Phenotype and Clinical Outcomes in Desmin-Related Arrhythmogenic Cardiomyopathy.

BACKGROUND: Desmin (DES) pathogenic variants cause a small proportion of arrhythmogenic cardiomyopathy (ACM). Outcomes data on DES-related ACM are scarce. OBJECTIVES: This study sought to provide information on the clinical phenotype and outcomes of patients with ACM caused by pathogenic variants of the DES gene in a multicenter cohort. METHODS: We collected phenotypic and outcomes data from 16 families with DES-related ACM from 10 European centers. We assessed in vitro DES aggregates. Major cardiac events were compared to historical controls with lamin A/C truncating variant (LMNA-tv) and filament C truncating variant (FLNC-tv) ACM. RESULTS: Of 82 patients (54% males, median age: 36 years), 11 experienced sudden cardiac death (SCD) (n = 7) or heart failure death (HFd)/heart transplantation (HTx) (n = 4) before clinical evaluation. Among 68 survivors, 59 (86%) presented signs of cardiomyopathy, with left ventricular (LV) dominant (50%) or biventricular (34%) disease. Mean LV ejection fraction was 51% ± 13%; 36 of 53 had late gadolinium enhancement (ring-like pattern in 49%). During a median of 6.73 years (Q1-Q3: 3.55-9.52 years), the composite endpoint (sustained ventricular tachycardia, aborted SCD, implantable cardioverter-defibrillator therapy, SCD, HFd, and HTx) was achieved in 15 additional patients with HFd/HTx (n = 5) and SCD/aborted SCD/implantable cardioverter-defibrillator therapy/sustained ventricular tachycardia (n = 10). Male sex (P = 0.004), nonsustained ventricular tachycardia (P = 0.017) and LV ejection fraction ≤50% (P = 0.012) were associated with the composite endpoint. Males with DES variants had similar outcomes to historical FLNC-tv and LMNA-tv controls. However, females showed better outcomes than those with LMNA-tv. In vitro experiments showed the characteristic finding of DES aggregates in 7 of 12 variants. CONCLUSIONS: DES ACM is associated with poor outcomes which can be predicted with potentially successful treatments, underscoring the importance of familial evaluation and genetic studies to identify at risk individuals.

Cardiomyopathy related desmocollin-2 prodomain variants affect the intracellular cadherin transport and processing.

Background: Arrhythmogenic cardiomyopathy can be caused by genetic variants in desmosomal cadherins. Since cardiac desmosomal cadherins are crucial for cell-cell-adhesion, their correct localization at the plasma membrane is essential. Methods: Nine desmocollin-2 variants at five positions from various public genetic databases (p.D30N, p.V52A/I, p.G77V/D/S, p.V79G, p.I96V/T) and three additional conserved positions (p.C32, p.C57, p.F71) within the prodomain were investigated in vitro using confocal microscopy. Model variants (p.C32A/S, p.V52G/L, p.C57A/S, p.F71Y/A/S, p.V79A/I/L, p.I96l/A) were generated to investigate the impact of specific amino acids. Results: We revealed that all analyzed positions in the prodomain are critical for the intracellular transport. However, the variants p.D30N, p.V52A/I and p.I96V listed in genetic databases do not disturb the intracellular transport revealing that the loss of these canonical sequences may be compensated. Conclusion: As disease-related homozygous truncating desmocollin-2 variants lacking the transmembrane domain are not localized at the plasma membrane, we predict that some of the investigated prodomain variants may be relevant in the context of arrhythmogenic cardiomyopathy due to disturbed intracellular transport.

The Consideration of Pseudoxanthoma Elasticum as a Progeria Syndrome.

BACKGROUND: Pseudoxanthoma elasticum (PXE) is a rare autosomal recessive disorder caused by mutations in the ATP-binding cassette sub-family C member 6 (ABCC6) gene. Patients with PXE show molecular and clinical characteristics of known premature aging syndromes, such as Hutchinson-Gilford progeria syndrome (HGPS). Nevertheless, PXE has only barely been discussed against the background of premature aging, although a detailed characterization of aging processes in PXE could contribute to a better understanding of its pathogenesis. Thus, this study was performed to evaluate whether relevant factors which are known to play a role in accelerated aging processes in HGPS pathogenesis are also dysregulated in PXE. METHODS: Primary human dermal fibroblasts from healthy donors (n = 3) and PXE patients (n = 3) and were cultivated under different culture conditions as our previous studies point towards effects of nutrient depletion on PXE phenotype. Gene expression of lamin A, lamin C, nucleolin, farnesyltransferase and zinc metallopeptidase STE24 were determined by quantitative real-time polymerase chain reaction. Additionally, protein levels of lamin A, C and nucleolin were evaluated by immunofluorescence and the telomere length was analyzed. RESULTS: We could show a significant decrease of lamin A and C gene expression in PXE fibroblasts under nutrient depletion compared to controls. The gene expression of progerin and farnesyltransferase showed a significant increase in PXE fibroblasts when cultivated in 10% fetal calf serum (FCS) compared to controls. Immunofluorescence microscopy of lamin A/C and nucleolin and mRNA expression of zinc metallopeptidase STE24 and nucleolin showed no significant changes in any case. The determination of the relative telomere length showed significantly longer telomeres for PXE fibroblasts compared to controls when cultivated in 10% FCS. CONCLUSIONS: These data indicate that PXE fibroblasts possibly undergo a kind of senescence which is independent of telomere damage and not triggered by defects of the nuclear envelope or nucleoli deformation.

