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1.
Sci Rep ; 9(1): 6768, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-31043663

RESUMO

The Coxsackievirus and adenovirus receptor (CAR) is essential for normal electrical conductance in the heart, but its role in the postnatal brain is largely unknown. Using brain specific CAR knockout mice (KO), we discovered an unexpected role of CAR in neuronal communication. This includes increased basic synaptic transmission at hippocampal Schaffer collaterals, resistance to fatigue, and enhanced long-term potentiation. Spontaneous neurotransmitter release and speed of endocytosis are increased in KOs, accompanied by increased expression of the exocytosis associated calcium sensor synaptotagmin 2. Using proximity proteomics and binding studies, we link CAR to the exocytosis machinery as it associates with syntenin and synaptobrevin/VAMP2 at the synapse. Increased synaptic function does not cause adverse effects in KO mice, as behavior and learning are unaffected. Thus, unlike the connexin-dependent suppression of atrioventricular conduction in the cardiac knockout, communication in the CAR deficient brain is improved, suggesting a role for CAR in presynaptic processes.

2.
Eur Heart J ; 2019 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-31004144

RESUMO

AIMS: Heart failure with preserved ejection fraction (HFpEF) and pathological cardiac aging share a complex pathophysiology, including extracellular matrix remodelling (EMR). Protease-activated receptor 2 (PAR2) deficiency is associated with EMR. The roles of PAR1 and PAR2 have not been studied in HFpEF, age-dependent cardiac fibrosis, or diastolic dysfunction (DD). METHODS AND RESULTS: Evaluation of endomyocardial biopsies from patients with HFpEF (n = 14) revealed that a reduced cardiac PAR2 expression was associated with aggravated DD and increased myocardial fibrosis (r = -0.7336, P = 0.0028). In line, 1-year-old PAR2-knockout (PAR2ko) mice suffered from DD with preserved systolic function, associated with an increased age-dependent α-smooth muscle actin expression, collagen deposition (1.7-fold increase, P = 0.0003), lysyl oxidase activity, collagen cross-linking (2.2-fold increase, P = 0.0008), endothelial activation, and inflammation. In the absence of PAR2, the receptor-regulating protein caveolin-1 was down-regulated, contributing to an augmented profibrotic PAR1 and transforming growth factor beta (TGF-ß)-dependent signalling. This enhanced TGF-ß/PAR1 signalling caused N-proteinase (ADAMTS3) and C-proteinase (BMP1)-related increased collagen I production from cardiac fibroblasts (CFs). PAR2 overexpression in PAR2ko CFs reversed these effects. The treatment with the PAR1 antagonist, vorapaxar, reduced cardiac fibrosis by 44% (P = 0.03) and reduced inflammation in a metabolic disease model (apolipoprotein E-ko mice). Patients with HFpEF with upstream PAR inhibition via FXa inhibitors (n = 40) also exhibited reduced circulating markers of fibrosis and DD compared with patients treated with vitamin K antagonists (n = 20). CONCLUSIONS: Protease-activated receptor 2 is an important regulator of profibrotic PAR1 and TGF-ß signalling in the heart. Modulation of the FXa/FIIa-PAR1/PAR2/TGF-ß-axis might be a promising therapeutic approach to reduce HFpEF.

3.
Circulation ; 139(15): 1813-1827, 2019 Apr 09.
Artigo em Inglês | MEDLINE | ID: mdl-30700140

RESUMO

BACKGROUND: Titin is a giant elastic protein that spans the half-sarcomere from Z-disk to M-band. It acts as a molecular spring and mechanosensor and has been linked to striated muscle disease. The pathways that govern titin-dependent cardiac growth and contribute to disease are diverse and difficult to dissect. METHODS: To study titin deficiency versus dysfunction, the authors generated and compared striated muscle specific knockouts (KOs) with progressive postnatal loss of the complete titin protein by removing exon 2 (E2-KO) or an M-band truncation that eliminates proper sarcomeric integration, but retains all other functional domains (M-band exon 1/2 [M1/2]-KO). The authors evaluated cardiac function, cardiomyocyte mechanics, and the molecular basis of the phenotype. RESULTS: Skeletal muscle atrophy with reduced strength, severe sarcomere disassembly, and lethality from 2 weeks of age were shared between the models. Cardiac phenotypes differed considerably: loss of titin leads to dilated cardiomyopathy with combined systolic and diastolic dysfunction-the absence of M-band titin to cardiac atrophy and preserved function. The elastic properties of M1/2-KO cardiomyocytes are maintained, while passive stiffness is reduced in the E2-KO. In both KOs, we find an increased stress response and increased expression of proteins linked to titin-based mechanotransduction (CryAB, ANKRD1, muscle LIM protein, FHLs, p42, Camk2d, p62, and Nbr1). Among them, FHL2 and the M-band signaling proteins p62 and Nbr1 are exclusively upregulated in the E2-KO, suggesting a role in the differential pathology of titin truncation versus deficiency of the full-length protein. The differential stress response is consistent with truncated titin contributing to the mechanical properties in M1/2-KOs, while low titin levels in E2-KOs lead to reduced titin-based stiffness and increased strain on the remaining titin molecules. CONCLUSIONS: Progressive depletion of titin leads to sarcomere disassembly and atrophy in striated muscle. In the complete knockout, remaining titin molecules experience increased strain, resulting in mechanically induced trophic signaling and eventually dilated cardiomyopathy. The truncated titin in M1/2-KO helps maintain the passive properties and thus reduces mechanically induced signaling. Together, these findings contribute to the molecular understanding of why titin mutations differentially affect cardiac growth and have implications for genotype-phenotype relations that support a personalized medicine approach to the diverse titinopathies.

