一个致死性先天性挛缩综合征7型家系的 CNTNAP1基因变异分析

Analysis of CNTNAP1 gene variants in a Chinese pedigree affected with lethal congenital contracture syndrome type 7

目的确定1个3次妊娠均出现羊水过多、早产, 其中两例活产出生, 出生后表现为呼吸困难、四肢挛缩、早亡等的家系的病因。方法应用全外显子测序技术(whole exome sequencing, WES)对胎儿组织及父母外周血样进行检测。经生物信息学分析, 对疑似致病性位点进行Sanger测序验证。结果 WES检测到胎儿组织标本CNTNAP1基因存在c.3718C>T(p.Arg1240Ter)无义纯合变异, 父母双方均检测到该位点的杂合变异。该变异尚未见数据库收录, 依据美国医学遗传学与基因组学学会遗传变异分类标准与指南, 该变异被判断为致病性(PVS1+PM2+PP4)。结论 CNTNAP1基因c.3718C>T(p.Arg1240Ter)变异可能是该致死性先天性挛缩综合征7型(lethal congenital contracture syndrome type 7, LCCS7)家系的发病原因。致病性变异的检出可以为其临床诊断提供依据, 有助于该家系的遗传咨询和产前诊断。

Objective To explore the genetic basis for a couple who had developed polyhydramnios during three pregnancies and given birth to two liveborns featuring limb contracture,dyspnea and neonatal death.Methods Whole-exome sequencing(WES)was carried out on fetal tissue and peripheral blood samples from the couple.Suspected variants were verified by Sanger sequencing.Results.The fetus was found to harbor homozygous nonsense c.3718OT(p.Argl240Ter)variants of the CNTNAP1 gene,which were respectively inherited from its mother and father.The variant was unreported previously.According to the guidelines of the American College of Medical Genetics and Genomics,the variant was predicted to be pathogenic(PVS1+PM2+PP4).Conclusion The novel homozygous nonsense variants of the CNTNAP1 gene probably underlay the lethal congenital contracture syndrome type 7(LCCS7)in this pedigree.Above finding has enabled genetic counseling and prenatal diagnosis for the family.