Best卵黄样黄斑营养不良及常染色体隐性卵黄样黄斑营养不良家系BEST1基因突变及临床表型分析

Analysis of BEST1 gene mutation and clinical phenotype in two families with Best vitelliform macular dystrophy and autosomal recessive bestrophinopathy

目的观察Best卵黄样黄斑营养不良(BVMD)及常染色体隐性卵黄样黄斑营养不良(ARB)家系BEST1基因突变类型及临床表型特征。方法回顾性临床研究。2019年11月至2021年3月于郑州大学第一附属医院眼科就诊的BVMD一家系(4例患者和6名家系成员)及ARB一家系(2例患者和2名家系成员),共计6例患者和8名正常家系成员纳入研究。详细询问其病史并行最佳矫正视力、眼底彩色照相、眼底自身荧光、眼电图及光相干断层扫描检查。采集患者及家系成员外周静脉血3 ml,提取全基因组DNA,应用基于靶向捕获的二代测序技术行基因测序,与数据库对比,筛选可疑致病突变位点,并对家系其他成员行Sanger验证。结果BVMD家系先证者临床表型为典型BVMD,其余患者临床表型为多灶性卵黄样黄斑营养不良。基因测序结果显示,4例患者及2名家系成员均携带BEST1基因第3号外显子c.240C>G(p.F80L)(M1)杂合错义突变,该变异为首次报道,定义为可疑致病突变。ARB家系先证者及另1例患者均为ARB。基因测序结果显示,2例患者均携带BEST1基因第5、2号外显子c.584C>T(p.A195V)(M2)、c.139C>A(p.R47S)(M3)2个杂合性错义突变,第3号外显子c.235dupT(p.S79Ffs*153)(M4)移码突变;为复合杂合突变。其中M2为已报道致病突变位点,M3致病性不明确,M4为首次报道。结论BEST1基因突变是导致BVMD及ARB的主要原因,不同突变位点可导致不同临床表型;BVMD及ARB具有遗传及临床表型异质性。

Objective To report the BEST1 gene mutations and clinical phenotypes in two pedigrees with Best vitelliform macular dystrophy(BVMD)and autosomal recessive bestrophinopathy(ARB).Methods A retrospective clinical study.From November 2019 to March 2021,in the Department of Ophthalmology of The First Affiliated Hospital of Zhengzhou University,the BVMD family(4 patients and 6 family members)and the ARB family(2 patients,2 family members),a total of 6 patients and 8 normal family members were included in the study.Detailed medical history was obtained;best corrected visual acuity,fundus color photography,electrophysiology,optical coherence tomography and fundus autofluorescence examination were performed.The clinical characteristics for all patients in the two families were analyzed.Three milliliter peripheral venous blood of all participants in the family was collected,and the whole genomic DNA was extracted with gene sequencing using next-generation sequencing technology based on targeted capture.Compared with the database to identify the pathogenicity mutation sites,suspected pathogenic mutation sites were selected,then mutations in other members in the family was assayed by Sanger sequencing.Results In family 1,the proband was demonstrated as typical BVMD,other patients were multifocal vitelliform macular dystrophy.The DNA sequencing result showed that all the 4 patients carried heterozygous missense mutations in exon 3 of BEST1 gene:c.240C>G(p.F80L)(M1)and 2 members carried this mutation,but without clinical phenotype.M1 was a likely-pathogenic mutation reported for the first time.In family 2,the proband and the other patient were diagnosed as ARB.The DNA result showed that the 2 patients carried heterozygous missense mutations in exon 5 and exon 2 of BEST1 gene:c.584C>T(p.A195V)(M2)、c.139C>A(p.R47S)(M3),and a heterozygous frameshift mutation in exon 3 of BEST1 gene:c.235dupT(p.S79Ffs*153)(M4).M2 was a pathogenic mutation reported previously.M3 variant was of undetermined significance.M4 was a first reported pathogenic mutation.Conclusions The BEST1 gene mutation is the main cause of BVMD and ARB.Different mutation sites have different clinical phenotypes.BVMD and ARB have genetic and clinical heterogeneity.