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Kidney & Blood Pressure Research Jun 2024A hereditary condition primarily affecting the kidneys and heart has newly been identified: the RRAGD-associated Autosomal Dominant Kidney Hypomagnesemia with... (Review)
Review
BACKGROUND
A hereditary condition primarily affecting the kidneys and heart has newly been identified: the RRAGD-associated Autosomal Dominant Kidney Hypomagnesemia with Cardiomyopathy (ADKH-RRAGD). This disorder is characterized by renal loss of magnesium and potassium, coupled with varying degrees of cardiac dysfunction. These range from arrhythmias to severe dilated cardiomyopathy, which may require heart transplantation. Mutations associated with RRAGD significantly disrupt the non-canonical branch of the mTORC1 pathway. This disruption hinders the the nuclear translocation and transcriptional activity of the transcription factor EB (TFEB) a crucial regulator of lysosomal and autophagic function.
SUMMARY
All identified RRAGD variants compromise kidney function, leading to hypomagnesemia and hypokalemia of various severity. The renal phenotype for most of the variants (i.e. S76L, I221K, P119R, P119L), typically manifests in the second decade of life occasionally preceded by childhood symptoms of dilated cardiomyopathy. In contrast, the P88L variant is associated to dilated cardiomyopathy manifesting in adulthood. To date, the T97P variant has not been linked to cardiac involvement. The most severe manifestations of ADKH-RRAGD, particularly concerning electrolyte imbalance and heart dysfunction requiring transplantation in childhood appear to be associated with the S76L, I221K, P119R variants.
KEY MESSAGES
This review aims to provide an overview of the clinical presentation for ADKH-RRAGD, aiming to enhance o awareness, promote early diagnosis and facilitate proper treatment. It also reports on the limited experience in patient management with diuretics, magnesium and potassium supplements, metformin, or calcineurin- and SGLT2-inhibitors.
PubMed: 38901414
DOI: 10.1159/000539889 -
Diagnostics (Basel, Switzerland) Jun 2024Non-ischemic dilated cardiomyopathy (DCM) represents a significant cause of heart failure, defined as the presence of left ventricular (LV) dilatation and systolic... (Review)
Review
Non-ischemic dilated cardiomyopathy (DCM) represents a significant cause of heart failure, defined as the presence of left ventricular (LV) dilatation and systolic dysfunction unexplained solely by abnormal loading conditions or coronary artery disease. Cardiac resynchronization therapy (CRT) has emerged as a cornerstone in the management of heart failure, particularly in patients with DCM. However, identifying patients who will benefit the most from CRT remains challenging. Speckle tracking echocardiography (STE) has garnered attention as a non-invasive imaging modality that allows for the quantitative assessment of myocardial mechanics, offering insights into LV function beyond traditional echocardiographic parameters. This comprehensive review explores the role of STE in guiding patient selection and optimizing outcomes in CRT for DCM. By assessing parameters such as LV strain, strain rate, and dyssynchrony, STE enables a more precise evaluation of myocardial function and mechanical dyssynchrony, aiding in the identification of patients who are most likely to benefit from CRT. Furthermore, STE provides valuable prognostic information and facilitates post-CRT optimization by guiding lead placement and assessing response to therapy. Through an integration of STE with CRT, clinicians can enhance patient selection, improve procedural success rates, and ultimately, optimize clinical outcomes in patients with DCM. This review underscores the pivotal role of STE in advancing personalized management strategies for DCM patients undergoing CRT.
PubMed: 38893704
DOI: 10.3390/diagnostics14111178 -
Diagnostics (Basel, Switzerland) Jun 2024The benefit of prophylactic implantable cardioverter defibrillators (ICDs) in patients with severe systolic dysfunction of non-ischemic origin is still unclear, and the...
Right Bundle Branch Block Predicts Appropriate Implantable Cardioverter Defibrillator Therapies in Patients with Non-Ischemic Dilated Cardiomyopathy and a Prophylactic Implantable Cardioverter Defibrillator.
