FLNB基因第35号外显子突变在青少年特发性脊柱侧凸中的作用机制研究

Adolescent idiopathic scoliosisis a complex developmental syndrome and its etiology remains enigmatic. The prognosis of AIS patients varies with the degree of the curve at first present and gender. Genetic studies have revealed that multiple susceptibility loci contribute to the disease risk, the degree of the curve and response to brace treatment, but their roles in the diagnosis and treatment are still limited. In a genome-wide rare variant burden analysis using exome sequencing data of 2 AIS families and 100 Chinese sporadic AIS cases, we identified 20 patients with rare variants in the exon 35 of FLNB gene. More importantly, FLNB variants were associated with worse response to brace treatment. Our pre-experiment results showed that FLNB variants accelerated chondrocyte maturation. This application planed to illustrate the clinical features of the AIS patients with FLNB mutations, and use FLNB mutant mice and immunoprecipitation to illustrate the influence of mutant FLNB gene on chondrocytes in particular. We intended to verify the downstream molecules and pathway involved withdysregulated chondrocyte differentiation，thus reveal a new clue for the diagnosis, prognosis and treatment of AIS.

青少年特发性脊柱侧凸（adolescent idiopathic scoliosis，AIS）的病因未明且不同患者的预后具有较大的异质性，以往的研究发现一些易感位点与疾病的发生、角度大小或支具治疗效果相关，但在AIS的诊断和治疗过程中作用仍有限。本课题组前期的全外显子组测序分析发现：2个AIS家系及20例汉族散发AIS患者（20/100）携带FLNB基因第35号外显子区内的罕见突变，且该类患者支具治疗有效率明显低于无突变患者。前期的预实验结果提示：FLNB基因突变能促进软骨细胞分化。本课题拟在整合患者临床信息的基础上分析基因突变的临床意义，采用FLNB基因点突变小鼠、免疫共沉淀等手段对FLNB基因第35号外显子突变引起的功能改变特别是对软骨细胞的功能影响进行重点探究，并阐明引起功能改变的下游效应分子和通路。为AIS的临床诊断、预后判断和治疗选择提供新思路。

青少年特发性脊柱侧凸（AIS）是最常见的脊柱畸形，其病因尚未明确。患者随访检查接受的辐射、高昂的手术费用、长期的疼痛或不适造成了巨大的社会负担。遗传学因素被认为在其发病中发挥了重要的作用。本课题前期与预实验结果提示：1）部分AIS 患者携带FLNB基因的罕见突变；2）FLNB基因突变能显著促进间充质干细胞的成软骨分化。在课题的执行过程中，首先通过扩大样本量进行全外显子测序分析确定了FLNB基因是AIS的一新发现的致病基因，接着使用单因素和多因素Cox回归分析发现患者的初次就诊角度大小和携带突变数量可能为影响角度进展的独立预后因素, 并使用计算机蛋白结构分析与同源模建、免疫共沉淀、细胞免疫荧光等实验对FLNB基因突变引起的功能改变和分子机制进行研究，结果提示AIS相关的基因突变可能通过影响其与TTC26的相互作用，影响应力纤维的生成，从而调控软骨细胞的分化。本项目的研究成果丰富了AIS的遗传学背景，为后续AIS的致病机制研究提供了新的方向。