Genomic profiling supports the diagnosis of primary ciliary dyskinesia and reveals novel candidate genes and genetic variants

Primary ciliary dyskinesia (PCD) is a rare inherited autosomal recessive or X-linked disorder that mainly affects lungs. Dysfunction of respiratory cilia causes symptoms such as chronic rhinosinusitis, coughing, rhinitis, conductive hearing loss and recurrent lung infections with bronchiectasis. It is now well known that pathogenic genetic changes lead to ciliary dysfunction. Here we report usage of clinical-exome based NGS approach in order to reveal underlying genetic causes in cohort of 21 patient with diagnosis of PCD. By detecting 18 (12 novel) potentially pathogenic genetic variants, we established the genetic cause of 11 (9 unrelated) patients. Genetic variants were detected in six PCD disease-causing genes, as well as in SPAG16 and SPAG17 genes, that were not detected in PCD patients so far, but were related to some symptoms of PCD. The most frequently mutated gene in our cohort was DNAH5 (27.77%). Identified variants were in homozygous, compound heterozygous and trans-heterozygous state. For detailed characterization of one novel homozygous genetic variant in DNAI1 gene (c. 947_948insG, p. Thr318TyrfsTer11), RT-qPCR and Western Blot analysis were performed. Molecular diagnostic approach applied in this study enables analysis of 29 PCD disease-causing and related genes. It resulted in mutation detection rate of 50% and enabled discovery of twelve novel mutations and pointed two possible novel PCD candidate genes.原发性纤毛运动障碍（Primary ciliary dyskinesia, PCD）是一种罕见的遗传性疾病，遗传方式主要为常染色体隐性或X连锁，病变主要累及肺部。呼吸道纤毛功能异常会引发慢性鼻-鼻窦炎、咳嗽、鼻炎、传导性耳聋以及伴支气管扩张的反复肺部感染等症状。目前学界已明确，致病性遗传变异会导致纤毛功能异常。本研究针对21例确诊为PCD的患者队列，采用基于临床外显子组的下一代测序（next-generation sequencing, NGS）技术以明确其潜在遗传病因。研究共检出18种（含12种新型）潜在致病性遗传变异，明确了11例（9例为无关个体）患者的遗传病因。上述遗传变异分别见于6种已知PCD致病基因，以及SPAG16、SPAG17基因——这两种基因此前未在PCD患者中被检出，但已被证实与PCD的部分临床症状相关。本队列中突变频率最高的基因为DNAH5（占比27.77%）。检出的变异存在纯合子、复合杂合子及反式杂合子三种状态。针对DNAI1基因中1种新型纯合子遗传变异（c. 947_948insG, p. Thr318TyrfsTer11），本研究开展了实时定量聚合酶链式反应（Real-time quantitative polymerase chain reaction, RT-qPCR）与蛋白质印迹（Western Blot）分析。本研究采用的分子诊断方法可同时检测29种PCD致病及相关基因，最终突变检出率达50%，成功发现12种新型突变，并提出2个潜在的新型PCD候选基因。