一个多发性骨骺发育不良大家系的临床特点及致病基因分析

目的通过对一个5代疑似多发性骨骺发育不良(multiple epiphyseal dysplasia,MED)的大家系(患者17例)进行临床特征分析和致病基因的筛查,为遗传咨询和产前分子诊断提供实验依据。方法采集家系成员病史,一般体检、关节、髋部X线片资料;收集该家系外周血样,提取样本DNA,靶向基因高通量测序方法对先证者DNA临床全外显子进行测序,使用Next Gene软件对测序序列进行比对分析,并进一步利用Ingenuity软件对存在的突变进行功能注释,寻找先证者致病突变。针对可疑突变,PCR和Sanger测序对家系其他成员DNA样本进行验证。结果该家系共5代,现存家系成员38人,系谱分析符合常染色体显性遗传特征。家系共有患者17例,其临床表现为:幼时出现走路姿势异常,后出现髋关节及膝关节疼痛,X线有典型骨骺发育不良病理改变。高通量测序及数据分析后,筛选出先证者(Ⅳ-3)软骨低聚物基质蛋白(cartilage oligomeric matrix protein,COMP)基因c.1153G>A(p.Asp385Asn)错义杂合突变,该突变导致其编码蛋白的第385位天冬氨酸被天冬酰胺替代。先证者家系其他成员符合基因型与表型共分离。结论COMP基因c.1153G>A错义杂合突变是导致该MED家系患者发病的分子机制,该突变首次在大家系中被报道,进一步明确了COMP基因c.1153G>A突变的致病性,有利于家系患者的进一步的诊治,也为产前诊断提供了实验依据。

Clinical characteristics and pathogenic gene analysis in a large pedigree with multiple epiphyseal dysplasia

Objective To provide experimental evidence for genetic counseling and prenatal molecular diagnosis by analyzing the clinical characteristics and screening for pathogenic genes of a five-generation suspected multiple epiphyseal dysplasia(MED)family(17 patients).Methods The family members'medical history,general physical examination and hip joint X-ray examination were collected.Peripheral blood samples of the family members were collected and DNA were extracted from these samples.The exons of clinical genes from probands'DNA were sequenced by High throughput sequencing method.Next Gene software was used to compare and analyze the sequence and INGENUITY software was further used to annotate the mutations in order to find the pathogenic mutations in probands.The suspicious mutations were confirmed in pedigree members by PCR and Sanger sequencing.Results The family consisted of 5 generations and 38 members.Pedigree analysis was consistent with autosomal dominant inheritance.There were 17 patients in the family,and their clinical manifestations showed abnormal walking posture in childhood,pain in hip and knee joints,and typical pathological changes of epiphyseal dysplasia on X-ray.Cartilage oligomeric matrix protein(COMP)gene c.1153G>A(p.Asp385Asn)missense heterozygous mutation was screened in proband,which was genotypically and phenotypically segregated in the pedigree.Conclusion A missense mutation of the comp gene has been identified in a pedigree affected with MED which was the first reported in a big family.Our result is conducive to the further diagnosis and treatment and also provides a molecular basisfor the future prenatal diagnosis.