Theis Jeanne L, Zimmermann Michael T, Larsen Brandon T, Rybakova Inna N, Long Pamela A, Evans Jared M, Middha Sumit, de Andrade Mariza, Moss Richard L, Wieben Eric D, Michels Virginia V, Olson Timothy M
Cardiovascular Genetics Research Laboratory.
Division of Biomedical Statistics and Informatics, Department of Health Sciences Research.
Hum Mol Genet. 2014 Nov 1;23(21):5793-804. doi: 10.1093/hmg/ddu297. Epub 2014 Jun 11.
Locus mapping has uncovered diverse etiologies for familial atrial fibrillation (AF), dilated cardiomyopathy (DCM), and mixed cardiac phenotype syndromes, yet the molecular basis for these disorders remains idiopathic in most cases. Whole-exome sequencing (WES) provides a powerful new tool for familial disease gene discovery. Here, synergistic application of these genomic strategies identified the pathogenic mutation in a familial syndrome of atrial tachyarrhythmia, conduction system disease (CSD), and DCM vulnerability. Seven members of a three-generation family exhibited the variably expressed phenotype, three of whom manifested CSD and clinically significant arrhythmia in childhood. Genome-wide linkage analysis mapped two equally plausible loci to chromosomes 1p3 and 13q12. Variants from WES of two affected cousins were filtered for rare, predicted-deleterious, positional variants, revealing an unreported heterozygous missense mutation disrupting the highly conserved kinase domain in TNNI3K. The G526D substitution in troponin I interacting kinase, with the most deleterious SIFT and Polyphen2 scores possible, resulted in abnormal peptide aggregation in vitro and in silico docking models predicted altered yet energetically favorable wild-type mutant dimerization. Ventricular tissue from a mutation carrier displayed histopathological hallmarks of DCM and reduced TNNI3K protein staining with unique amorphous nuclear and sarcoplasmic inclusions. In conclusion, mutation of TNNI3K, encoding a heart-specific kinase previously shown to modulate cardiac conduction and myocardial function in mice, underlies a familial syndrome of electrical and myopathic heart disease. The identified substitution causes a TNNI3K aggregation defect and protein deficiency, implicating a dominant-negative loss of function disease mechanism.
基因定位研究已经揭示了家族性心房颤动（AF）、扩张型心肌病（DCM）以及混合性心脏表型综合征的多种病因，但在大多数情况下，这些疾病的分子基础仍不明。全外显子组测序（WES）为家族性疾病基因发现提供了一种强大的新工具。在此，这些基因组策略的协同应用确定了一种家族性综合征的致病突变，该综合征表现为房性快速心律失常、传导系统疾病（CSD）和DCM易感性。一个三代家族的七名成员表现出这种表达可变的表型，其中三名在儿童期出现CSD和具有临床意义的心律失常。全基因组连锁分析将两个同样可能的基因座定位到1p3和13q12染色体。对两名患病表亲的WES变异进行筛选，寻找罕见的、预测有害的、位于定位区域的变异，发现了一个未报告的杂合错义突变，该突变破坏了TNNI3K中高度保守的激酶结构域。肌钙蛋白I相互作用激酶中的G526D替代，具有可能的最有害的SIFT和Polyphen2评分，导致体外异常肽聚集，并且在计算机对接模型中预测野生型突变体二聚化改变但能量有利。来自一名突变携带者的心室组织显示出DCM的组织病理学特征，并且TNNI3K蛋白染色减少，伴有独特的无定形核内和肌浆内包涵体。总之，编码一种先前在小鼠中显示可调节心脏传导和心肌功能的心脏特异性激酶的TNNI3K突变，是一种电和心肌病性心脏病家族综合征的基础。所鉴定的替代导致TNNI3K聚集缺陷和蛋白质缺乏，提示功能丧失的显性负性疾病机制。