4.
J Gen Physiol ; 151(1): 42-52, 2019 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-30567709

RESUMO

Heart failure with preserved ejection fraction (HFpEF) is a complex syndrome characterized by a preserved ejection fraction but increased diastolic stiffness and abnormalities of filling. Although the prevalence of HFpEF is high and continues to rise, no effective therapies exist; however, the diabetic drug metformin has been associated with improved diastolic function in diabetic patients. Here we determine the therapeutic potential of metformin for improving diastolic function in a mouse model with HFpEF-like symptoms. We combine transverse aortic constriction (TAC) surgery with deoxycorticosterone acetate (DOCA) supplementation to obtain a mouse model with increased diastolic stiffness and exercise intolerance. Echocardiography and pressure-volume analysis reveal that providing metformin to TAC/DOCA mice improves diastolic function in the left ventricular (LV) chamber. Muscle mechanics show that metformin lowers passive stiffness of the LV wall muscle. Concomitant with this improvement in diastolic function, metformin-treated TAC/DOCA mice also demonstrate preserved exercise capacity. No metformin effects are seen in sham operated mice. Extraction experiments on skinned ventricular muscle strips show that the metformin-induced reduction of passive stiffness in TAC/DOCA mice is due to an increase in titin compliance. Using phospho-site-specific antibodies, we assay the phosphorylation of titin's PEVK and N2B spring elements. Metformin-treated mice have unaltered PEVK phosphorylation but increased phosphorylation of PKA sites in the N2B element, a change which has previously been shown to lower titin's stiffness. Consistent with this result, experiments with a mouse model deficient in the N2B element reveal that the beneficial effect of metformin on LV chamber and muscle stiffness requires the presence of the N2B element. We conclude that metformin offers therapeutic benefit during HFpEF by lowering titin-based passive stiffness.

5.
PLoS One ; 13(6): e0198492, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29889873

RESUMO

Diastolic dysfunction is increasingly prevalent in our ageing society and an important contributor to heart failure. The giant protein titin could serve as a therapeutic target, as its elastic properties are a main determinant of cardiac filling in diastole. This study aimed to develop a high throughput pharmacological screen to identify small molecules that affect titin isoform expression through differential inclusion of exons encoding the elastic PEVK domains. We used a dual luciferase splice reporter assay that builds on the titin splice factor RBM20 to screen ~34,000 small molecules and identified several compounds that inhibit the exclusion of PEVK exons. These compounds belong to the class of cardenolides and affect RBM20 dependent titin exon exclusion but did not affect RBFOX1 mediated splicing of FMNL3. We provide evidence that cardenolides do not bind to the RNA interacting domain of RBM20, but reduce RBM20 protein levels and alter transcription of select splicing factors that interact with RBM20. Cardenolides affect titin isoform expression. Understanding their mode of action and harnessing the splice effects through chemical modifications that suppress the effects on ion homeostasis and more selectively affect cardiac splicing has the potential to improve cardiac filling and thus help patients with diastolic heart failure, for which currently no targeted therapy exists.

6.
Hum Mol Genet ; 2018 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-29893868

RESUMO

Mutations in the lamin A/C gene (LMNA) cause an autosomal dominant inherited form of dilated cardiomyopathy associated with cardiac conduction disease (hereafter referred to as LMNA cardiomyopathy). Compared with other forms of dilated cardiomyopathy, mutations in LMNA are responsible for a more aggressive clinical course due to a high rate of malignant ventricular arrhythmias. Gap junctions are intercellular channels that allow direct communication between neighboring cells, which are involved in electrical impulse propagation and coordinated contraction of the heart. For gap junctions to properly control electrical synchronization in the heart, connexin-based hemichannels must be correctly targeted to intercalated discs, Cx43 being the major connexin in the working myocytes. We here showed an altered distribution of Cx43 in a mouse model of LMNA cardiomyopathy. However, little is known on the molecular mechanisms of Cx43 remodeling in pathological context. We now show that microtubule cytoskeleton alteration and decreased acetylation of α-tubulin lead to remodeling of Cx43 in LMNA cardiomyopathy, which alters the correct communication between cardiomyocytes, ultimately leading to electrical conduction disturbances. Preventing or reversing this process could offer a strategy to repair damaged heart. Stabilization of microtubule cytoskeleton using Paclitaxel improved intraventricular conduction defects. These results indicate that microtubule cytoskeleton contributes to the pathogenesis of LMNA cardiomyopathy and that drugs stabilizing the microtubule may be beneficial for patients.

