2例中国原发性纤毛运动障碍患者致病变异的鉴定

Identification of the pathogenic variants in two Chinese patients with primary ciliary dyskinesia

目的分析2例中国原发性纤毛运动障碍(PCD)患者的临床特征,并进行致病变异鉴定。方法收集患者的临床资料,采集患者外周血提取基因组DNA,应用全外显子组测序(WES)和Sanger测序鉴定PCD的潜在致病变异,最后通过生物信息学分析预测候选变异的致病性。结果2例中国PCD患者均有双肺弥漫性支气管扩张合并感染,鼻呼出一氧化氮(nNO)水平均低于正常值。WES结果发现两例患者均携带PCD已知致病基因的移码突变。患者1携带外动蛋白臂对接复合物亚基1(ODAD1)(NM_144577)基因纯合变异:c.702_705dupGCAG(p.P236Afs*11),患者2携带动力蛋白轴丝组装因子6(DNAAF6)(NM_173494)基因半合子变异:c.532_533delCT(p.L178Sfs*2)。2个变异均未被人类基因突变数据库(HGMD)收录。这两个移码突变均会引起开放阅读框改变,导致终止密码子提前出现。根据美国医学遗传学与基因组学学会(ACMG)指南,ODAD1基因c.702_705dupGCAG变异被判定为致病变异(PVS1+PM2+PM3+PP4),DNAAF6基因c.532_533delCT变异被判定为致病变异(PVS1+PM2+PM3+PP4)。结论本研究新发现的ODAD1变异c.702_705dupGCAG及DNAAF6变异c.532_533delCT分别是这2例患者的致病变异,支持其PCD诊断。以上结果将丰富ODAD1和DNAAF6的突变谱。

Objective To characterize the clinical features and to identify the pathogenic variants in two Chinese patients with primary ciliary dyskinesia(PCD).Methods The clinical data and peripheral blood sample from the patients were collected,and genomic DNA was subsequently extracted from the peripheral blood.Candidate pathogenic variants were identified using whole exome sequencing(WES)and further confirmed by Sanger sequencing technology.Finally,the pathogenicity of the variants was predicted through bioinformatic analysis.Results Two Chinese patients with PCD had diffuse bronchiectasis cpmlicated with recurrent infection and the decreased level of nasal nitric oxide(nNO).WES results showed that both patients carried frameshift mutations in known pathogenic genes of PCD.Patient 1 carried a homozygous variant in outer dynein arm docking complex subunit 1(ODAD1)(NM_144577):c.702_705dupGCAG(p.P236Afs*11)and patient 2 carried a hemizygous variant in dynein axonemal assembly factor 6(DNAAF6)(NM_173494):c.532_533delCT(p.L178Sfs*2).Neither variant had been recorded in The Human Gene Mutation Database(HGMD).Both frameshift variants caused changes in the open reading frame,which resulted in premature termination codon.According to the American College of Medical Genetics and Genomics(ACMG)guidelines,c.702_705dupGCAG in ODAD1 was categorized as a pathogenic variant(PVS1+PM2+PM3+PP4)and c.532_533delCT in DNAAF6 was categorized as a pathogenic variant(PVS1+PM2+PM3+PP4).Conclusions The novel variants c.702_705dupGCAG found in ODAD1 and c.532_533delCT found in DNAAF6 are pathogenic and support their PCD diagnosis for the two patients,respectively.These results may enrich the mutation spectrum of the ODAD1 and DNAAF6.