Yang Shi-Wei, Chen Yan, Li Jun, Yin Jie, Qin Yu-Ming, Andelfinger Gregor, Wang Dao-Wu, Cao Ke-Jiang
Department of Cardiology, Nanjing Children's Hospital, Nanjing Medical University, Nanjing 210008, China.
Zhonghua Xin Xue Guan Bing Za Zhi. 2013 Apr;41(4):304-9.
Restrictive cardiomyopathy (RCM) is rare in children, and little is known about the molecular basis of RCM. The aim of this study was to investigate the clinical and myopathological characteristics and to detect mutations on cardiac sarcomere protein genes in three idiopathic pediatric RCMs.
Detailed clinical characteristics and familiar history were obtained in three idiopathic pediatric RCMs. One hundred healthy pediatric individuals were recruited as controls. Histological evaluation was performed with heart tissue retrieved at catheterization in case-1 and case-2. The entire coding sequences of four cardiac sarcomere protein genes, including cardiac troponin T (TNNT2), cardiac troponin I(TNNI3), β-myosin heavy chain (MYH7), and α-actin (ACTC)were screened for mutations. Sequence variants were then tested in the family as well as in 100 healthy control DNAs.
All three index cases were diagnosed as primary RCMs without family history, and their clinical conditions deteriorated rapidly. Case-1 was in combination with ventricular septal defect. Case-2 was in combination with mid- and inferoseptal hypertrophy. In case-1, myocardial biopsies displayed extensive an isomorphism and disarray of cardiomyocytes; electron microscopy showed large stacks of severely dysmorphic megamitochondria and focal Z-disc streaming. In case-2, endomyocardial biopsy revealed moderate myocyte hypertrophy with mild interstitial fibrosis; transmission electron microscopy showed misalignment of Z-bands and unequal Z-Z band distances. Genetic analysis identified two heterozygous missense mutations in TNNI3, with R204H in case-1 and R192H in case-3 respectively. A de novo heterozygous deletion in TNNT2 (p. Asn100_Glu101del) was identified in case-2. Sequence analysis shows that all three mutations are located in a position highly conserved across many species. The three mutations were negative for their parents and controls.
The clinical conditions in all three index cases are deteriorated rapidly after diagnosed as primary RCM. Three heterozygous mutations including two in TNNI3 and one in TNNT2 gene are identified in the three RCMs respectively, which are considered as causative mutations. These findings provide new insights into the molecular etiology responsible for pediatric RCM.
限制型心肌病（RCM）在儿童中较为罕见，其分子基础鲜为人知。本研究旨在调查3例特发性儿童RCM的临床和肌病理特征，并检测心脏肌节蛋白基因的突变情况。
获取3例特发性儿童RCM的详细临床特征和家族史。招募100名健康儿童作为对照。对病例1和病例2进行心导管检查时获取的心脏组织进行组织学评估。筛查4个心脏肌节蛋白基因的完整编码序列，包括心肌肌钙蛋白T（TNNT2）、心肌肌钙蛋白I（TNNI3）、β-肌球蛋白重链（MYH7）和α-肌动蛋白（ACTC）的突变情况。然后在家族成员以及100份健康对照DNA中检测序列变异。
所有3例索引病例均被诊断为无家族史的原发性RCM，其临床状况迅速恶化。病例1合并室间隔缺损。病例2合并中隔和下隔肥厚。病例1中，心肌活检显示心肌细胞广泛同型性和排列紊乱；电子显微镜显示大量严重畸形的巨型线粒体堆积以及局灶性Z线流。病例2中，心内膜活检显示心肌细胞中度肥大伴轻度间质纤维化；透射电子显微镜显示Z带排列不齐和Z-Z带间距不等。基因分析在TNNI3中鉴定出2个杂合错义突变，病例1为R204H，病例3为R192H。病例2中鉴定出TNNT2的一个新生杂合缺失（p.Asn100_Glu101del）。序列分析表明，所有3个突变均位于许多物种中高度保守的位置。这3个突变在其父母和对照中均为阴性。
所有3例索引病例在被诊断为原发性RCM后临床状况迅速恶化。在这3例RCM中分别鉴定出3个杂合突变，其中2个在TNNI3基因，1个在TNNT2基因，这些突变被认为是致病突变。这些发现为儿童RCM的分子病因学提供了新的见解。