7.
Nucleic Acids Res ; 46(10): 5227-5238, 2018 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-29518215

RESUMO

RNA-binding motif protein 20 (RBM20) is a cardiac splice regulator that adapts cardiac filling via its diverse substrates-including the sarcomeric protein titin. The molecular basis and regulation of RBM20-dependent exon exclusion are largely unknown. In tissue culture experiments, we show that the combination of RNA recognition motif (RRM) and C-terminus is necessary and sufficient for RBM20 activity, indicating an important function of the ZnF2 domain in splicing repression. Using splice reporter and in vitro binding assays targeting titin exons 241-243, we identified a minimal genomic segment that is necessary for RBM20-mediated splicing repression of the alternative exon. Here, RBM20 binds the cluster containing most RBM20 binding motifs through its RRM domain and represses the upstream and downstream introns. For subsequent exon exclusion, specific regions upstream, downstream and within the alternative exon 242 are required. Regulation of exon exclusion involves PTB4 as a novel titin splice regulator, which counteracts RBM20 repressor activity in HEK293 cells. Together, these mechanistic insights into the regulation and action of RBM20 and PTB4 provide a basis for the future development of RBM20 modulators that adapt titin elasticity in cardiac disease.

8.
RNA Biol ; 15(3): 359-368, 2018 03 04.
Artigo em Inglês | MEDLINE | ID: mdl-29028411

RESUMO

PAR-CLIP (photoactivatable ribonucleoside-enhanced crosslinking and immunoprecipitation) facilitates the identification and mapping of protein/RNA interactions. So far, it has been limited to select cell-lines as it requires efficient 4SU uptake. To increase transcriptome complexity and thus identify additional RNA-protein interaction sites we fused HEK 293 T-Rex cells (HEK293-Y) that express the RNA binding protein YBX1 with PC12 cells expressing eGFP (PC12-eGFP). The resulting hybrids enable PAR-CLIP on a neuronally expanded transcriptome (Fusion-CLIP) and serve as a proof of principle. The fusion cells express both parental marker genes YBX1 and eGFP and the expanded transcriptome contains human and rat transcripts. PAR-CLIP of fused cells versus the parental HEK293-Y identified 768 novel RNA targets of YBX1. We were able to trace the origin of the majority of the short PAR-CLIP reads as they differentially mapped to the human and rat genome. Furthermore, Fusion-CLIP expanded the CAUC RNA binding motif of YBX1 to UCUUUNNCAUC. The fusion of HEK293-Y and PC12-eGFP cells resulted in cells with a diverse genome expressing human and rat transcripts that enabled the identification of novel YBX1 substrates. The technique allows the expansion of the HEK 293 transcriptome and makes PAR-CLIP available to fusion cells of diverse origin.


Assuntos
Fusão Celular/métodos , Proteínas de Fluorescência Verde/química , Proteínas de Fluorescência Verde/metabolismo , RNA Mensageiro/metabolismo , Proteína 1 de Ligação a Y-Box/química , Proteína 1 de Ligação a Y-Box/metabolismo , Motivos de Aminoácidos , Animais , Sítios de Ligação , Reagentes para Ligações Cruzadas , Perfilação da Expressão Gênica/métodos , Células HEK293 , Humanos , Imunoprecipitação , Células PC12 , Ligação Proteica , Ratos
9.
Eur Heart J ; 38(46): 3449-3460, 2017 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-29029073

RESUMO

Aims: In this study, we aimed to clinically and genetically characterize LVNC patients and investigate the prevalence of variants in known and novel LVNC disease genes. Introduction: Left ventricular non-compaction cardiomyopathy (LVNC) is an increasingly recognized cause of heart failure, arrhythmia, thromboembolism, and sudden cardiac death. We sought here to dissect its genetic causes, phenotypic presentation and outcome. Methods and results: In our registry with follow-up of in the median 61 months, we analysed 95 LVNC patients (68 unrelated index patients and 27 affected relatives; definite familial LVNC = 23.5%) by cardiac phenotyping, molecular biomarkers and exome sequencing. Cardiovascular events were significantly more frequent in LVNC patients compared with an age-matched group of patients with non-ischaemic dilated cardiomyopathy (hazard ratio = 2.481, P = 0.002). Stringent genetic classification according to ACMG guidelines revealed that TTN, LMNA, and MYBPC3 are the most prevalent disease genes (13 patients are carrying a pathogenic truncating TTN variant, odds ratio = 40.7, Confidence interval = 21.6-76.6, P < 0.0001, percent spliced in 76-100%). We also identified novel candidate genes for LVNC. For RBM20, we were able to perform detailed familial, molecular and functional studies. We show that the novel variant p.R634L in the RS domain of RBM20 co-segregates with LVNC, leading to titin mis-splicing as revealed by RNA sequencing of heart tissue in mutation carriers, protein analysis, and functional splice-reporter assays. Conclusion: Our data demonstrate that the clinical course of symptomatic LVNC can be severe. The identified pathogenic variants and distribution of disease genes-a titin-related pathomechanism is found in every fourth patient-should be considered in genetic counselling of patients. Pathogenic variants in the nuclear proteins Lamin A/C and RBM20 were associated with worse outcome.


