目标区域捕获测序检测到一视网膜色素变性家系ABCA4基因新突变

Targeted next-generation sequencing identifies a novel ABCA4 gene mutation in a Chinese family with retinitis pigmentosa

目的研究我国一个常染色体隐性遗传的视网膜色素变性（RP）家系患者的临床表型及致病基因突变，并分析表型与基因型间的关系。方法实验研究。收集了宁夏人民医院眼科诊治的一个RP家系的临床资料，共有7名家庭成员参与研究，其中包括2名患者和5名正常成员。完善家系内所有参与成员的眼科检查，包括最佳矫正视力（BCVA）、视野、眼底照相、光学相干断层扫描（OCT）及全视野视网膜电流图（ERG）等。针对180个已知的遗传性视网膜疾病致病基因及9个高度可疑的候选基因设计目标区域捕获芯片，利用该捕获芯片对先证者（Ⅳ-4）进行目标区域内的高通量二代测序，借助优化的生物信息学分析对捕获的遗传变异进行筛查过滤，最终通过家系内共分离验证确认致病突变，进一步分析该突变与患者表型间的关系。结果临床检查结果表明该家系内的2名患者的临床表现均符合典型的RP改变，遗传学分析结果证实了ABCA4基因c．419G〉A突变是该家系的致病突变。该突变导致了ABCA4基因所编码的蛋白第140号氨基酸由精氨酸变为谷氨酰胺（p．Arg140Gln），保守性分析显示该突变位点在各物种中高度保守，PloyPhen-2软件预测结果表明该突变具有较高的致病性。结论本研究借助基于高通量二代测序平台的目标区域捕获测序，首次发现了ABCA4基因新突变p．Argl40Gln是一个常染色体隐性遗传RP家系的致病突变，进一步扩充了ABCA4基因的遗传突变谱及表型谱。

Objective To identify the pathogenic mutation in a Chinese family with autosomal recessive retinitis pigmentosa （RP） and to analyze its genotype-phenotype correlations. Methods Seven participants from one family were recruited for this experimental study, including 2 patients and 5 asymptomatic siblings. All participants underwent comprehensive ophthalmic examinations including best-corrected visual acuity, visual field testing, fundus photography, optical coherence tomography, and full-field flash electroretinography. Targeted next-generation sequencing （NGS） was selectively performed on the proband to reveal the RP causative mutation in this family using a microarray targeting 180 reported inherited retinal dystrophies （IRDs） causative genes and 9 potential IRDs relevant genes. All variants initially detected by NGS were then screened and filtered with optimized bioinformatics analyses and validated by intra-familial cosegregation analyses using Sanger sequencing. Genotype-phenotype correlation was also analyzed. Results Ophthalmic examination suggested the clinical diagnosis of typical RP for both patients from this family. Genetic analysis indicated ABCA4 c.419G〉A as the RP causative mutation for this family. This mutation induced the amino acid change from arginine to glutamine at residue 140 of the protein encoded by the ABCA4 gene （p.Arg140G1n）. Conservational analysis revealed the high conservation of the mutational spot among all tested species, and the online predictive software, PolyPhen-2, suggested the pathogenicity of this mutation. Conclusion By means of a targeted NGS approach, this study identifies a novel mutation, ABCA4 p.Arg140Gln, as the disease causative mutation for a Chinese autosomal recessive RP family, which extends both the genotypic and phenotypic spectrums for the ABCA4 gene.