Introduction Cardiomyopathies are an important cause of heart failure and sudden cardiac death. Emerging evidence demonstrated the importance of the mechanical properties of cardiomyocytes as new causes for dilated cardiomyopathy (DCM). Nesprins-1/2 are highly expressed in cardiac and skeletal muscle and together with SUN1/2, lamin A/C and emerin form the nuclear envelope (NE) LInker of Nucleoskeleton-and-Cytoskeleton (LINC) complex, that mechanically couples the nucleus to cytoskeletal networks. Our recent data showed nesprin-1 mutations in DCM patients cause increased NE fragility and compromise LINC complex function in vitro, leading to disruption of mechanical connections between the plasma membrane and the nucleus, and may potentially affect microtubules (MT), myofibrils and sarcoplasmic reticulum when cells are exposed to mechanical stress accompanying DCM and heart failure. We aim to investigate novel roles of nesprin-1 and the LINC complex in cardiomyocyte mechanotransduction via exploring roles of nesprin-1 in microtubule organisation, nuclear positioning and cardiomyocyte homeostasis.Methods and
Results We have generated the first clinically relevant nesprin-1 mutant knock-in (KI) mouse line. Preliminary mouse echocardiography data showed significantly reduced thickness of left ventricle (LV) posterior wall in diastole and reduced % ejection fraction in the KIs at 15 weeks after birth, suggesting left ventricular dysfunction and a tendency of DCM, which is consistent with Echo observations in DCM patients harboring the same mutation. Immunofluorescence showed elongated and reduced nuclear circularity, loss of nesprin-1 NE staining in KI hearts, and also reduced staining of Akap6 and KLC1/2 at the NE as well as reduced perinuclear MT intensity and abnormal nuclear positioning in KI cardiomyocytes compared to the WT. Furthermore, GST-pull down and immunoprecipitation showed nesprin-1 interaction with AKAP6 and KLC1/2 was disrupted in both C2C12 myoblasts and KI heart and muscle tissue.
Conclusion Our model suggests a novel role of nesprin-1, in particular nesprin 1a2 isoform, in MT organization, nuclear positioning and cardiomyocyte homeostasis, thus serving as a platform to investigate novel pathological mechanism of nesprin-1 mutations in DCM. This project has the potential to uncover a novel mechanism that causes cardiomyocyte dysfunction, contributing to the pathogenesis of NE-related cardiomyopathies, which may yield insights into signalling leading to heart failure, with potential to influence the strategies for translational approaches.
Conflict of Interest None
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