title: A mutation in the glutamate-rich region of RNA-binding motif protein 20 causes dilated cardiomyopathy through missplicing of titin and impaired Frank-Starling mechanism.
abstract: Mutations in the RS-domain of RNA-binding motif protein 20 (RBM20) have recently been identified to segregate with aggressive forms of familial dilated cardiomyopathy (DCM). Loss of RBM20 in rats results in missplicing of the sarcomeric gene titin (TTN). The functional and physiological consequences of RBM20 mutations outside the mutational hotspot of RBM20 have not been explored to date. In this study, we investigated the pathomechanism of DCM caused by a novel RBM20 mutation in human cardiomyocytes.
  
  
  
  We identified a family with DCM carrying a mutation (RBM20(E913K/+)) in a glutamate-rich region of RBM20. Western blot analysis of endogenous RBM20 protein revealed strongly reduced protein levels in the heart of an RBM20(E913K/+ )carrier. RNA deep-sequencing demonstrated massive inclusion of exons coding for the spring region of titin in the RBM20(E913K/+ )carrier. Titin isoform analysis revealed a dramatic shift from the less compliant N2B towards the highly compliant N2BA isoforms in RBM20(E913K/+ )heart. Moreover, an increased sarcomere resting-length was observed in single cardiomyocytes and isometric force measurements revealed an attenuated Frank-Starling mechanism (FSM), which was rescued by protein kinase A treatment.
  
  
  
  A mutation outside the mutational hotspot of RBM20 results in haploinsufficiency of RBM20. This leads to disturbed alternative splicing of TTN, resulting in a dramatic shift to highly compliant titin isoforms and an impaired FSM. These effects may contribute to the early onset, and malignant course of DCM caused by RBM20 mutations. Altogether, our results demonstrate that heterozygous loss of RBM20 suffices to profoundly impair myocyte biomechanics by its disturbance of TTN splicing.
authors: Department of Experimental Cardiology, Academic Medical Center, Meibergdreef 15, 1105AZ, Amsterdam, The Netherlands a.beqqali@icloud.com.
authors: Abdelaziz
authors: A
authors: Beqqali
authors: Department of Physiology, VU University Medical Center, Institute for Cardiovascular Research (ICaR-VU), van der Boechorststraat 7, 1081 BT, Amsterdam, The Netherlands.
authors: Ilse A E
authors: IA
authors: Bollen
authors: Department of Cardiology, Aarhus University Hospital, Norrebrogade 44, DK-8000, Aarhus, Denmark.
authors: Torsten B
authors: TB
authors: Rasmussen
authors: Department of Experimental Cardiology, Academic Medical Center, Meibergdreef 15, 1105AZ, Amsterdam, The Netherlands.
authors: Maarten M
authors: MM
authors: van den Hoogenhof
authors: Department of Experimental Cardiology, Academic Medical Center, Meibergdreef 15, 1105AZ, Amsterdam, The Netherlands.
authors: Hanneke W M
authors: HW
authors: van Deutekom
authors: National Heart Research Institute Singapore, National Heart Centre Singapore, 5 Hospital Drive, Singapore 169609, Singapore Division of Cardiovascular & Metabolic Disorders, Duke-National University of Singapore, 8 College Road, Singapore 169857, Singapore.
authors: Sebastian
authors: S
authors: Schafer
authors: Department of Internal Medicine III, Cardiology, University Hospital of Heidelberg, 69120 Heidelberg, Germany DZHK (German Centre for Cardiovascular Research), Oudenarder Straße 16, 13347 Berlin, Germany.
authors: Jan
authors: J
authors: Haas
authors: Department of Internal Medicine III, Cardiology, University Hospital of Heidelberg, 69120 Heidelberg, Germany DZHK (German Centre for Cardiovascular Research), Oudenarder Straße 16, 13347 Berlin, Germany.
authors: Benjamin
authors: B
authors: Meder
authors: Department of Cardiology, Aarhus University Hospital, Norrebrogade 44, DK-8000, Aarhus, Denmark.
authors: Keld E
authors: KE
authors: Sørensen
authors: Department of Experimental Cardiology, Academic Medical Center, Meibergdreef 15, 1105AZ, Amsterdam, The Netherlands.
authors: Ralph J
authors: RJ
authors: van Oort
authors: Department of Cardiology, Odense University Hospital, Sdr. Boulevard 29, 5000 Odense, Denmark.
authors: Jens
authors: J
authors: Mogensen
authors: DZHK (German Centre for Cardiovascular Research), Oudenarder Straße 16, 13347 Berlin, Germany Charité-Universitätsmedizin, Charitéplatz 1, 10117 Berlin, Germany Cardiovascular and Metabolic Sciences, Max-Delbrück-Center for Molecular Medicine (MDC), Robert-Rössle-Str. 10, 13125 Berlin, Germany.
authors: Norbert
authors: N
authors: Hubner
authors: Department of Experimental Cardiology, Academic Medical Center, Meibergdreef 15, 1105AZ, Amsterdam, The Netherlands.
authors: Esther E
authors: EE
authors: Creemers
authors: Department of Physiology, VU University Medical Center, Institute for Cardiovascular Research (ICaR-VU), van der Boechorststraat 7, 1081 BT, Amsterdam, The Netherlands.
authors: Jolanda
authors: J
authors: van der Velden
authors: Department of Experimental Cardiology, Academic Medical Center, Meibergdreef 15, 1105AZ, Amsterdam, The Netherlands.
authors: Yigal M
authors: YM
authors: Pinto
mesh_terms: D000328:Adult; D000368:Aged; D017398:Alternative Splicing; D000818:Animals; D002311:Cardiomyopathy, Dilated / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology; D016022:Case-Control Studies; D002460:Cell Line; D064211:Connectin / Q000235:genetics / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004252:DNA Mutational Analysis; D005260:Female; D056726:Genetic Association Studies; D020022:Genetic Predisposition to Disease; D057895:Haploinsufficiency; D040941:Heredity; D006579:Heterozygote; D006801:Humans; D008297:Male; D008955:Models, Cardiovascular; D009119:Muscle Contraction; D009154:Mutation; D032383:Myocytes, Cardiac / Q000378:metabolism*; D010375:Pedigree; D010641:Phenotype; D010766:Phosphorylation; D020033:Protein Isoforms; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D014162:Transfection
chemical_list: D064211:Connectin; D020033:Protein Isoforms; C573837:RBM20 protein, rat; D016601:RNA-Binding Proteins; C577285:TTN protein, human; C577295:Ttn protein, rat; C543725:ribonucleic acid binding motif protein 20, human; D017868:Cyclic AMP-Dependent Protein Kinases
keywords: Alternative splicing; Cardiomyopathy; Dilated cardiomyopathy; Heart failure; RBM20; Sarcomere