Assuntos
Hipertrofia Ventricular Esquerda/genética , Mutação/genética , Adulto , Arritmias Cardíacas/genética , Cardiomiopatia Dilatada/genética , Conectina/genética , Morte Súbita Cardíaca/etiologia , Feminino , Predisposição Genética para Doença/genética , Humanos , Lamina Tipo A/genética , Masculino , Linhagem , Proteínas de Ligação a RNA/genética
10.
Science ; 356(6335): 307-311, 2017 04 21.
Artigo em Inglês | MEDLINE | ID: mdl-28428423

RESUMO

The African naked mole-rat's (Heterocephalus glaber) social and subterranean lifestyle generates a hypoxic niche. Under experimental conditions, naked mole-rats tolerate hours of extreme hypoxia and survive 18 minutes of total oxygen deprivation (anoxia) without apparent injury. During anoxia, the naked mole-rat switches to anaerobic metabolism fueled by fructose, which is actively accumulated and metabolized to lactate in the brain. Global expression of the GLUT5 fructose transporter and high levels of ketohexokinase were identified as molecular signatures of fructose metabolism. Fructose-driven glycolytic respiration in naked mole-rat tissues avoids feedback inhibition of glycolysis via phosphofructokinase, supporting viability. The metabolic rewiring of glycolysis can circumvent the normally lethal effects of oxygen deprivation, a mechanism that could be harnessed to minimize hypoxic damage in human disease.


Assuntos
Adaptação Fisiológica , Anaerobiose , Encéfalo/fisiologia , Frutose/metabolismo , Glicólise , Ratos-Toupeira/metabolismo , Oxigênio/metabolismo , Animais , Encéfalo/metabolismo , Frutoquinases/metabolismo , Transportador de Glucose Tipo 5/metabolismo , Ácido Láctico/metabolismo , Camundongos , Miocárdio/metabolismo , Sacarose/metabolismo
11.
J Mol Med (Berl) ; 94(12): 1349-1358, 2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-27889803

RESUMO

Impaired diastolic filling is a main contributor to heart failure with preserved ejection fraction (HFpEF), a syndrome with increasing prevalence and no treatment. Both collagen and the giant sarcomeric protein titin determine diastolic function. Since titin's elastic properties can be adjusted physiologically, we evaluated titin-based stiffness as a therapeutic target. We adjusted RBM20-dependent cardiac isoform expression in the titin N2B knockout mouse with increased ventricular stiffness. A ~50 % reduction of RBM20 activity does not only maintain cardiac filling in diastole but also ameliorates cardiac atrophy and thus improves cardiac function in the N2B-deficient heart. Reduced RBM20 activity partially normalized gene expression related to muscle development and fatty acid metabolism. The adaptation of cardiac growth was related to hypertrophy signaling via four-and-a-half lim-domain proteins (FHLs) that translate mechanical input into hypertrophy signals. We provide a novel link between cardiac isoform expression and trophic signaling via FHLs and suggest cardiac splicing as a therapeutic target in diastolic dysfunction. KEY MESSAGE: Increasing the length of titin isoforms improves ventricular filling in heart disease. FHL proteins are regulated via RBM20 and adapt cardiac growth. RBM20 is a therapeutic target in diastolic dysfunction.


