Genetic testing and prenatal diagnosis for two Chinese pedigrees affected with Alport syndrome due to variants ofCOL4A5 gene
马骞 1车凌仪 1孔祥东 1鞠翠钰
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作者信息
1. 郑州大学第一附属医院遗传与产前诊断中心，郑州 450052
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摘要
目的 对2个X连锁显性遗传Alport综合征(AS)家系进行COL4A5基因变异分析与产前诊断。 方法 选取2018年9月和2020年1月就诊于郑州大学第一附属医院产前诊断中心的2个无亲缘关系的汉族AS家系为研究对象。采集2个家系的临床资料，抽取家系各成员外周静脉血样及胎儿羊水样品，联合采用高通量测序(NGS)与PCR-Sanger测序法对家系成员与胎儿的COL4A5基因进行检测，并对候选变异进行致病性分析。通过PCR扩增SRY基因确定胎儿的性别。 结果 基因检测结果显示家系1中的先证者及胎儿均携带COL4A5基因第32外显子c.2723G>A(p.Gly908Glu)变异；家系2中的先证者及胎儿2均携带COL4A5基因第44外显子c.3817G>A(p.Gly1273Asp)变异。根据美国医学与遗传学学会(ACMG)相关指南，COL4A5基因c.2723G>A(p.Gly908Glu)和c.3817G>A(p.Gly1273Asp)变异均被判定为疑似致病性变异(PP2+PM2_Supporting)。在排除母体污染的情况下，PCR扩增SRY基因显示两个胎儿均为男性。 结论 COL4A5基因c.2723G>A(p.Gly908Glu)和c.3817G>A(p.Gly1273Asp)变异可能分别为这2个AS家系的遗传学病因。在产前诊断中，PCR扩增SRY基因能够快速鉴定胎儿性别，有利于筛查与分析。该变异的发现丰富了COL4A5基因的变异谱，为探索AS基因型-临床表型相关性提供参考。 Objective To analysis variants of COL4A5 gene in two Chinese pedigrees affected with Alport syndrome (AS) and provide prenatal diagnosis for them. Methods Two unrelated ethnic Han Chinese pedigrees who had visited the First Affiliated Hospital of Zhengzhou University respectively in September 2018 and January 2020 were selected as the study subjects. Clinical data were collected, and genomic DNA was extracted from peripheral venous blood and amniotic fluid samples for genetic testing. Following next generation sequencing, candidate variants of the COL4A5 gene were verified by Sanger sequencing and bioinformatic analysis. The gender of the fetuses was determined by the presence of sex-determining region on Y (SRY). Results Genetic testing revealed that the proband and a fetus from pedigree 1 had both harbored a c. 2723G>A (p.Gly908Glu) variant in exon 32 of theCOL4A5 gene, whilst the proband and a fetus from pedigree 2 had both harbored a c. 3817G>A (p.Gly1273Asp) variant in exon 44 of theCOL4A5 gene. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), both variants were classified as likely pathogenic (PP2+ PM2_Supporting). Following exclusion of maternal contamination, PCR amplification of the SRY region indicated that both fetuses were males. Conclusion The c. 2723G>A (p.Gly908Glu) and c. 3817G>A (p.Gly1273Asp) variants of theCOL4A5 gene probably underlay the AS in the two pedigrees. Detection of the SRY region can reliably identify the fetal sex, which is conducive to the prenatal diagnosis. Above results have also enriched the mutational spectrum of the COL4A5 gene and provided a reference for correlating the genotype and phenotype of the AS.
Abstract
Objective To analysis variants of COL4A5 gene in two Chinese pedigrees affected with Alport syndrome (AS) and provide prenatal diagnosis for them. Methods Two unrelated ethnic Han Chinese pedigrees who had visited the First Affiliated Hospital of Zhengzhou University respectively in September 2018 and January 2020 were selected as the study subjects. Clinical data were collected, and genomic DNA was extracted from peripheral venous blood and amniotic fluid samples for genetic testing. Following next generation sequencing, candidate variants of the COL4A5 gene were verified by Sanger sequencing and bioinformatic analysis. The gender of the fetuses was determined by the presence of sex-determining region on Y (SRY). Results Genetic testing revealed that the proband and a fetus from pedigree 1 had both harbored a c. 2723G>A (p.Gly908Glu) variant in exon 32 of theCOL4A5 gene, whilst the proband and a fetus from pedigree 2 had both harbored a c. 3817G>A (p.Gly1273Asp) variant in exon 44 of theCOL4A5 gene. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), both variants were classified as likely pathogenic (PP2+ PM2_Supporting). Following exclusion of maternal contamination, PCR amplification of the SRY region indicated that both fetuses were males. Conclusion The c. 2723G>A (p.Gly908Glu) and c. 3817G>A (p.Gly1273Asp) variants of theCOL4A5 gene probably underlay the AS in the two pedigrees. Detection of the SRY region can reliably identify the fetal sex, which is conducive to the prenatal diagnosis. Above results have also enriched the mutational spectrum of the COL4A5 gene and provided a reference for correlating the genotype and phenotype of the AS.
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