Department of Biomedical Sciences, University of Pennsylvania School of Veterinary Medicine, Philadelphia, PA, USA; Division of Rheumatology, Department of Medicine, Hospital of the University of Pennsylvania, Philadelphia, PA, USA.
Department of Biomedical Sciences, University of Pennsylvania School of Veterinary Medicine, Philadelphia, PA, USA.
J Autoimmun. 2023 Sep;139:103084. doi: 10.1016/j.jaut.2023.103084. Epub 2023 Jul 1.
Systemic lupus erythematosus (SLE) is a highly female-biased systemic autoimmune disease, but the molecular basis for this female bias remains incompletely elucidated. B and T lymphocytes from patients with SLE and female-biased mouse models of SLE exhibit features of epigenetic dysregulation on the X chromosome which may contribute to this strong female bias. We therefore examined the fidelity of dynamic X-chromosome inactivation maintenance (dXCIm) in the pathogenesis of two murine models of spontaneous lupus-NZM2328 and MRL/lpr-with disparate levels of female-bias to determine whether impaired dXCIm contributes to the female bias of disease.
CD23 B cells and CD3 T cells were purified from age-matched C57BL/6 (B6), MRL/lpr, and NZM2328 male and female mice, activated in vitro, and processed for Xist RNA fluorescence in situ hybridization, H3K27me3 immunofluorescence imaging, qPCR, and RNA sequencing analyses.
The dynamic relocalization of Xist RNA and the canonical heterochromatin mark, H3K27me3, to the inactive X chromosome was preserved in CD23 B cells, but impaired in activated CD3 T cells from the MRL/lpr model (p < 0.01 vs. B6), and even more impaired in the heavily female-biased NZM2328 model (p < 0.001 vs. B6; p < 0.05 vs. MRL/lpr). RNAseq of activated T cells from NZM2328 mice revealed the female-biased upregulation of 32 X-linked genes distributed broadly across the X chromosome, many of which have roles in immune function. Many genes encoding Xist RNA-interacting proteins were also differentially expressed and predominantly downregulated, which may account for the observed mislocalization of Xist RNA to the inactive X chromosome.
Although evident in T cells from both the MRL/lpr and NZM2328 models of spontaneous SLE, impaired dXCIm is more severe in the heavily female-biased NZM2328 model. The aberrant X-linked gene dosage in female NZM2328 mice may contribute towards the development of female-biased immune responses in SLE-prone hosts. These findings provide important insights into the epigenetic mechanisms contributing to female-biased autoimmunity.
系统性红斑狼疮（SLE）是一种高度女性偏倚的系统性自身免疫性疾病，但这种女性偏倚的分子基础仍不完全清楚。SLE 患者和女性偏倚的 SLE 小鼠模型的 B 和 T 淋巴细胞表现出 X 染色体上表观遗传失调的特征，这可能导致这种强烈的女性偏倚。因此，我们研究了两种自发性狼疮小鼠模型-NZM2328 和 MRL/lpr-中动态 X 染色体失活维持（dXCIm）在发病机制中的保真度，以确定受损的 dXCIm 是否导致疾病的女性偏倚。
从年龄匹配的 C57BL/6（B6）、MRL/lpr 和 NZM2328 雄性和雌性小鼠中纯化 CD23 B 细胞和 CD3 T 细胞，在体外激活，并进行 Xist RNA 荧光原位杂交、H3K27me3 免疫荧光成像、qPCR 和 RNA 测序分析。
Xist RNA 和经典异染色质标记 H3K27me3 向失活 X 染色体的动态重定位在 CD23 B 细胞中得到保留，但在 MRL/lpr 模型的激活 CD3 T 细胞中受损（p < 0.01 与 B6 相比），在重度女性偏倚的 NZM2328 模型中甚至更严重受损（p < 0.001 与 B6 相比；p < 0.05 与 MRL/lpr 相比）。从 NZM2328 小鼠的激活 T 细胞的 RNAseq 显示，32 个 X 连锁基因在 X 染色体上广泛分布，呈女性偏倚上调，其中许多基因在免疫功能中发挥作用。编码 Xist RNA 相互作用蛋白的许多基因也表现出差异表达，主要下调，这可能解释了 Xist RNA 向失活 X 染色体的异常定位。
尽管在 MRL/lpr 和 NZM2328 自发性 SLE 模型的 T 细胞中都很明显，但在重度女性偏倚的 NZM2328 模型中，dXCIm 的受损更为严重。雌性 NZM2328 小鼠中异常的 X 连锁基因剂量可能有助于 SLE 易感宿主中女性偏倚的免疫反应的发展。这些发现为导致女性偏倚自身免疫的表观遗传机制提供了重要的见解。