Assuntos
Cardiomegalia/metabolismo , Insuficiência Cardíaca/metabolismo , Ventrículos do Coração/metabolismo , Proteínas Quinases/genética , Proteínas de Ligação a RNA/genética , Animais , Cardiomegalia/genética , Cardiomegalia/patologia , Colágeno/genética , Colágeno/metabolismo , Diástole/fisiologia , Regulação da Expressão Gênica , Insuficiência Cardíaca/genética , Insuficiência Cardíaca/patologia , Ventrículos do Coração/patologia , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas com Domínio LIM/genética , Proteínas com Domínio LIM/metabolismo , Masculino , Camundongos , Camundongos Knockout , Proteínas Musculares/genética , Proteínas Musculares/metabolismo , Miocárdio/metabolismo , Miocárdio/patologia , Proteínas Quinases/deficiência , Proteínas de Ligação a RNA/metabolismo , Transdução de Sinais , Volume Sistólico/fisiologia
12.
J Clin Invest ; 126(10): 3999-4015, 2016 10 03.
Artigo em Inglês | MEDLINE | ID: mdl-27643434

RESUMO

The canonical atrial myocyte (AM) is characterized by sparse transverse tubule (TT) invaginations and slow intracellular Ca2+ propagation but exhibits rapid contractile activation that is susceptible to loss of function during hypertrophic remodeling. Here, we have identified a membrane structure and Ca2+-signaling complex that may enhance the speed of atrial contraction independently of phospholamban regulation. This axial couplon was observed in human and mouse atria and is composed of voluminous axial tubules (ATs) with extensive junctions to the sarcoplasmic reticulum (SR) that include ryanodine receptor 2 (RyR2) clusters. In mouse AM, AT structures triggered Ca2+ release from the SR approximately 2 times faster at the AM center than at the surface. Rapid Ca2+ release correlated with colocalization of highly phosphorylated RyR2 clusters at AT-SR junctions and earlier, more rapid shortening of central sarcomeres. In contrast, mice expressing phosphorylation-incompetent RyR2 displayed depressed AM sarcomere shortening and reduced in vivo atrial contractile function. Moreover, left atrial hypertrophy led to AT proliferation, with a marked increase in the highly phosphorylated RyR2-pS2808 cluster fraction, thereby maintaining cytosolic Ca2+ signaling despite decreases in RyR2 cluster density and RyR2 protein expression. AT couplon "super-hubs" thus underlie faster excitation-contraction coupling in health as well as hypertrophic compensatory adaptation and represent a structural and metabolic mechanism that may contribute to contractile dysfunction and arrhythmias.


Assuntos
Sinalização do Cálcio , Átrios do Coração/citologia , Miócitos Cardíacos/fisiologia , Agonistas Adrenérgicos beta/farmacologia , Animais , Cálcio/metabolismo , Células Cultivadas , Humanos , Junções Intercelulares/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Knockout , Microtúbulos/metabolismo , Contração Miocárdica , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/ultraestrutura , Fosforilação , Processamento de Proteína Pós-Traducional , Transporte Proteico , Canal de Liberação de Cálcio do Receptor de Rianodina
13.
PLoS One ; 10(6): e0129424, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26076477

RESUMO

The coxsackie- and adenovirus receptor (CXADR) is a member of the immunoglobulin protein superfamily, present in various epithelial cells including glomerular epithelial cells. Beside its known function as a virus receptor, it also constitutes an integral part of cell-junctions. Previous studies in the zebrafish pronephros postulated a potential role of CXADR for the terminal differentiation of glomerular podocytes and correct patterning of the elaborated foot process architecture. However, due to early embryonic lethality of constitutive Cxadr knockout mice, mammalian data on kidney epithelial cells have been lacking. Interestingly, Cxadr is robustly expressed during podocyte development and in adulthood in response to glomerular injury. We therefore used a conditional transgenic approach to elucidate the function of Cxadr for podocyte development and stress response. Surprisingly, we could not discern a developmental phenotype in podocyte specific Cxadr knock-out mice. In addition, despite a significant up regulation of CXADR during toxic, genetic and immunologic podocyte injury, we could not detect any impact of Cxadr on these injury models. Thus these data indicate that in contrast to lower vertebrate models, mammalian podocytes have acquired molecular programs to compensate for the loss of Cxadr.


Assuntos
Proteína de Membrana Semelhante a Receptor de Coxsackie e Adenovirus/genética , Proteína de Membrana Semelhante a Receptor de Coxsackie e Adenovirus/metabolismo , Deleção de Genes , Podócitos/metabolismo , Estresse Fisiológico , Animais , Expressão Gênica , Técnicas de Inativação de Genes , Rim/embriologia , Rim/metabolismo , Glomérulos Renais/citologia , Glomérulos Renais/embriologia , Glomérulos Renais/metabolismo , Glomérulos Renais/ultraestrutura , Camundongos , Camundongos Knockout
14.
Sci Transl Med ; 7(270): 270ra6, 2015 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-25589632

