一例埃利伟综合征胎儿EVC2基因致病变异分析

doi:10.12280/gjszjk.20230131

摘要/Abstract

摘要：

目的： ，联合多种测序技术分析1例埃利伟综合征（Ellis-van Creveld syndrome，EVC综合征）胎儿基因变异，为遗传咨询提供依据。方法： 孕24周时超声检查提示胎儿双手轴后六指、四肢长骨短、心脏畸形和主动脉弓缩窄等。采集胎儿羊水及父母抗凝全血，提取基因组DNA，通过高通量测序平台进行Trio全外显子组测序（Trio-whole exome sequencing，Trio-WES）及低深度全基因组拷贝数变异测序（copy number variation sequencing，CNV-seq），利用Sanger测序及实时定量聚合酶链反应对疑似致病变异进行验证。结果： Trio-WES测序结果显示胎儿EVC2基因发生复合杂合变异：c.682G>C(p.A228P)纯合变异和loss1(Exon:2-22)all杂合缺失，经验证两个变异分别来源于其父母。根据美国医学遗传学与基因组学学会（American College of Medical Genetics and Genomics，ACMG）指南判定：c.682G>C(p.A228P)和loss1(Exon：2-22)all均为可能致病性变异，评分依据分别为PM1+PM2_Supporting+PM3+PP4和PVS1+PM2_Supporting。该胎儿确诊为EVC综合征，经遗传咨询后孕妇选择终止妊娠。结论： EVC2基因的c.682G>C(p.A228P)和loss1(Exon：2-22)all复合杂合变异可能是该EVC综合征胎儿的致病原因，上述两种变异均为新发变异，扩充了EVC2基因的突变谱，同时为该病的产前遗传咨询提供了理论依据。

关键词: Ellis-van Creveld综合征, 全外显子组测序, 遗传咨询, 突变, EVC2基因

Abstract:

Objective: The combined sequencing techniques were used in a case of Ellis-van Creveld syndrome (EVC syndrome) to test the genetic variants, so as to provide a basis for genetic consulting. Methods: Ultrasound examination of a fetus at 24 weeks of gestation showed the fetal six fingers behind hands′ axis, short limb of long bone, heart malformation, aortic arch constriction and other malformations. The amniotic fluid and parental peripheral bloods were collected and genomic DNAs were extracted. The high-throughput sequencing platform was used to perform Trio-whole exome sequencing (Trio-WES) and low-depth whole genome copy number variation sequencing (CNV-seq). Positive variants were verified by Sanger sequencing and real-time quantitative polymerase chain reaction. Results: The Trio-WES showed that there were compound heterozygous variants of EVC2 gene in fetus: c.682G>C(p.A228P) homozygous variation and loss1(Exon:2-22)all heterozygous loss. Two EVC2 gene variants were inherited from parents. According to the American College of Medical Genetics and Genomics (ACMG): c.682G>C(p.A228P) and loss1(Exon:2-22)all caused likely pathogenic variations: PM1+PM2_Supporting+PM3+PP4 and PVS1+PM2_Supporting. Conclusions: The compound heterozygous c.682G>C(p.A228P) and loss1(Exon:2-22)all variants of the EVC2 gene probably underlay the EVC syndrome in this fetus. Above two variations were new mutations, which enriched the mutational spectrum of the EVC2 gene. At the same time, it provided the theoretical basis for the prenatal genetic consultation.

Key words: Ellis-van Creveld syndrome, Whole exome sequencing, Genetic counseling, Mutation, EVC2 gene

吴琴, 冯暄, 周秉博, 田芯瑗, 郝胜菊, 惠玲, 陈雪. 一例埃利伟综合征胎儿EVC2基因致病变异分析[J]. 国际生殖健康/计划生育杂志, 2023, 42(5): 366-370.

WU Qin, FENG Xuan, ZHOU Bing-bo, TIAN Xin-yuan, HAO Sheng-ju, HUI Ling, CHEN Xue. Analysis of Pathogenic Variant of EVC2 Gene in A Fetus with Ellis-Van Creveld Syndrome[J]. Journal of International Reproductive Health/Family Planning, 2023, 42(5): 366-370.

图/表 3

图1 胎儿产前超声图注：A 胎儿胸腔明显缩窄，矢状面胸腹移行处可见明显切迹。B、C、D 胎儿长骨均明显粗大、短小、略屈曲。E、F 胎儿双手呈“握拳状”，双侧小指外侧另见一骨性回声。G 胎儿左心发育不良，左心室明显减小。H 胎儿主动脉弓缩窄、永存左上腔。

图2 胎儿CNV-seq检测结果及其父母EVC2基因变异分析注：A CNV-seq检测结果。B c.682G>C(p.A228P) Sanger测序结果。C loss1(Exon:2-22)all杂合缺失qPCR结果，纵坐标比值指外显子相对表达量，正常参考范围为0.8~1.2，高于1.2为重复，低于0.8为缺失。

图3 蛋白结构预测分析结果注：A 野生型。B 突变型。c.682G>C(p.A228P)变异减少了一个氢键，第228位氨基酸由丙氨酸（Ala）变为脯氨酸（Pro）。ASN 天冬酰胺，N 氮原子，C 碳原子。

参考文献 12

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