstrate re-localization of Xist RNA to the Xi upon activation. Dynamic XCI maintenance is disrupted and X-linked immune genes are aberrantly expressed in SLE B cells, suggesting that impaired localization of repressive epigenetic marks on the Xi may cause aberrant escape of immune genes from the Xi, enhancing B cell activity. “Age-associated B cells” (ABCs) are emerging as a critical cell type in female-biased autoimmunity and respond robustly to signaling through the TLR7 pathway. Several TLR7 pathway members are X-linked and have been identified as risk variants in SLE. To determine the importance of contributions from the X chromosome in female-biased SLE, I will define epigenetic features of the Xi in ABCs and elucidate the impact of perturbed XCI maintenance in the B cell compartment on SLE pathogenesis. In Aim 1, I hypothesize that ABCs have dynamic XCI maintenance, and that X-linked immune-regulatory genes escape silencing in ABCs. I will isolate murine splenic B cells and visualize the association of repressive epigenetic features with the Xi during differentiation and activation of ABCs and perform allele-specific RNA sequencing to determine genes that escape silencing in ABCs. In Aim 2, I will build on my preliminary data that demonstrates that female mice with a B cell-specific Xist deletion yielding perturbed XCI (“Xist cKO”) are more susceptible to spontaneous and chemically-induced SLE-like disease. I hypothesize that impaired XCI maintenance in female Xist cKO mice leads to upregulation of immune-regulatory X-linked genes, yielding B cells that differentiate more readily into effector populations and produce more antibodies upon stimulation. I will assay transcriptional and functional characteristics of B cells from female Xist cKO mice at steady state and during the development of spontaneous and chemically induced SLE. Investigating the epigenetic mechanisms of XCI maintenance in ABCs will reveal how genetic contributions from the Xi are critical for ABC function, and for the first time will illuminate an X chromosome-based mechanism that underlies female-biased autoimmunity.

项目概要/摘要 90% 被诊断患有系统性红斑狼疮 (SLE) 的人是女性，但潜在的 控制自身免疫性疾病性别偏见的机制尚不清楚。系统性红斑狼疮的易感性增加 随着个体携带的 X 染色体数量的增加，X 连锁基因的表达增加 已在患有 SLE 的女性中发现。这些发现表明，两条 X 染色体的基因表达可能 导致女性偏向的 SLE 发病机制。哺乳动物中X连锁基因表达的剂量 通过 X 染色体表观遗传沉默一条 X 染色体来平衡一条 X 染色体 失活（XCI）。 XCI 通过抑制表观遗传特征与 失活的 X 染色体 (Xi)，包括用长非编码 RNA Xist 涂覆的 Xi。尽管有这些 由于具有压制性特征，一些基因已被证明能够逃脱习近平的沉默。我们的实验室发现B 细胞是 SLE 发病机制中的关键细胞类型，具有 XCI 的“动态”维持，而幼稚 B 细胞缺乏可见的 XCI Xist RNA 信号还表明 Xist RNA 在激活后重新定位到 Xi。动态XCI维护 被破坏并且 X 连锁免疫基因在 SLE B 细胞中异常表达，表明受损的 Xi 上的抑制性表观遗传标记的定位可能会导致免疫基因从 Xi 异常逃逸， 增强B细胞活性。 “年龄相关 B 细胞”(ABC) 正在成为女性偏向的关键细胞类型 自身免疫并通过 TLR7 途径对信号传导做出强烈反应。几个 TLR7 通路成员 是 X 连锁的，并已被确定为 SLE 的风险变异。确定贡献的重要性 女性偏向性 SLE 中的 X 染色体，我将定义 ABC 中 Xi 的表观遗传特征并阐明 B 细胞室中 XCI 维持受到干扰对 SLE 发病机制的影响。在目标 1 中，我假设 ABC 具有动态 XCI 维持，并且 X 连锁免疫调节基因在 ABC。我将分离小鼠脾 B 细胞并可视化抑制性表观遗传特征与 Xi 在 ABC 分化和激活期间进行等位基因特异性 RNA 测序以确定基因 逃脱ABC中的沉默。在目标 2 中，我将根据初步数据证明雌性小鼠 具有 B 细胞特异性 Xist 缺失，产生扰动的 XCI（“Xi​​st cKO”）更容易自发和 化学诱发的 SLE 样疾病。我假设雌性 Xist cKO 小鼠的 XCI 维持受损 导致免疫调节 X 连锁基因上调，产生更容易分化为 效应群体并在刺激后产生更多抗体。我将检测转录和功能 雌性 Xist cKO 小鼠的 B 细胞在稳态和自发性发育过程中的特征 和化学诱导的 SLE。研究 ABC 中 XCI 维持的表观遗传机制将揭示 Xi 的遗传贡献如何对 ABC 功能至关重要，并将首次阐明 X 基于染色体的机制是女性偏向性自身免疫的基础。