The Desmin Mutation DES-c.735G>C Causes Severe Restrictive Cardiomyopathy by Inducing In-Frame Skipping of Exon-3.

Andreas Brodehl,Marcus-André Deutsch,Hendrik Milting,Sandra Ratnavadivel,Jan Gummert,Anna Gaertner,Franziska Flottmann,Hermann Körperich,Bärbel Klauke,Jörn Kalinowski,Carsten Hain,Lech Paluszkiewicz

doi:10.3390/biomedicines9101400

Abstract

Currently, little is known about the genetic background of restrictive cardiomyopathy (RCM). Herein, we screened an index patient with RCM in combination with atrial fibrillation using a next generation sequencing (NGS) approach and identified the heterozygous mutation DES-c.735G>C. As DES-c.735G>C affects the last base pair of exon-3, it is unknown whether putative missense or splice site mutations are caused. Therefore, we applied nanopore amplicon sequencing revealing the expression of a transcript without exon-3 in the explanted myocardial tissue of the index patient. Western blot analysis verified this finding at the protein level. In addition, we performed cell culture experiments revealing an abnormal cytoplasmic aggregation of the truncated desmin form (p.D214-E245del) but not of the missense variant (p.E245D). In conclusion, we show that DES-c.735G>C causes a splicing defect leading to exon-3 skipping of the DES gene. DES-c.735G>C can be classified as a pathogenic mutation associated with RCM and atrial fibrillation. In the future, this finding might have relevance for the genetic understanding of similar cases.

Highlights

Desmin, encoded by the DES gene, is the major specific intermediate filament (IF)protein
We demonstrated by nanopore sequencing that an in-frame exon skipping is caused by DES-c.735G>C leading to a filament assembly defect of the mutant desmin, which is likely causative for restrictive cardiomyopathy (RCM)
Anamnesis revealed five further family members (I-2, II-1, II-3, II-5, and III-5, Figure 1) affected by cardiomyopathy and/or skeletal myopathy indicating an autosomal-dominant mode of inheritance

Summary

Introduction

Desmin, encoded by the DES gene, is the major specific intermediate filament (IF). Mutations in DES cause different cardiac and skeletal myopathies [1,2] or combinations of both [3]. The exact incidence of pathogenic DES mutations is unknown, desminopathy is a rare disease with an estimated incidence of less than 1 in 2000 [4]. Desmin consists of an α-helical rod domain flanked by non-helical head and tail domains. It forms coiled-coil dimers, which anneal antiparallel into tetramers [5]. Eight antiparallel tetramers form unit-length filaments (ULFs), which are the essential building blocks of intermediate filaments [4]

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Conclusion