The benefit of prophylactic implantable cardioverter defibrillators (ICDs) in patients with severe systolic dysfunction of non-ischemic origin is still unclear, and the identification of patients at risk for sudden cardiac death remains a major challenge. We retrospectively reviewed all consecutive patients with non-ischemic dilated cardiomyopathy (NICM) who underwent prophylactic ICD implantation between 2008 and 2020 in two tertiary centers. Our main goal was to identify the predictors of appropriate ICD therapies (anti-tachycardia pacing [ATP] and/or shocks) in this cohort of patients. A total of 224 patients were included. After a median follow-up of 51 months, 61 patients (27.2%) required appropriate ICD therapies. Patients with appropriate ICD therapies were more frequently men (87% vs. 69%, = 0.006), of younger age (59 years, (53-65) vs. 64 years, (57-70); = 0.02), showed more right bundle branch blocks (RBBBs) (15% vs. 4%, = 0.007) and less left bundle branch blocks (LBBBs) (26% vs. 47%, = 0.005) in the ECG, and had higher left ventricular end-diastolic (100 mL/m, (90-117) vs. 86, (71-110); = 0.011) and systolic volumes (72 mL/m, (59-87) vs. 61, (47-81), = 0.05). In a multivariate competing-risks regression analysis, RBBB (HR 2.26, CI 95% 1.02-4.98, = 0.043) was identified as an independent predictor of appropriate ICD therapies. RBBBs may help to identify patients with NICM at high risk of ventricular arrhythmias and requiring ICD intervention.
PubMed: 38893699
DOI: 10.3390/diagnostics14111173 -
Journal of Clinical Medicine May 2024-related dilated cardiomyopathy (-DCM) caused by mutations in the lamin A/C gene () is one of the most common forms of hereditary DCM. Due to the high risk of mutation...
-related dilated cardiomyopathy (-DCM) caused by mutations in the lamin A/C gene () is one of the most common forms of hereditary DCM. Due to the high risk of mutation transmission to offspring and the high incidence of ventricular arrhythmia and sudden death even before the onset of heart failure symptoms, it is very important to identify -mutation carriers. However, many relatives of -DCM patients do not report to specialized centers for clinical or genetic screening. Therefore, an easily available tool to identify at-risk subjects is needed. We compared two cohorts of young, asymptomatic relatives of DCM patients who reported for screening: 29 mutation carriers and 43 individuals from the control group. Receiver operating characteristic (ROC) curves for potential indicators of mutation carriership status were analyzed. PR interval, N-terminal pro-B-type natriuretic peptide (NT-proBNP), and high-sensitivity cardiac troponin T (hscTnT) serum levels were higher in the mutation carrier cohort. Neither group differed significantly with regard to creatinine concentration or left ventricular ejection fraction. The best mutation carriership discriminator was hscTnT level with an optimal cut-off value at 5.5 ng/L, for which sensitivity and specificity were 86% and 93%, respectively. The median hscTnT level was 11.0 ng/L in mutation carriers vs. <3.0 ng/L in the control group, < 0.001. Wherever access to genetic testing is limited, mutation carriership status can be assessed reliably using the hscTnT assay. Among young symptomless relatives of -DCM patients, a hscTnT level >5.5 ng/L strongly suggests mutation carriers.
PubMed: 38892874
DOI: 10.3390/jcm13113164 -
International Journal of Molecular... Jun 2024Arrhythmogenic cardiomyopathy (ACM) is an inherited myocardial disease at risk of sudden death. Genetic testing impacts greatly in ACM diagnosis, but gene-disease...
