Investigating novel roles for nesprin-1 and the LINC complex in Dilated Cardiomyopathy.

Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): British Heart Foundation Cardiomyopathies are an important cause of heart failure and sudden cardiac death. Recent studies have demonstrated the importance of the "passive" mechanical components of cardiomyocytes (CMs) as new causes for dilated cardiomyopathy (DCM). Nesprin-1/-2 are highly expressed in skeletal and cardiac muscle and together with SUN (Sad1p/UNC84)-domain containing proteins form the LInker of Nucleoskeleton and Cytoskeleton (LINC) complex at the nuclear envelope (NE), which, in association with lamin A/C and emerin, mechanically couples the nucleus to the cytoskeleton. We have recently identified novel nesprin-1 mutants in  DCM patients, which cause LINC complex disruption, leading to defects in nuclear organisation and myogenesis in vitro. We aim to investigate mechanisms through which these mutations lead to DCM. Therefore, we have generated a nesprin-1 mutant R8253Q knock-in (KI) mouse line (equivalent to human SYNE1 R8272Q) as the first clinically relevant animal model. 2. R8272Q is in close proximity to the binding regions to microtubule (MT) associated proteins kinesin light chain-1/2 and Akap6 at the nuclear envelope, which is potentially in involved in MT organization. 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 LV dysfunction and a tendency of DCM. Immunofluorescence (IF) of isolated adult cardiomyocytes (ACM) from KI mice showed perinuclear MT localization was significantly reduced, KLC-1/2 and AKAP6 were mislocalized from the NE and altered nuclear positioning. Therefore, we propose to investigate novel roles of nesprin-1 and the LINC complex in cardiomyocyte mechanotransduction using this KI model to explore roles of  nesprin-1 in microtubule organization, nuclear positioning, and CM homeostasis, which will yield insights into signalling leading to DCM and heart failure as well as inform strategies for translational approaches. [ABSTRACT FROM AUTHOR]