RESUMO

The recent discovery of heterozygous human mutations that truncate full-length titin (TTN, an abundant structural, sensory, and signaling filament in muscle) as a common cause of end-stage dilated cardiomyopathy (DCM) promises new prospects for improving heart failure management. However, realization of this opportunity has been hindered by the burden of TTN-truncating variants (TTNtv) in the general population and uncertainty about their consequences in health or disease. To elucidate the effects of TTNtv, we coupled TTN gene sequencing with cardiac phenotyping in 5267 individuals across the spectrum of cardiac physiology and integrated these data with RNA and protein analyses of human heart tissues. We report diversity of TTN isoform expression in the heart, define the relative inclusion of TTN exons in different isoforms (using the TTN transcript annotations available at http://cardiodb.org/titin), and demonstrate that these data, coupled with the position of the TTNtv, provide a robust strategy to discriminate pathogenic from benign TTNtv. We show that TTNtv is the most common genetic cause of DCM in ambulant patients in the community, identify clinically important manifestations of TTNtv-positive DCM, and define the penetrance and outcomes of TTNtv in the general population. By integrating genetic, transcriptome, and protein analyses, we provide evidence for a length-dependent mechanism of disease. These data inform diagnostic criteria and management strategies for TTNtv-positive DCM patients and for TTNtv that are identified as incidental findings.


Assuntos
Alelos , Conectina/genética , Coração/fisiologia , Mutação , Transcrição Genética , Adolescente , Adulto , Idoso , Cardiomiopatia Dilatada/genética , Cardiomiopatia Dilatada/patologia , Estudos de Coortes , Conectina/fisiologia , Éxons , Variação Genética , Voluntários Saudáveis , Insuficiência Cardíaca/genética , Insuficiência Cardíaca/terapia , Humanos , Imunoglobulinas/metabolismo , Pessoa de Meia-Idade , Isoformas de Proteínas/genética , Isoformas de Proteínas/fisiologia , Adulto Jovem
15.
J Biol Chem ; 290(4): 2419-30, 2015 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-25488665

RESUMO

Src homology and collagen A (ShcA) is an adaptor protein that binds to tyrosine kinase receptors. Its germ line deletion is embryonic lethal with abnormal cardiovascular system formation, and its role in cardiovascular development is unknown. To investigate its functional role in cardiovascular development in mice, ShcA was deleted in cardiomyocytes and vascular smooth muscle cells by crossing ShcA flox mice with SM22a-Cre transgenic mice. Conditional mutant mice developed signs of severe dilated cardiomyopathy, myocardial infarctions, and premature death. No evidence of a vascular contribution to the phenotype was observed. Histological analysis of the heart revealed aberrant sarcomeric Z-disk and M-band structures, and misalignments of T-tubules with Z-disks. We find that not only the ErbB3/Neuregulin signaling pathway but also the baroreceptor reflex response, which have been functionally associated, are altered in the mutant mice. We further demonstrate that ShcA interacts with Caveolin-1 and the costameric protein plasma membrane Ca(2+)/calmodulin-dependent ATPase (PMCA), and that its deletion leads to abnormal dystrophin signaling. Collectively, these results demonstrate that ShcA interacts with crucial proteins and pathways that link Z-disk and costamere.


Assuntos
Costâmeros/metabolismo , Coração/embriologia , Miócitos Cardíacos/metabolismo , Miócitos de Músculo Liso/metabolismo , Proteínas Adaptadoras da Sinalização Shc/metabolismo , Alelos , Animais , Aorta Torácica/metabolismo , Pressão Sanguínea , Sobrevivência Celular , Distrofina/metabolismo , Ecocardiografia , Deleção de Genes , Regulação da Expressão Gênica no Desenvolvimento , Imagem por Ressonância Magnética , Camundongos , Camundongos Transgênicos , Microscopia Confocal , Fenótipo , ATPases Transportadoras de Cálcio da Membrana Plasmática/metabolismo , RNA Interferente Pequeno/metabolismo , Ratos , Receptor ErbB-3/metabolismo , Proteínas Adaptadoras da Sinalização Shc/genética , Proteína 1 de Transformação que Contém Domínio 2 de Homologia de Src
16.
Sci Rep ; 4: 7430, 2014 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-25503263

RESUMO

Non-physiological activation of the mineralocorticoid receptor (MR), e.g. by aldosterone under conditions of high salt intake, contributes to the pathogenesis of cardiovascular diseases, although beneficial effects of aldosterone also have been described. The epidermal growth factor receptor (EGFR) contributes to cardiovascular alterations and mediates part of the MR effects. Recently, we showed that EGFR is required for physiological homeostasis and function of heart and arteries in adult animals. We hypothesize that moderate high aldosterone/NaCl, at normal blood pressure, affects the cardiovascular system depending on cardiovascular EGFR. Therefore we performed an experimental series in male and female animals each, using a recently established mouse model with EGFR knockout in vascular smooth muscle cells and cardiomyocytes and determined the effects of a mild-high aldosterone-to-NaCl constellation on a.o. marker gene expression, heart size, systolic blood pressure, impulse conduction and heart rate. Our data show that (i) cardiac tissue of male but not of female mice is sensitive to mild aldosterone/NaCl treatment, (ii) EGFR knockout induces stronger cardiac disturbances in male as compared to female animals and (iii) mild aldosterone/NaCl treatment requires the EGFR in order to disturb cardiac tissue homeostasis whereas beneficial effects of aldosterone seem to be independent of EGFR.