Arrhythmogenic cardiomyopathy (ACM) is an inherited myocardial disease at risk of sudden death. Genetic testing impacts greatly in ACM diagnosis, but gene-disease associations have yet to be determined for the increasing number of genes included in clinical panels. Genetic variants evaluation was undertaken for the most relevant non-desmosomal disease genes. We retrospectively studied 320 unrelated Italian ACM patients, including 243 cases with predominant right-ventricular (ARVC) and 77 cases with predominant left-ventricular (ALVC) involvement, who did not carry pathogenic/likely pathogenic (P/LP) variants in desmosome-coding genes. The aim was to assess rare genetic variants in transmembrane protein 43 (), desmin (), phospholamban (), filamin c (), cadherin 2 (), and tight junction protein 1 (), based on current adjudication guidelines and reappraisal on reported literature data. Thirty-five rare genetic variants, including 23 (64%) P/LP, were identified in 39 patients (16/243 ARVC; 23/77 ALVC): 22 , 9 , 2 , and 2 . No P/LP variants were found in and genes. Gene-based burden analysis, including P/LP variants reported in literature, showed significant enrichment for (3.79-fold), (10.31-fold), (117.8-fold) and (107-fold). A non-desmosomal rare genetic variant is found in a minority of ARVC patients but in about one third of ALVC patients; as such, clinical decision-making should be driven by genes with robust evidence. More than two thirds of non-desmosomal P/LP variants occur in FLNC.
Topics: Humans; Arrhythmogenic Right Ventricular Dysplasia; Female; Male; Adult; Middle Aged; Membrane Proteins; Cadherins; Desmosomes; Genetic Predisposition to Disease; Genetic Variation; Filamins; Retrospective Studies; Italy; Calcium-Binding Proteins; Antigens, CD
PubMed: 38892455
DOI: 10.3390/ijms25116267 -
International Journal of Molecular... Jun 2024Sarcospan (SSPN) is a 25-kDa transmembrane protein that is broadly expressed at the cell surface of many tissues, including, but not limited to, the myofibers from...
Sarcospan (SSPN) is a 25-kDa transmembrane protein that is broadly expressed at the cell surface of many tissues, including, but not limited to, the myofibers from skeletal and smooth muscles, cardiomyocytes, adipocytes, kidney epithelial cells, and neurons. SSPN is a core component of the dystrophin-glycoprotein complex (DGC) that links the intracellular actin cytoskeleton with the extracellular matrix. It is also associated with integrin α7β1, the predominant integrin expressed in skeletal muscle. As a tetraspanin-like protein with four transmembrane spanning domains, SSPN functions as a scaffold to facilitate protein-protein interactions at the cell membrane. Duchenne muscular dystrophy, Becker muscular dystrophy, and X-linked dilated cardiomyopathy are caused by the loss of dystrophin at the muscle cell surface and a concomitant loss of the entire DGC, including SSPN. SSPN overexpression ameliorates Duchenne muscular dystrophy in the murine model, which supports SSPN being a viable therapeutic target. Other rescue studies support SSPN as a biomarker for the proper assembly and membrane expression of the DGC. Highly specific and robust antibodies to SSPN are needed for basic research on the molecular mechanisms of SSPN rescue, pre-clinical studies, and biomarker evaluations in human samples. The development of SSPN antibodies is challenged by the presence of its four transmembrane domains and limited antigenic epitopes. To address the significant barrier presented by limited commercially available antibodies, we aimed to generate a panel of robust SSPN-specific antibodies that can serve as a resource for the research community. We created antibodies to three SSPN protein epitopes, including the intracellular N- and C-termini as well as the large extracellular loop (LEL) between transmembrane domains 3 and 4. We developed a panel of rabbit antibodies (poly- and monoclonal) against an N-terminal peptide fragment of SSPN. We used several assays to show that the rabbit antibodies recognize mouse SSPN with a high functional affinity and specificity. We developed mouse monoclonal antibodies against the C-terminal peptide and the large extracellular loop of human SSPN. These antibodies are superior to commercially available antibodies and outperform them in various applications, including immunoblotting, indirect immunofluorescence analysis, immunoprecipitation, and an ELISA. These newly developed antibodies will significantly improve the quality and ease of SSPN detection for basic and translational research.
Topics: Animals; Humans; Mice; Dystrophin; Integrins; Membrane Proteins; Muscular Dystrophy, Duchenne; Translational Research, Biomedical
PubMed: 38892308
DOI: 10.3390/ijms25116121 -
International Journal of Molecular... May 2024Myocarditis is characterized by an influx of inflammatory cells, predominantly of myeloid lineage. The progression of myocarditis to a dilated cardiomyopathy is markedly...
