Bollen Ilse A E, Schuldt Maike, Harakalova Magdalena, Vink Aryan, Asselbergs Folkert W, Pinto Jose R, Krüger Martina, Kuster Diederik W D, van der Velden Jolanda
Department of Physiology, Amsterdam Cardiovascular Sciences, VU University Medical Center, Amsterdam, the Netherlands.
Department of Cardiology, Division of Heart and Lungs, University of Utrecht, University Medical Center Utrecht, Utrecht, the Netherlands.
J Physiol. 2017 Jul 15;595(14):4677-4693. doi: 10.1113/JP274145. Epub 2017 Jun 1.
Mutations in genes encoding cardiac troponin I (TNNI3) and cardiac troponin T (TNNT2) caused altered troponin protein stoichiometry in patients with dilated cardiomyopathy. TNNI3 resulted in haploinsufficiency, increased Ca -sensitivity and reduced length-dependent activation. TNNT2 caused increased passive tension. A mutation in the gene encoding Lamin A/C (LMNA ) led to reduced maximal force development through secondary disease remodelling in patients suffering from dilated cardiomyopathy. Our study shows that different gene mutations induce dilated cardiomyopathy via diverse cellular pathways.
Dilated cardiomyopathy (DCM) can be caused by mutations in sarcomeric and non-sarcomeric genes. In this study we defined the pathogenic effects of three DCM-causing mutations: the sarcomeric mutations in genes encoding cardiac troponin I (TNNI3 ) and cardiac troponin T (TNNT2 ; also known as the p.K210del) and the non-sarcomeric gene mutation encoding lamin A/C (LMNA ). We assessed sarcomeric protein expression and phosphorylation and contractile behaviour in single membrane-permeabilized cardiomyocytes in human left ventricular heart tissue. Exchange with recombinant troponin complex was used to establish the direct pathogenic effects of the mutations in TNNI3 and TNNT2. The TNNI3 and TNNT2 mutation showed reduced expression of troponin I to 39% and 51%, troponin T to 64% and 53%, and troponin C to 73% and 97% of controls, respectively, and altered stoichiometry between the three cardiac troponin subunits. The TNNI3 showed pure haploinsufficiency, increased Ca -sensitivity and impaired length-dependent activation. The TNNT2 mutation showed a significant increase in passive tension that was not due to changes in titin isoform composition or phosphorylation. Exchange with wild-type troponin complex corrected troponin protein levels to 83% of controls in the TNNI3 sample. Moreover, upon exchange all functional deficits in the TNNI3 and TNNT2 samples were normalized to control values confirming the pathogenic effects of the troponin mutations. The LMNA mutation resulted in reduced maximal force development due to disease remodelling. Our study shows that different gene mutations induce DCM via diverse cellular pathways.
编码心肌肌钙蛋白I（TNNI3）和心肌肌钙蛋白T（TNNT2）的基因突变导致扩张型心肌病患者肌钙蛋白蛋白化学计量改变。TNNI3导致单倍剂量不足、钙敏感性增加和长度依赖性激活降低。TNNT2导致被动张力增加。编码核纤层蛋白A/C（LMNA）的基因突变导致扩张型心肌病患者通过继发性疾病重塑使最大力量发展降低。我们的研究表明，不同基因突变通过多种细胞途径诱发扩张型心肌病。
扩张型心肌病（DCM）可由肌节和非肌节基因的突变引起。在本研究中，我们确定了三种导致DCM的突变的致病作用：编码心肌肌钙蛋白I（TNNI3）和心肌肌钙蛋白T（TNNT2，也称为p.K210del）的基因中的肌节突变，以及编码核纤层蛋白A/C（LMNA）的非肌节基因突变。我们评估了人左心室心脏组织中单个膜通透心肌细胞中的肌节蛋白表达、磷酸化和收缩行为。与重组肌钙蛋白复合物交换用于确定TNNI3和TNNT2突变的直接致病作用。TNNI3和TNNT2突变分别显示肌钙蛋白I表达降低至对照的39%和51%，肌钙蛋白T降低至64%和53%，肌钙蛋白C降低至73%和97%，并且三种心肌肌钙蛋白亚基之间的化学计量改变。TNNI3表现为单纯的单倍剂量不足、钙敏感性增加和长度依赖性激活受损。TNNT2突变显示被动张力显著增加，这不是由于肌联蛋白异构体组成或磷酸化的变化。与野生型肌钙蛋白复合物交换将TNNI3样品中的肌钙蛋白蛋白水平校正至对照的83%。此外，交换后，TNNI3和TNNT2样品中的所有功能缺陷均恢复至对照值，证实了肌钙蛋白突变的致病作用。LMNA突变由于疾病重塑导致最大力量发展降低。我们的研究表明，不同基因突变通过多种细胞途径诱发DCM。
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