Novel nesprin-1 mutations associated with dilated cardiomyopathy cause nuclear envelope disruption and defects in myogenesis

Abstract

Nesprins-1 and -2 are highly expressed in skeletal and cardiac muscle and together with SUN (Sad1p/UNC84)-domain containing proteins and lamin A/C form the LInker of Nucleoskeleton-and-Cytoskeleton (LINC) bridging complex at the nuclear envelope (NE). Mutations in nesprin-1/2 have previously been found in patients with autosomal dominant Emery–Dreifuss muscular dystrophy (EDMD) as well as dilated cardiomyopathy (DCM). In this study, three novel rare variants (R8272Q, S8381C and N8406K) in the C-terminus of the SYNE1 gene (nesprin-1) were identified in seven DCM patients by mutation screening. Expression of these mutants caused nuclear morphology defects and reduced lamin A/C and SUN2 staining at the NE. GST pull-down indicated that nesprin-1/lamin/SUN interactions were disrupted. Nesprin-1 mutations were also associated with augmented activation of the ERK pathway in vitro and in hearts in vivo. During C2C12 muscle cell differentiation, nesprin-1 levels are increased concomitantly with kinesin light chain (KLC-1/2) and immunoprecipitation and GST pull-down showed that these proteins interacted via a recently identified LEWD domain in the C-terminus of nesprin-1. Expression of nesprin-1 mutants in C2C12 cells caused defects in myoblast differentiation and fusion associated with dysregulation of myogenic transcription factors and disruption of the nesprin-1 and KLC-1/2 interaction at the outer nuclear membrane. Expression of nesprin-1α2 WT and mutants in zebrafish embryos caused heart developmental defects that varied in severity. These findings support a role for nesprin-1 in myogenesis and muscle disease, and uncover a novel mechanism whereby disruption of the LINC complex may contribute to the pathogenesis of DCM.

Emery‐Dreifuss muscular dystrophy

“…Such proteins include emerin, LMNA, nesprin‐1, nesprin‐2, LUMA, SUN1, and SUN2, which are encoded by the EMD , LMNA , SYNE1 , SYNE2 , TMEM43 , SUN1 , and SUN2 genes, respectively . Specifically, the linker of nucleoskeleton‐and‐cytoskeleton (LINC) bridging complex located at the nuclear envelope is believed to tether the nucleo and cyto‐skeletons, and is composed of emerin, LMNA, nesprin‐1 and nesprin‐2, SUN1 and SUN2 . An exception is FHL1, a protein encoded by the gene of the same name, which localizes to the sarcomere and the sarcolemma; at the former, it contributes to sarcomere assembly …”

“…17,18,[20][21][22][23]43,[52][53][54][55][56][57][58][59][60][61][62][63][64][65][66] Specifically, the linker of nucleoskeleton-and-cytoskeleton (LINC) bridging complex located at the nuclear envelope is believed to tether the nucleo and cyto-skeletons, and is composed of emerin, LMNA, nesprin-1 and nesprin-2, SUN1 and SUN2. 35,67 An exception is FHL1, a protein encoded by the gene of the same name, which localizes to the sarcomere and the sarcolemma; at the former, it contributes to sarcomere assembly. 38,39 Mutant forms of emerin show diminished transport to the inner nuclear membrane, 68 and have been associated with decreased nuclear invagination and abnormalities in nuclear Ca ++ transients.…”

Cardiolaminopathies from bench to bedside: challenges in clinical decision-making with focus on arrhythmia-related outcomes

“…In this context, elevated TGFbeta 2 and Akt/mTOR activation could also be the cause of reduced lamin A and prelamin A levels [15,17] at the cardiomyocyte nuclear envelope, a condition that favors LINC disorganization [12]. In agreement with this pathogenetic hypothesis, Erk 1/2 activation has been demonstrated in the presence of pathogenetic LMNA and SYNE1 mutations [7,13], and altered positioning of muscle nuclei has been demonstrated in LMNA, SYNE1 and SUN1 -linked Emery-Dreifuss muscular dystrophy with cardiomyopathy [12–14,18]. …”

“…The connection with extranuclear signal transducers is ensured by the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex, a protein chain including integral proteins of the inner and outer nuclear membrane, such as SUN1/2 and nesprin1/2 (encoded by SYNE1/2 genes), attached to lamins on the nuclear side and to actin and other cytoskeleton constituents on the cytoplasmic side. LINC proteins are reduced [12,13] or even mutated [13,14] in patients affected by cardiolaminopathies. The proven effect of LINC disorganization and reduced interplay between LINC components and lamins in laminopathic muscle cells is defective myonuclear positioning [12,14], which is a cause of altered muscle cell functionality [14].…”

Semantic Segmentation of HeLa Cells: An Objective Comparison between one Traditional Algorithm and Three Deep-Learning Architectures

“…The nuclear envelope (NE) is a bi-layer membrane that separates the nucleus with the chromosomes from the rest of the cellular compartments [10] and contains a large number of membrane proteins with sophisticated roles and functions [11][12][13][14]. The structure and condition of the NE is of huge importance as it has been related to viral infections [15][16][17][18][19], Muscular dystrophy [20], Cancer [21][22][23][24][25], Osteoporosis [26], Cardiovascular diseases [27][28][29], other diseases [30][31][32], and ageing [33][34][35]. Therefore, algorithms for the segmentation, visualisation and analysis of the NE could provide parameters to understand the conditions of health and disease of a cell.…”