FLG基因高频突变K4671X与相关基因交互作用对皮肤屏障功能的影响

Skin barrier dysfunction is a key feature of atopic dermatitis (AD). Filaggrin is one of the important proteins in epidermis. Mutations in filaggrin gene (FLG) are found to be most strongly associated with AD genetically. Previous studies represent that one of the most common mutations, K4671X is specific in Chinese Han population. The mutation carriers in either AD or ichthyosis vulgaris is significantly more than that in normal controls. However, it is also illustrated that K4671X in heterozygous state cannot downregulate the expression of filaggrin per se. So we surmise that there exist other factors, for example, interation between FLG and other genes, impact skin barrier function cocurrently. TSLP and SPINK5 genes, both of which are known to be associated with filaggrin expression indirectly, will be sequenced in AD, ichthyosis vulgaris and normal controls with FLGwt/wt or FLGK4671X/wt. Statistic analysis will imply whether the interaction among them is associated with the development of AD or ichthyosis vulgaris. On the other hand, the expression of serine proteases and Th2 cytokines at both mRNA and protein levels in skin of patients and controls will be investigated to verify our speculation. The current project combines both genetic and immunological factors to investigate mechanism of skin barrier dysfunction in AD.

皮肤屏障功能缺陷是特应性皮炎的重要特征，中间丝相关蛋白是皮肤屏障的重要成分。编码该蛋白的基因中间丝相关蛋白基因是特应性皮炎的最强易感基因。前期研究发现，中国汉族人群特有的高频突变K4671X在特应性皮炎、寻常型鱼鳞病中的携带率显著高于正常人，但该杂合突变本身不能下调中间丝相关蛋白的表达。那么，是否在其他基因的共同作用下，携带K4671X杂合突变者易出现中间丝相关蛋白表达下降、进而影响皮肤屏障功能呢？本项目拟从与中间丝相关蛋白表达间接相关的丝氨酸蛋白酶抑制剂基因、人胸腺基质淋巴生成素基因入手，研究K4671X杂合突变是否与上述基因存在交互作用，主要分析K4671X杂合及野生型者在上述基因的基因型不同时，是否与特应性皮炎、鱼鳞病的发生相关，并从mRNA和蛋白水平进行验证丝氨酸蛋白酶、Th2炎症因子是否相应改变，将基因的交互作用及免疫因素结合研究特应性皮炎中皮肤屏障功能受损的机制。

本课题主要围绕“寻常鱼鳞病、特应性皮炎（AD）中基因型为FLGwt/K4671X的比例较正常人显著升高的原因”开展了基因学和功能学研究。从遗传学统计学和功能学研究发现，FLG基因尾部的K4671X突变与SPINK5、TSLP基因突变在AD发生中没有明显相互作用。进一步针对不同基因型患者开展随访，可能会有相关发现。后期对研究内容适当补充，探索了FLG基因多态性与特应性皮炎发病和临床的相关性、AD发病机制在家系中的表现规律、建立诊断标准提高AD诊断的敏感度、明确诊断一例易误诊为AD的SAM综合征，对AD的诊断与鉴别诊断、疾病发生规律和预后判断有一定意义。本研究已发表相关论文3篇（标注2篇），2篇有待发表；课题参与人获得课题相关省部级以上医学科技二等奖2项。