SOX9在VKH综合征黑色素脱失中的作用及分子机制研究

Vogt-Koyanagi-Harada (VKH) syndrome is a common blinding eye disease in China, and depigmentation is one of the most frequently seen clinical manifestations. However, the molecular mechanisms of depigmentation are still unknown. Our previous study showed that a SNP in SOX9 gene regulatory region was significantly associated with VKH syndrome, and the expression level of SOX9 gene and proportion of CD8+ T cell in VKH patients were significantly higher than those in healthy people. Other study identified that SOX9 was not only the vitiligo autoantigen in autoimmune polyendocrine syndrome type 1, but also could affected the proliferation and function of melanocytes. So it can be inferred that the SNP in SOX9 gene regulatory region may lead to increased gene expression level, then excess SOX9 protein may induce autoimmune attack against melanocytes and efficiently destruct them, and finally cause the depigmentation in VKH syndrome. In order to confirm this hypothesis, firstly, we take SOX9 gene as breakthrough point，then furtherly verify the correlation between SNP of SOX9 gene and VKH syndrome with larger samples, and reveal its role from susceptibility levels. Secondly, we explore the effects of SNP on gene transcription and translation function, elucidating the biological functions of the polymorphism. Finally, we investigate the contribution of SOX9 protein to autoimmune attack against melanocytes from both of the cell and animal levels, and reveal the molecular mechanisms of depigmentation, providing a new target for individual prevention and treatment of VKH syndrome.

Vogt-小柳原田(VKH)综合征是我国常见致盲眼病，黑色素脱失是此病的重要特征，但机制尚不清楚。我们前期实验发现SOX9基因调控区SNP与VKH综合征显著相关，且患者SOX9基因的表达量及CD8+T细胞比例显著高于正常人。文献报道SOX9蛋白既是白癜风的自身免疫抗原，又能影响黑色素细胞的增殖和功能。据此推测，SOX9基因调控区SNP导致基因表达量增加，进而诱发自身免疫攻击黑色素细胞，参与VKH综合征黑色素脱失的发生。为证实此假设，本研究以SOX9基因为切入点，用大样本进一步确定调控区SNP与VKH综合征的相关性，从易感层面揭示其作用；探究SNP对基因转录和蛋白翻译的调控作用，以阐明调控区SNP的生物学功能；从细胞水平和动物实验两方面探讨SOX9蛋白对自身免疫攻击黑色素细胞的调控作用，揭示SOX9通过何种机制参与VKH综合征黑色素脱失临床表现的发生，为VKH综合征个体化防治提供新的靶点。

Behçet病、VKH综合征和急性前葡萄膜炎是我国致盲率最高的葡萄膜炎类型。迄今为止，三种疾病发生的分子机制尚不完全清楚。本项目在中国汉族人群中鉴定Behçet病、VKH综合征和急性前葡萄膜炎的遗传易感基因，并探讨这些基因的遗传变异（单核苷酸多态性和拷贝数变异）影响疾病易感性的分子生物学机制，主要包括以下4个方面：1. 鉴定了miR-182/rs76481776多态与Behçet病和VKH综合征的遗传易感性显著相关，而与急性前葡萄膜炎的遗传易感性无显著相关；进一步研究发现，在CD3+CD28+抗体刺激的CD4+ T细胞水平，rs76481776的TT/CT基因型样本与CC基因型样本相比较，miR-182的表达水平显著升高；2. 鉴定了FoxO1基因与急性前葡萄膜炎伴发强直性脊柱炎的遗传易感性显著相关，而Behçet病和VKH综合征的遗传易感性无显著相关；3. 鉴定了FAS基因的拷贝数增加与Behçet病和VKH综合征的易感性显著相关；进一步研究发现，在CD3+CD28+抗体刺激的CD4+ T细胞水平，FAS基因拷贝数增加（>2）的样本与正常FAS基因拷贝数（=2）样本相比较，FAS的表达水平显著升高；同时，研究还进一步证实，活动期未用药的BD和VKH综合征患者中FAS基因的表达显著高于正常对照；4. 鉴定了ERAP1基因rs1065407和rs10050860单核苷酸多态与Behçet病的遗传易感性显著相关。此外，本项目还发现肝X受体可以通过抑制Th1和Th17细胞反应来调节异常免疫应答。综上所述，这些研究为葡萄膜炎的防治提供了新的靶点。