成骨不全家系Ⅰ型胶原COL1A1基因一个新RNA剪接突变位点的发现

A novel RNA-splicing mutation in COL1A1 gene causing osteogenesis imperfecta typeⅠin a Chinese family

目的:成骨不全(OI)又称脆骨病,是一种少见的遗传性骨病,临床表现主要包括骨密度降低、骨脆病增加、蓝巩膜、牙本质发育不全等,发病率约为1∶10000报告1个成骨不全(OI)家系并检测Ⅰ型胶原基因(COL1A1和COL1A2)的突变位点。方法:家系患者均具有易骨折和蓝巩膜等特点,诊断为OI。提取外周血基因组DNA,对COL1A1和COL1A2基因的所有启动子、外显子以及外显子-内含子进行DNA测序。基因突变位点的杂合状态通过序列特异引物PCR(PCR-SSP)进行证实。结果:DNA测序显示,2例OI患者COL1A1基因内含子27的5′端RNA剪接位点发生突变(c.1875+1G>A,即IVS27+1G>A),该突变与OI临床诊断一致。而家系中9名正常成员和50名健康对照者均未检测到该剪接位点突变。c.1875+1G>A在文献及胶原基因突变数据库均未见,为OI患者COL1A1基因的新突变位点,PCR-SSP证实了内含子27的杂合性。结论:本研究在一OI中国家系发现了致病基因COL1A1新的RNA剪接位点突变(c.1875+1G>A),详细的分子及临床特征对认识OI患者遗传和表型异质性、进一步研究OI基因型-表型关系有作用。

Objective：Osteogenesis imperfecta （OI）, also known as brittle bone disease, is a rare heterogeneous group of inherited disorders characterized by low bone mass, increased bone fragility, blue sclera and dentinogenesis imperfecta, with an estimated incidence of 1 ： 10000 worldwide. To report a Chinese family with osteogenesis imperfecta （OI） and detect mutation in type Ⅰ collagen gene, COL1A1 and COL1A2. Methods：Two cases, both with abnormal fragility of the skeleton and blue sclera, were diagnosed as OI. Genomic DNA was extracted from blood samples and all promoters, exons and exon/intron boundaries of COL1A1 and COL1A2 genes were sequenced. Polymerase chain reaction sequence-specific primers （PCR-SSP） was used to confirm patients＇ heterozygous state. Results：Direct DNA sequencing analysis of COL1A1 gene revealed a splicing mutation （c. 1875 ＋ 1 G 〉 A, also as IVS 27 ＋ 1 G 〉 A） that converted the 5＇ end of intron 27 from GT to AT. This mutation was found in both 2 affected individuals but 9 unaffected relatives and the 50 controls were not observed, which was consistent with the clinical diagnosis. This mutation （ c. 1875 ＋ 1G 〉 A） appeared to be novel, which was neither reported in literatures nor registered in the Database of Collagen Mutations. The heterozygous states of patients＇ intron 27 were confirmed by PCR-SSP. Conclusion ： We identify a novel RNA-splicing mutation （ c. 1875 ＋ 1G 〉 A） in COL1A1 gene resulting in OI in a Chinese family. The detailed molecular and clinical features will be useful for extending the evidence for genetic and phenotypic heterogeneity in OI and exploring the phenotype-genotype correlations in OI.