Immune pathology and bone marrow transplant in disorders of Mecp2 overexpression

描述(申请人提供)：MeCP2-复制/三倍体综合征是一种破坏性的神经发育障碍，主要影响男孩，由X染色体中包含编码MeCP2(甲基CpG结合蛋白2)基因的区域复制(或三倍)引起。MeCP2结合DNA上甲基化的CpG位点，并招募转录复合体来调节基因的表达。因为MeCP2调节多种基因，所以准确定位特定功能被证明是困难的也就不足为奇了。除了MeCP2重复综合征外，MeCP2功能丧失突变约占Rett综合征病例的96%，这是另一种通常见于女孩的破坏性神经发育障碍。由于在RETT和MeCP2重复综合征中都可以看到强大的神经学成分，长期以来，MeCP2一直被认为是神经元的主要重要因素。然而，最近的研究表明，其他细胞，如Rett综合征的星形胶质细胞和小胶质细胞，以及MeCP2重复综合征的T细胞，也发挥了重要作用。这一理解为超越直接神经元干预的治疗方式开辟了可能性，由于任何神经元本身的操纵都涉及复杂性和风险，这一直是一种有问题的方法。在这里，我们建议检验一种假设，即MeCP2的过度表达会导致适应性免疫缺陷，从而导致过度的病理性先天炎症，最终导致发病率和死亡率。在MeCP2Tg3小鼠身上的初步数据显示，随着疾病的进展，周围器官经历了与大体病理表现和免疫渗透相关的显著重量减轻。然而，免疫特权器官(大脑和睾丸)不会受到这些变化的影响。这表明外周破坏性免疫过程在MeCP2Tg3小鼠的病理中起到了作用。此外，MeCP2Tg3小鼠显著增加了流感感染的死亡率。在流感模型中，MeCP2Tg3小鼠表现出CD8+T细胞反应不足和过度的先天炎症，但没有明显的病毒清除缺陷；我们打算测试CD8+T细胞缺陷导致代偿性增加的先天反应的假设，这会导致病理学导致死亡增加。第一个目的是通过在体外和体内对抗原提呈和T细胞激活的评估来验证树突状细胞故障导致适应性免疫反应缺陷的假设。这项建议的第二个目标将检验这样一个假设，即CD8+T细胞反应不足通过过度的先天免疫反应导致MeCP2Tg3小鼠死亡率增加。这将通过体外评估CD8+T细胞功能和体内评估CD8+T细胞对流感的反应来验证。第三个目标是通过骨髓移植或抑制过度的先天炎症来减少MeCP2Tg3小鼠死于流感。最终，这项工作的结果可能会导致基于免疫的治疗策略，用于MeCP2重复综合征患者。

DESCRIPTION (provided by applicant): MeCP2-duplication/triplication syndrome is a devastating neurodevelopmental disorder mostly affecting boys and is caused by duplication (or triplication) of the region in the X-chromosome containing the gene encoding MeCP2 (methyl-CpG-binding protein 2). MeCP2 binds to methylated CpG sites on DNA and recruits transcription complexes to modulate gene expression. Because MeCP2 modulates a multitude of genes, it is not surprising that pinpointing specific functions has proven difficult. In additio to MeCP2-duplication syndrome, loss-of-function mutations in MeCP2 account for about 96% of Rett Syndrome cases, another devastating neurodevelopmental disorder that is typically seen in girls. Because of the strong neurologic component seen in both Rett and MeCP2-duplication syndromes, MeCP2 was long assumed to be primarily important for neurons. However, recent studies have shown that other cells, such as astrocytes and microglia in Rett syndrome, and T cells in MeCP2-duplication syndrome, also play a significant role. This understanding opens up the possibility for treatment modalities beyond direct neuronal intervention, which has been a problematic approach due to the complexity and risk involved in any manipulation of neurons themselves. Here, we propose to test the hypothesis that MeCP2 overexpression causes defects of adaptive immunity that lead to excessive, pathologic innate inflammation, ultimately contributing to morbidity and mortality. Preliminary data in MeCP2Tg3 mice, which overexpress MeCP2 at 3-5 fold normal levels, reveals that as disease progresses, peripheral organs undergo significant weight loss associated with gross pathologic appearance and immune infiltrates. However, immune-privileged organs (brain and testes) are protected from these changes. This suggests that a peripheral destructive immune process is contributing to pathology in MeCP2Tg3 mice. In addition, MeCP2Tg3 mice have significantly increased mortality from influenza infection. In an influenza model, MeCP2Tg3 mice exhibit a deficient CD8+ T cell response and excessive innate inflammation without an apparent defect in viral clearance; we intend to test the hypothesis that CD8+ T cell defects result in a compensatory increased innate response, which causes pathology leading to increased death. The first aim is to test the hypothesis that dendritic cell malfunction contributes to defects of the adaptive immune response using both in vitro and in vivo assessment of antigen presentation and T cell activation. The second aim in this proposal will test the hypothesis that a deficient CD8+ T cell response contributes to increased mortality in MeCP2Tg3 mice via an excessive innate immune response. This will be tested by in vitro assessment of CD8+ T cell function and in vivo assessment of CD8+ T cell response to influenza. The third aim is to ameliorate death from influenza in MeCP2Tg3 mice via either bone marrow transplant or suppression of the excessive innate inflammation. Ultimately, results obtained from this work may lead to immune-based treatment strategies for patients with MeCP2-duplication syndrome.