Assuntos
Aldosterona/fisiologia , Receptores ErbB/fisiologia , Miocárdio/metabolismo , Cloreto de Sódio/metabolismo , Aldosterona/farmacologia , Animais , Biomarcadores/metabolismo , Feminino , Homeostase , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Cloreto de Sódio/farmacologia , Transcriptoma
17.
J Cell Sci ; 127(Pt 17): 3666-74, 2014 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-24982444

RESUMO

Cardiac titin is the main determinant of sarcomere stiffness during diastolic relaxation. To explore whether titin stiffness affects the kinetics of cardiac myofibrillar contraction and relaxation, we used subcellular myofibrils from the left ventricles of homozygous and heterozygous N2B-knockout mice which express truncated cardiac titins lacking the unique elastic N2B region. Compared with myofibrils from wild-type mice, myofibrils from knockout and heterozygous mice exhibit increased passive myofibrillar stiffness. To determine the kinetics of Ca(2+)-induced force development (rate constant kACT), myofibrils from knockout, heterozygous and wild-type mice were stretched to the same sarcomere length (2.3 µm) and rapidly activated with Ca(2+). Additionally, mechanically induced force-redevelopment kinetics (rate constant kTR) were determined by slackening and re-stretching myofibrils during Ca(2+)-mediated activation. Myofibrils from knockout mice exhibited significantly higher kACT, kTR and maximum Ca(2+)-activated tension than myofibrils from wild-type mice. By contrast, the kinetic parameters of biphasic force relaxation induced by rapidly reducing [Ca(2+)] were not significantly different among the three genotypes. These results indicate that increased titin stiffness promotes myocardial contraction by accelerating the formation of force-generating cross-bridges without decelerating relaxation.


Assuntos
Conectina/metabolismo , Relaxamento Muscular/fisiologia , Contração Miocárdica/fisiologia , Miofibrilas/metabolismo , Sarcômeros/metabolismo , Deleção de Sequência/genética , Animais , Sequência de Bases/genética , Cálcio/metabolismo , Conectina/genética , Cinética , Camundongos , Contração Miocárdica/genética , Miocárdio/metabolismo , Miofibrilas/fisiologia
18.
J Clin Invest ; 124(8): 3419-30, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-24960161

RESUMO

Mutations in the gene encoding the RNA-binding protein RBM20 have been implicated in dilated cardiomyopathy (DCM), a major cause of chronic heart failure, presumably through altering cardiac RNA splicing. Here, we combined transcriptome-wide crosslinking immunoprecipitation (CLIP-seq), RNA-seq, and quantitative proteomics in cell culture and rat and human hearts to examine how RBM20 regulates alternative splicing in the heart. Our analyses revealed the presence of a distinct RBM20 RNA-recognition element that is predominantly found within intronic binding sites and linked to repression of exon splicing with RBM20 binding near 3' and 5' splice sites. Proteomic analysis determined that RBM20 interacts with both U1 and U2 small nuclear ribonucleic particles (snRNPs) and suggested that RBM20-dependent splicing repression occurs through spliceosome stalling at complex A. Direct RBM20 targets included several genes previously shown to be involved in DCM as well as genes not typically associated with this disease. In failing human hearts, reduced expression of RBM20 affected alternative splicing of several direct targets, indicating that differences in RBM20 expression may affect cardiac function. Together, these findings identify RBM20-regulated targets and provide insight into the pathogenesis of human heart failure.


Assuntos
Processamento Alternativo , Miocárdio/metabolismo , Precursores de RNA/metabolismo , Proteínas de Ligação a RNA/metabolismo , Animais , Sequência de Bases , Sítios de Ligação/genética , Cardiomiopatia Dilatada/complicações , Cardiomiopatia Dilatada/genética , Cardiomiopatia Dilatada/metabolismo , Estudos de Coortes , Éxons , Insuficiência Cardíaca/etiologia , Insuficiência Cardíaca/genética , Insuficiência Cardíaca/metabolismo , Humanos , Mutação , Miócitos Cardíacos/metabolismo , Precursores de RNA/genética , Processamento Pós-Transcricional do RNA , Sítios de Splice de RNA , Proteínas de Ligação a RNA/genética , Ratos , Ratos Sprague-Dawley , Ribonucleoproteína Nuclear Pequena U1/metabolismo , Ribonucleoproteína Nuclear Pequena U2/metabolismo , Seleção Genética , Spliceossomos/metabolismo
19.
J Virol ; 88(13): 7345-56, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-24741103

