The Novel Desmin Mutant p.A120D Impairs Filament Formation, Prevents Intercalated Disk Localization, and Causes Sudden Cardiac Death

Abstract

T he intermediate filament (IF) protein desmin is encodedby the gene DES and contributes to the mechanical stabilization of the sarcomeres and cell contacts within the cardiac intercalated disk (ID). Desmin is the predominant IF protein of striated muscles. It belongs to the type III IF proteins characterized by a uniform assembly mechanism. In the first step of the in vitro assembly, 2 coiled-coil dimers form an antiparallel tetramer.1 These tetramers are the essential building blocks of the IF. Eight tetramers anneal in lateral orientation into unit length filaments. In the longitudinal elongation step, these unit length filaments are assembled and radially compacted into IF.2 Since the first reports on DES mutations, [3][4][5] it became obvious that DES mutations cause skeletal myopathies and different forms of cardiomyopathies. 6,7 Clinical Perspective on p 623In the meantime, >60 different DES mutations distributed over the whole sequence are known, which lead to filament formation defects with deposition of cytoplasmic desmin aggregates in the majority of cases. 8,9 However, the pathomechanisms of desmin aggregation leading to skeletal or cardiac myopathies are mechanistically not understood in detail. Moreover, 10-15 ARVC is an inherited cardiomyopathy clinically characterized by arrhythmias and predominately right ventricular dilatation leading to cardiac syncope, heart failure, or even sudden cardiac death (SCD). 16 It is well established that mutations in the genes coding for desmosomal plaque proteins cause ARVC [17][18][19] and rare forms of dilated cardiomyopathy. 20 In the cardiac muscle, desmin is found in costamers, the z-disk, and connected via plaque proteins to the cardiac desmosome within the ID. The molecular processes contributing to the destabilization of the ID through desmin filaments are fragmentarily understood. Especially, it is not known, how and which of the desmin mutations impair the connection of the IF system to the cardiac desmosome. Background-TheIn this study, we report a novel pathogenic DES mutation (c.359C>A, p.A120D), which seems to interfere particularly with the connection of desmin IF to the ID. Furthermore, we investigate whether the DES variants p.A120D and p.H326R (c.977A>G) affect the IF formation using ectopic expression cell culture systems and atomic force microscopy (AFM). These data reveal that desmin-p.A120D but not desmin-p. H326R inhibits the longitudinal assembly step, confirming its pathogenic potential. Materials and Methods Clinical Description of the PatientsIn family A, the 34-year-old female index patient (III:24) presented with atrial flutter, variable atrioventricular conduction ( Figure I in the online-only Data Supplement), and dilated atria. The average ventricular frequency was 64 bpm, and the atrial frequency was 120 bpm. In the ECG, some polymorphic premature ventricular contractions (PVCs) with a frequency of 45 to 111 bpm were detected ( Figure I in the online-only Data Supplement). The cardiological evaluation including 2-dimensional, M-m...

Mutations inFLNCare Associated with Familial Restrictive Cardiomyopathy

“…Because of the similar cellular effects of DES and FLNC mutations inducing cytotoxic protein aggregation, we investigated the localization of desmin in cardiac tissue of affected RCM patients. Desmin was absent at the intercalated discs in both patients, which was previously demonstrated for a RCM‐like patient carrying a DES mutation [Brodehl et al., ], but was not described for other DES mutations. The exact molecular link between filamin‐C and desmin at the cardiac intercalated disc is not known.…”

A Novel DES L115F Mutation Identified by Whole Exome Sequencing is Associated with Inherited Cardiac Conduction Disease

“…Second, the pathogenic mechanism underlying the association between the DES mutations and CCD remains unclear. Further studies are needed to investigate whether L115F can cause further changes in the subcellular localization and turnover of direct desmin-binding partners, subsequent cell apoptosis in the cardiac conduction system, or the loss of desmin-dependent gene regulatory function, as previously reported in some of DES missense mutations [11,12,25,26].…”

Higher order assembling of the mycobacterial essential polar growth factor DivIVA/Wag31

“…AFM provided a wealth of information on coiled-coil rich intermediate filaments (45)(46). To directly visualize the higher order forms of Wag31, AFM imaging of 2-7 days old tbWag31 samples were performed (table 1, figure 3).…”