Myocarditis is characterized by an influx of inflammatory cells, predominantly of myeloid lineage. The progression of myocarditis to a dilated cardiomyopathy is markedly influenced by TGF-β signalling. Here, we investigate the role of TGF-β signalling in inflammatory cardiac macrophages in the development of myocarditis and post-inflammatory fibrosis. Experimental autoimmune myocarditis (EAM) was induced in the × × transgenic mice showing impaired TGF-β signalling in the myeloid lineage and the × control mice. In EAM, immunization led to acute myocarditis on day 21, followed by cardiac fibrosis on day 40. Both strains showed a similar severity of myocarditis and the extent of cardiac fibrosis. On day 21 of EAM, an increase in cardiac inflammatory macrophages was observed in both strains. These cells were sorted and analysed for differential gene expression using whole-genome transcriptomics. The analysis revealed activation and regulation of the inflammatory response, particularly the production of both pro-inflammatory and anti-inflammatory cytokines and cytokine receptors as TGF-β-dependent processes. The analysis of selected cytokines produced by bone marrow-derived macrophages confirmed their suppressed secretion. In conclusion, our findings highlight the regulatory role of TGF-β signalling in cytokine production within inflammatory cardiac macrophages during myocarditis.
Topics: Animals; Myocarditis; Transforming Growth Factor beta; Mice; Macrophages; Signal Transduction; Autoimmune Diseases; Cytokines; Mice, Transgenic; Disease Models, Animal; Myocardium; Fibrosis; Male
PubMed: 38891767
DOI: 10.3390/ijms25115579 -
Cells May 2024The transmembrane proteoglycan syndecan-4 is known to be involved in the hypertrophic response to pressure overload. Although multiple downstream signaling pathways have...
The transmembrane proteoglycan syndecan-4 is known to be involved in the hypertrophic response to pressure overload. Although multiple downstream signaling pathways have been found to be involved in this response in a syndecan-4-dependent manner, there are likely more signaling components involved. As part of a larger syndecan-4 interactome screening, we have previously identified MLP as a binding partner to the cytoplasmic tail of syndecan-4. Interestingly, many human MLP mutations have been found in patients with hypertrophic (HCM) and dilated cardiomyopathy (DCM). To gain deeper insight into the role of the syndecan-4-MLP interaction and its potential involvement in MLP-associated cardiomyopathy, we have here investigated the syndecan-4-MLP interaction in primary adult rat cardiomyocytes and the H9c2 cell line. The binding of syndecan-4 and MLP was analyzed in total lysates and subcellular fractions of primary adult rat cardiomyocytes, and baseline and differentiated H9c2 cells by immunoprecipitation. MLP and syndecan-4 localization were determined by confocal microscopy, and MLP oligomerization was determined by immunoblotting under native conditions. Syndecan-4-MLP binding, as well as MLP self-association, were also analyzed by ELISA and peptide arrays. Our results showed that MLP-WT and syndecan-4 co-localized in many subcellular compartments; however, their binding was only detected in nuclear-enriched fractions of isolated adult cardiomyocytes. In vitro, syndecan-4 bound to MLP at three sites, and this binding was reduced in some HCM-associated MLP mutations. While MLP and syndecan-4 also co-localized in many subcellular fractions of H9c2 cells, these proteins did not bind at baseline or after differentiation into cardiomyocyte-resembling cells. Independently of syndecan-4, mutated MLP proteins had an altered subcellular localization in H9c2 cells, compared to MLP-WT. The DCM- and HCM-associated MLP mutations, W4R, L44P, C58G, R64C, Y66C, K69R, G72R, and Q91L, affected the oligomerization of MLP with an increase in monomeric at the expense of trimeric and tetrameric recombinant MLP protein. Lastly, two crucial sites for MLP self-association were identified, which were reduced in most MLP mutations. Our data indicate that the syndecan-4-MLP interaction was present in nuclear-enriched fractions of isolated adult cardiomyocytes and that this interaction was disrupted by some HCM-associated MLP mutations. MLP mutations were also linked to changes in MLP oligomerization and self-association, which may be essential for its interaction with syndecan-4 and a critical molecular mechanism of MLP-associated cardiomyopathy.