RESUMO

UNLABELLED: The coxsackievirus and adenovirus receptor (CAR) is a cell contact protein with an important role in virus uptake. Its extracellular immunoglobulin domains mediate the binding to coxsackievirus and adenovirus as well as homophilic and heterophilic interactions between cells. The cytoplasmic tail links CAR to the cytoskeleton and intracellular signaling cascades. In the heart, CAR is crucial for embryonic development, electrophysiology, and coxsackievirus B infection. Noncardiac functions are less well understood, in part due to the lack of suitable animal models. Here, we generated a transgenic mouse that rescued the otherwise embryonic-lethal CAR knockout (KO) phenotype by expressing chicken CAR exclusively in the heart. Using this rescue model, we addressed interspecies differences in coxsackievirus uptake and noncardiac functions of CAR. Survival of the noncardiac CAR KO (ncKO) mouse indicates an essential role for CAR in the developing heart but not in other tissues. In adult animals, cardiac activity was normal, suggesting that chicken CAR can replace the physiological functions of mouse CAR in the cardiomyocyte. However, chicken CAR did not mediate virus entry in vivo, so that hearts expressing chicken instead of mouse CAR were protected from infection and myocarditis. Comparison of sequence homology and modeling of the D1 domain indicate differences between mammalian and chicken CAR that relate to the sites important for virus binding but not those involved in homodimerization. Thus, CAR-directed anticoxsackievirus therapy with only minor adverse effects in noncardiac tissue could be further improved by selectively targeting the virus-host interaction while maintaining cardiac function. IMPORTANCE: Coxsackievirus B3 (CVB3) is one of the most common human pathogens causing myocarditis. Its receptor, the coxsackievirus and adenovirus receptor (CAR), not only mediates virus uptake but also relates to cytoskeletal organization and intracellular signaling. Animals without CAR die prenatally with major cardiac malformations. In the adult heart, CAR is important for virus entry and electrical conduction, but its nonmuscle functions are largely unknown. Here, we show that chicken CAR expression exclusively in the heart can rescue the otherwise embryonic-lethal CAR knockout phenotype but does not support CVB3 infection of adult cardiomyocytes. Our findings have implications for the evolution of virus-host versus physiological interactions involving CAR and could help to improve future coxsackievirus-directed therapies inhibiting virus replication while maintaining CAR's cellular functions.


Assuntos
Proteína de Membrana Semelhante a Receptor de Coxsackie e Adenovirus/fisiologia , Infecções por Coxsackievirus/prevenção & controle , Coração/fisiologia , Miocardite/prevenção & controle , Replicação Viral , Animais , Western Blotting , Células Cultivadas , Galinhas , Infecções por Coxsackievirus/virologia , Enterovirus Humano B/fisiologia , Imunofluorescência , Células HeLa , Coração/virologia , Humanos , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Miocardite/virologia
20.
Hum Mol Genet ; 23(4): 980-91, 2014 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-24105469

RESUMO

Core myopathies (CM), the main non-dystrophic myopathies in childhood, remain genetically unexplained in many cases. Heart disease is not considered part of the typical CM spectrum. No congenital heart defect has been reported, and childhood-onset cardiomyopathy has been documented in only two CM families with homozygous mutations of the TTN gene. TTN encodes titin, a giant protein of striated muscles. Recently, heterozygous TTN truncating mutations have also been reported as a major cause of dominant dilated cardiomyopathy. However, relatively few TTN mutations and phenotypes are known, and titin pathophysiological role in cardiac and skeletal muscle conditions is incompletely understood. We analyzed a series of 23 families with congenital CM and primary heart disease using TTN M-line-targeted sequencing followed in selected patients by whole-exome sequencing and functional studies. We identified seven novel homozygous or compound heterozygous TTN mutations (five in the M-line, five truncating) in 17% patients. Heterozygous parents were healthy. Phenotype analysis identified four novel titinopathies, including cardiac septal defects, left ventricular non-compaction, Emery-Dreifuss muscular dystrophy or arthrogryposis. Additionally, in vitro studies documented the first-reported absence of a functional titin kinase domain in humans, leading to a severe antenatal phenotype. We establish that CM are associated with a large range of heart conditions of which TTN mutations are a major cause, thereby expanding the TTN mutational and phenotypic spectrum. Additionally, our results suggest titin kinase implication in cardiac morphogenesis and demonstrate that heterozygous TTN truncating mutations may not manifest unless associated with a second mutation, reassessing the paradigm of their dominant expression.


Assuntos
Códon sem Sentido , Conectina/genética , Cardiopatias/genética , Miopatia da Parte Central/genética , Adolescente , Conectina/metabolismo , Consanguinidade , Feminino , Genes Recessivos , Estudos de Associação Genética , Predisposição Genética para Doença , Cardiopatias/metabolismo , Cardiopatias/patologia , Heterozigoto , Humanos , Masculino , Músculo Esquelético/metabolismo , Músculo Esquelético/patologia , Miopatia da Parte Central/metabolismo , Miopatia da Parte Central/patologia , Linhagem , Fenótipo , Adulto Jovem
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