Pan Yun, Wang Zha-Gen, Liu Xing-Yuan, Zhao Hong, Zhou Ning, Zheng Gui-Fen, Qiu Xing-Biao, Li Ruo-Gu, Yuan Fang, Shi Hong-Yu, Hou Xu-Min, Yang Yi-Qing
Department of Pediatrics, Tongji Hospital, Tongji University School of Medicine, Shanghai, 200065, China.
Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, 200030, China.
Pediatr Cardiol. 2015 Oct;36(7):1400-10. doi: 10.1007/s00246-015-1173-x. Epub 2015 Apr 10.
Congenital heart disease (CHD) is the most prevalent type of birth defect in humans and is the leading non-infectious cause of infant death worldwide. There is a growing body of evidence demonstrating that genetic defects play an important role in the pathogenesis of CHD. However, CHD is a genetically heterogeneous disease and the genetic basis underpinning CHD in an overwhelming majority of patients remains unclear. In this study, the coding exons and splice junction sites of the TBX1 gene, which encodes a T-box homeodomain transcription factor essential for proper cardiovascular morphogenesis, were sequenced in 230 unrelated children with CHD. The available family members of the index patient carrying an identified mutation and 200 unrelated ethnically matched healthy individuals used as controls were subsequently genotyped for TBX1. The functional effect of the TBX1 mutation was predicted by online program MutationTaster and characterized by using a dual-luciferase reporter assay system. As a result, a novel heterozygous TBX1 mutation, p.Q277X, was identified in an index patient with double outlet right ventricle (DORV) and ventricular septal defect (VSD). Genetic analysis of the proband's available relatives showed that the mutation co-segregated with CHD transmitted in an autosomal dominant pattern with complete penetrance. The nonsense mutation, which was absent in 400 control chromosomes, altered the amino acid that was completely conserved evolutionarily across species and was predicted to be disease-causing by MutationTaster. Biochemical analysis revealed that Q277X-mutant TBX1 lost transcriptional activating function when compared with its wild-type counterpart. This study firstly associates TBX1 loss-of-function mutation with enhanced susceptibility to DORV and VSD in humans, which provides novel insight into the molecular mechanism underlying CHD and suggests potential implications for the development of new preventive and therapeutic strategies for CHD.
先天性心脏病（CHD）是人类中最常见的出生缺陷类型，也是全球婴儿死亡的主要非传染性原因。越来越多的证据表明，基因缺陷在CHD的发病机制中起重要作用。然而，CHD是一种基因异质性疾病，绝大多数患者CHD的遗传基础仍不清楚。在本研究中，对230名无亲缘关系的CHD患儿的TBX1基因编码外显子和剪接连接位点进行了测序，该基因编码一种对正常心血管形态发生至关重要的T盒同源域转录因子。随后，对携带已鉴定突变的索引患者的可用家庭成员以及200名无亲缘关系、种族匹配的健康个体作为对照进行了TBX1基因分型。通过在线程序MutationTaster预测TBX1突变的功能效应，并使用双荧光素酶报告基因检测系统进行表征。结果，在一名患有右心室双出口（DORV）和室间隔缺损（VSD）的索引患者中鉴定出一种新的杂合TBX1突变，p.Q277X。对先证者可用亲属的基因分析表明，该突变与以完全显性的常染色体显性模式遗传的CHD共分离。在400条对照染色体中不存在的无义突变改变了在物种间进化上完全保守的氨基酸，并被MutationTaster预测为致病突变。生化分析表明，与野生型相比，Q277X突变型TBX1失去了转录激活功能。本研究首次将TBX1功能丧失突变与人类对DORV和VSD的易感性增加联系起来，这为CHD的分子机制提供了新的见解，并为CHD新的预防和治疗策略的开发提供了潜在的启示。