Topics: Syndecan-4; Myocytes, Cardiac; Animals; Rats; Protein Binding; Cell Line; Humans
PubMed: 38891079
DOI: 10.3390/cells13110947 -
Cells May 2024Intracellular cargo delivery via distinct transport routes relies on vesicle carriers. A key trafficking route distributes cargo taken up by clathrin-mediated...
Intracellular cargo delivery via distinct transport routes relies on vesicle carriers. A key trafficking route distributes cargo taken up by clathrin-mediated endocytosis (CME) via early endosomes. The highly dynamic nature of the endosome network presents a challenge for its quantitative analysis, and theoretical modelling approaches can assist in elucidating the organization of the endosome trafficking system. Here, we introduce a new computational modelling approach for assessment of endosome distributions. We employed a model of induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) with inherited mutations causing dilated cardiomyopathy (DCM). In this model, vesicle distribution is defective due to impaired CME-dependent signaling, resulting in plasma membrane-localized early endosomes. We recapitulated this in iPSC-CMs carrying two different mutations, TPM1-L185F and TnT-R141W (MUT), using 3D confocal imaging as well as super-resolution STED microscopy. We computed scaled distance distributions of EEA1-positive vesicles based on a spherical approximation of the cell. Employing this approach, 3D spherical modelling identified a bi-modal segregation of early endosome populations in MUT iPSC-CMs, compared to WT controls. Moreover, spherical modelling confirmed reversion of the bi-modal vesicle localization in RhoA II-treated MUT iPSC-CMs. This reflects restored, homogeneous distribution of early endosomes within MUT iPSC-CMs following rescue of CME-dependent signaling via RhoA II-dependent RhoA activation. Overall, our approach enables assessment of early endosome distribution in cell-based disease models. This new method may provide further insight into the dynamics of endosome networks in different physiological scenarios.
Topics: Humans; Induced Pluripotent Stem Cells; Endosomes; Myocytes, Cardiac; Endocytosis; Mutation; Computer Simulation; rhoA GTP-Binding Protein; Cardiomyopathies; Imaging, Three-Dimensional; Cardiomyopathy, Dilated; Models, Biological; Tropomyosin
PubMed: 38891055
DOI: 10.3390/cells13110923 -
PloS One 2024Obg-like ATPase 1 (OLA1) protein has GTP and ATP hydrolyzing activities and is important for cellular growth and survival. The human OLA1 gene maps to chromosome 2...
Obg-like ATPase 1 (OLA1) protein has GTP and ATP hydrolyzing activities and is important for cellular growth and survival. The human OLA1 gene maps to chromosome 2 (locus 2q31.1), near Titin (TTN), which is associated with familial dilated cardiomyopathy (DCM). In this study, we found that expression of OLA1 was significantly downregulated in failing human heart tissue (HF) compared to non-failing hearts (NF). Using the Sanger sequencing method, we characterized the human OLA1 gene and screened for mutations in the OLA1 gene in patients with failing and non-failing hearts. Among failing and non-failing heart patients, we found 15 different mutations in the OLA1 gene, including two transversions, one substitution, one deletion, and eleven transitions. All mutations were intronic except for a non-synonymous 5144A>G, resulting in 254Tyr>Cys in exon 8 of the OLA1 gene. Furthermore, haplotype analysis of these mutations revealed that these single nucleotide polymorphisms (SNPs) are linked to each other, resulting in disease-specific haplotypes. Additionally, to screen the 254Tyr>Cys point mutation, we developed a cost-effective, rapid genetic screening PCR test that can differentiate between homozygous (AA and GG) and heterozygous (A/G) genotypes. Our results demonstrate that this PCR test can effectively screen for OLA1 mutation-associated cardiomyopathy in human patients using easily accessible cells or tissues, such as blood cells. These findings have important implications for the diagnosis and treatment of cardiomyopathy.
Topics: Humans; Heart Failure; Polymorphism, Single Nucleotide; Male; Female; Haplotypes; Polymerase Chain Reaction; Cardiomyopathy, Dilated; Middle Aged; Adult; Genetic Testing; Mutation; Adenosine Triphosphatases
PubMed: 38889130
DOI: 10.1371/journal.pone.0293105