I型胶原突变相关成骨不全症修饰基因及其功能的研究

Osteogenesis imperfecta (OI) is a teratogenic inherited motor system disease. 90% of OI is caused by the mutation of type I collagen encoding genes (COL1A1 and COL1A2) with autosomal dominant inheritance. Variable expressivity and incomplete penetrance are significant features of collagen-related OI. Our previous studies investigated the causative mutations in more than 700 patients with OI and established the mutation spectrum of causative genes in Chinese OI population. We analyzed the correlations between genotype and phenotype, and found that different patients with the same mutation in the COL1A1/2 gene (even in same family) might have remarkable differences in phenotypic spectrum, disease severity and penetrance. Based on patients with significant differences in phenotype and penetrance in the same collagen-related OI family, the modification effects of relevant genes on expression of type I collagen were studied through the modifier genes related with the expression of COL1A1/2 that were screened by next generation sequencing (whole genome sequencing and transcriptome sequencing), and the interventional effects on gene expression studied via patients’ skin fibroblast cells and OI animal models. It is expected that the results of this study will play a critical role in the earlier clinical warning and drug-target exploration of OI patients.

成骨不全（osteogenesis imperfecta，OI）是一种致畸、自残的遗传性运动系统疾病。90%的OI由I型胶原基因（COL1A1和COL1A2）突变所致，呈常染色体显性遗传。表现度变异和外显率不完全是I型胶原基因突变相关OI的重要特征。我们前期对700多例OI患者进行致病突变研究，构建了中国人群OI的致病基因突变谱，并进行基因型与表现型相关性分析，发现具有相同COL1A1/2基因突变的不同患者(即使为同一家系成员)，存在表型谱、疾病严重程度和外显率的显著差异。本研究以I型胶原变异致病的，具有相同致病突变、存在显著表型和外显率差异的OI家系为切入点，利用全基因组和转录子组测序技术筛选与COL1A1/2表达相关的修饰基因，并通过患者皮肤成纤维细胞及OI动物模型的基因表达干预，鉴定相关基因对I型胶原基因表达的修饰作用。预期本研究成果对OI患者的临床预警和药物靶点探索具有重要作用。

成骨不全症（osteogenesis imperfecta, OI）是一种以骨量减少和反复骨折为主要特征的单基因骨病。约85%以上的OI患者由I型胶原（collagen type I, COL1）编码基因COL1A1和COL1A2变异直接导致，呈常染色体显性遗传。外显不全和表现度变异（不规则显性遗传）是COL1A1/2变异致病OI的重要遗传学特征，即具有相同致病基因型的不同个体（即使来自同一家系）发病与否，以及疾病表现谱和严重程度存在显著差异。不规则显性遗传增加了OI临床诊断和遗传咨询的难度，导致误诊、漏诊和预后不良。明确不规则显性的遗传基础对于开展OI等单基因病的精准诊疗具有重要意义。前期我们在中国人OI大样本研究中发现20%以上的OI家庭存在表现度差异，约4%的家系存在外显不全。.本研究以I型胶原变异致病的、存在显著表型差异或外显率差异的4个OI家系为切入点，进行“OI亲子对”（OI重型先证者与其存在相同COL1A1/2致病基因型但无明显OI表型的父亲或母亲）皮肤成纤维细胞的转录组和蛋白质组学分析，筛选并鉴定出与不规则显性遗传相关的修饰基因。转录组分析发现has-miRNA-145-5p在先证者组低表达，但has-miRNA-3138在先证者组高表达。蛋白质组分析发现SERF2与ITGA1蛋白在4个亲子对的先证者和无表型OI个体组间存在显著差异，SERF2在先证者组表达较高，ITGA1在先证者组则表达较低，且两种蛋白在生物功能上可能存在互作。研究提示上述两种micro-RNA和两种蛋白质可能是导致不规则显性遗传的修饰分子，该结果有待进一步在其他外显不全家系中证实。亲子对基因组学研究表明，WNT1和FKBP10变异等位基因可能与COL1A1/2变异等位基因互作，导致较严重的OI表现。此外，本研究基于OI家系致病变异COL1A2: c.982G>A(p.Gly328Ser)构建了OI大鼠模型，成功模拟人类OI的外显不全，克服了人类研究组织取材困难等瓶颈，为开展OI不规则显性遗传修饰基因和作用机制的系统研究奠定了基础。本项目研究成果对于建立OI精准诊断、预警体系和鉴定新的药物靶点具有重要指导意义和潜在应用价值。