Gokhan Ilhan, Li Xia, Sendek Jack M, Mora Pagan Alex J, Akar Fadi G, Campbell Stuart G
Department of Biomedical Engineering, Yale University, New Haven, CT.
Department of Cellular and Molecular Physiology, Yale University, New Haven, CT.
bioRxiv. 2025 May 19:2025.05.15.654389. doi: 10.1101/2025.05.15.654389.
Mutations in , which encodes the protein desmoplakin, lead to cardiomyopathy with unusually high penetrance. Clinical features include ventricular tachyarrhythmias, fibro-fatty infiltration of both ventricles, and ultimately dilated cardiomyopathy. While some data have been gathered to explain the electrophysiological and contractile consequences of desmoplakin cardiomyopathy, a comprehensive mechanism linking mutations to ventricular dilation and heart failure remains elusive.
We use iPSC-derived engineered heart tissue (EHT) bearing a functional desmoplakin haploinsufficiency to model the heart failure phenotype that occurs in desmoplakin cardiomyopathy. Functional haploinsufficiency is secondary to a missense mutation, R451G, that results in proteolytic degradation of desmoplakin with no detectable protein. We complement functional data obtained in tissue-engineered constructs with cell biology assays in 2D cardiomyocytes to glean insights into the mechanism and mechanobiology of desmoplakin cardiomyopathy.
Engineered heart tissues harboring a desmoplakin insufficiency recapitulate a patient phenotype notable for hypocontractility and ventricular dilation. Surprisingly, DSP-mutant tissues exhibited a shortened resting sarcomere length that was dependent on protein kinase C activity. Concurrently, mechanical load on α-catenin was increased, suggesting a mechanism by which desmosomal insufficiency redistributes force to adherens junctions. Excessive loading on adherens junctions may act as a stimulus for avid insertion of series sarcomeres, shortening the length per sarcomere, and resulting in a contractile deficit. PKC inhibition rescues shortened sarcomere length in DSP-mutant tissues, suggesting that it could be a target for future molecular therapies.
Our study uncovers a novel mechanism underlying systolic dysfunction in desmoplakin cardiomyopathy. We not only recapitulate the disease phenotype, but we identify sarcomere length regulation through altered force transmission at the intercalated disc as a previously-unrecognized mechanism.
编码桥粒斑蛋白的基因突变会导致具有异常高外显率的心肌病。临床特征包括室性快速心律失常、双心室纤维脂肪浸润，最终发展为扩张型心肌病。虽然已经收集了一些数据来解释桥粒斑蛋白心肌病的电生理和收缩后果，但将基因突变与心室扩张和心力衰竭联系起来的全面机制仍然难以捉摸。
我们使用携带功能性桥粒斑蛋白单倍体不足的诱导多能干细胞衍生的工程心脏组织（EHT）来模拟桥粒斑蛋白心肌病中出现的心力衰竭表型。功能性单倍体不足继发于错义突变R451G，该突变导致桥粒斑蛋白的蛋白水解降解，且未检测到蛋白质。我们将在组织工程构建体中获得的功能数据与二维心肌细胞中的细胞生物学分析相结合，以深入了解桥粒斑蛋白心肌病的机制和力学生物学。
具有桥粒斑蛋白不足的工程心脏组织重现了以收缩功能减退和心室扩张为特征的患者表型。令人惊讶的是，DSP突变组织表现出缩短的静息肌节长度，这依赖于蛋白激酶C活性。同时，α连环蛋白上的机械负荷增加，这表明桥粒不足将力重新分配到黏附连接的一种机制。黏附连接上的过度负荷可能作为串联肌节大量插入的刺激因素，缩短每个肌节的长度，并导致收缩功能缺陷。PKC抑制可挽救DSP突变组织中缩短的肌节长度，这表明它可能是未来分子治疗的靶点。
我们的研究揭示了桥粒斑蛋白心肌病收缩功能障碍的一种新机制。我们不仅重现了疾病表型，而且还确定了通过改变闰盘处的力传递来调节肌节长度是一种以前未被认识的机制。
