Intermediate filaments in the heart: The dynamic duo of desmin and lamins orchestrates mechanical force transmission

Case Report: Diverse cardiac and muscular phenotypes in DES c.1024A>G (p.Asn342Asp) variant: a case series with limb weakness as the initial presentation

We report three patients with bilateral lower limb weakness as the initial symptom. Case 1 presented at 37 years old with bilateral lower limb weakness. The condition gradually worsened, eventually leading to wheelchair dependence. He later sought medical attention for heart failure. Echocardiography showed diffuse left ventricular dysfunction, and the electrocardiogram revealed third-degree atrioventricular block. Case 2 developed bilateral lower limb weakness at 38 years old, with milder symptoms. The main cardiac manifestation was paroxysmal atrial fibrillation. Case 3 presented at 33 years old with lower limb weakness and myalgia, with significant involvement of all four limbs. The primary cardiac finding was left ventricular hypertrophy, and the electrocardiogram showed sinus pauses. Despite the differences in clinical presentations, all three patients were diagnosed with the same DES c.1024A>G (p.Asn342Asp) variant. We discuss the possible factors contributing to the phenotypic differences. Based on the uniqueness of this pathogenic variant site, we propose recommendations for the treatment and management of desminopathy.

Endothelial cytoskeleton in mechanotransduction and vascular diseases

The cytoskeleton is an important structural component that regulates various aspects of cell morphology, movement, and intracellular signaling. It plays a pivotal role in the cellular response to biomechanical stimuli, particularly in endothelial cells, which are critical for vascular homeostasis and the pathogenesis of cardiovascular diseases. Mechanical forces, such as shear and tension, activate intracellular signaling cascades that regulate transcription, translation, and cellular behaviors. Despite extensive research into cytoskeletal functions, the precise mechanisms by which the cytoskeleton transduces mechanical signals remain incompletely understood. This review focuses on the role of cytoskeletal components in membrane, cytoplasm, and nucleus in mechanotransduction, with an emphasis on their structure, mechanical and biological behaviors, dynamic interactions, and response to mechanical forces. The collaboration between membrane cytoskeleton, cytoplasmic cytoskeleton, and nucleoskeleton is indispensable for endothelial cells to respond to mechanical stimuli. Understanding their mechanoresponsive mechanisms is essential for advancing therapeutic strategies for cardiovascular diseases.

Pathophysiological mechanisms of cardiomyopathies induced by desmin gene variants located in the C-Terminus of segment 2B

Desmin, the most abundant intermediate filament in cardiomyocytes, plays a key role in maintaining cardiomyocyte structure by interconnecting intracellular organelles, and facilitating cardiomyocyte interactions with the extracellular matrix and neighboring cardiomyocytes. As a consequence, mutations in the desmin gene (DES) can lead to desminopathies, a group of diseases characterized by variable and often severe cardiomyopathies along with skeletal muscle disorders. The basic desmin intermediate filament structure is composed of four segments separated by linkers that further assemble into dimers, tetramers and eventually unit-length filaments that compact radially to give the final form of the filament. Each step in this process is critical for proper filament formation and allow specific interactions within the cell. Mutations within the desmin gene can disrupt filament formation, as seen by aggregate formation, and thus have severe cardiac and skeletal outcomes, depending on the locus of the mutation. The focus of this review is to outline the cardiac molecular consequences of mutations located in the C-terminal part of segment 2B. This region is crucial for ensuring proper desmin filament formation and is a known hotspot for mutations that significantly impact cardiac function.