Spatial transcriptomics unveils ZBTB11 as a regulator of cardiomyocyte degeneration in arrhythmogenic cardiomyopathy.

AIMS: Arrhythmogenic cardiomyopathy (ACM) is an inherited cardiac disorder that is characterized by progressive loss of myocardium that is replaced by fibro-fatty cells, arrhythmias, and sudden cardiac death. While myocardial degeneration and fibro-fatty replacement occur in specific locations, the underlying molecular changes remain poorly characterized. Here, we aim to delineate local changes in gene expression to identify new genes and pathways that are relevant for specific remodelling processes occurring during ACM. METHODS AND RESULTS: Using Tomo-Seq, genome-wide transcriptional profiling with high spatial resolution, we created transmural epicardial-to-endocardial gene expression atlases of explanted ACM hearts to gain molecular insights into disease-driving processes. This enabled us to link gene expression profiles to the different regional remodelling responses and allowed us to identify genes that are potentially relevant for disease progression. In doing so, we identified distinct gene expression profiles marking regions of cardiomyocyte degeneration and fibro-fatty remodelling and revealed Zinc finger and BTB domain-containing protein 11 (ZBTB11) to be specifically enriched at sites of active fibro-fatty replacement of myocardium. Immunohistochemistry indicated ZBTB11 to be induced in cardiomyocytes flanking fibro-fatty areas, which could be confirmed in multiple cardiomyopathy patients. Forced overexpression of ZBTB11 induced autophagy and cell death-related gene programmes in human cardiomyocytes, leading to increased apoptosis. CONCLUSION: Our study shows the power of Tomo-Seq to unveil new molecular mechanisms in human cardiomyopathy and uncovers ZBTB11 as a novel driver of cardiomyocyte loss.

ROD2 domain filamin C missense mutations exhibit a distinctive cardiac phenotype with restrictive/hypertrophic cardiomyopathy and saw-tooth myocardium.

INTRODUCTION AND OBJECTIVES: Missense mutations in the filamin C (FLNC) gene have been reported as cause of inherited cardiomyopathy. Knowledge of the pathogenicity and genotype-phenotype correlation remains scarce. Our aim was to describe a distinctive cardiac phenotype related to rare missense FLNC variants in the ROD2 domain. METHODS: We recruited 21 unrelated families genetically evaluated because of hypertrophic cardiomyopathy (HCM)/restrictive cardiomyopathy (RCM) phenotype carrying rare missense variants in the ROD2 domain of FLNC (FLNC-mRod2). Carriers underwent advanced cardiac imaging and genetic cascade screening. Myocardial tissue from 3 explanted hearts of a missense FLNC carrier was histologically analyzed and compared with an FLNC-truncating variant heart sample and a healthy control. Plasmids independently containing 3 FLNC missense variants were transfected and analyzed using confocal microscopy. RESULTS: Eleven families (52%) with 20 assessed individuals (37 [23.7-52.7]) years showed 15 cases with a cardiac phenotype consisting of an overlap of HCM-RCM and left ventricular hypertrabeculation (saw-tooth appearance). During a median follow-up of 6.49 years, they presented with advanced heart failure: 16 (80%) diastolic dysfunction, 3 heart transplants, 3 heart failure deaths) and absence of cardiac conduction disturbances or skeletal myopathy. A total of 6 families had moderate genotype-phenotype segregation, and the remaining were de novo variants. Differential extracellular matrix remodeling and FLNC distribution among cardiomyocytes were confirmed on histology. HT1080 and H9c2 cells did not reveal cytoplasmic aggregation of mutant FLNC. CONCLUSIONS: FLNC-mRod2 variants show a high prevalence of an overlapped phenotype comprising RCM, HCM and deep hypertrabeculation with saw-tooth appearance and distinctive cardiac histopathological remodeling.

The N-Terminal Part of the 1A Domain of Desmin Is a Hot Spot Region for Putative Pathogenic DES Mutations Affecting Filament Assembly.

Desmin is the major intermediate filament protein of all three muscle cell types, and connects different cell organelles and multi-protein complexes such as the cardiac desmosomes. Several pathogenic mutations in the DES gene cause different skeletal and cardiac myopathies. However, the significance of the majority of DES missense variants is currently unknown, since functional data are lacking. To determine whether desmin missense mutations within the highly conserved 1A coil domain cause a filament assembly defect, we generated a set of variants with unknown significance and systematically analyzed the filament assembly using confocal microscopy in transfected SW-13, H9c2 cells and cardiomyocytes derived from induced pluripotent stem cells. We found that mutations in the N-terminal part of the 1A coil domain affect filament assembly, leading to cytoplasmic desmin aggregation. In contrast, mutant desmin in the C-terminal part of the 1A coil domain forms filamentous structures comparable to wild-type desmin. Our findings suggest that the N-terminal part of the 1A coil domain is a hot spot for pathogenic desmin mutations, which affect desmin filament assembly. This study may have relevance for the genetic counselling of patients carrying variants in the 1A coil domain of the DES gene.

Altered Expression of TMEM43 Causes Abnormal Cardiac Structure and Function in Zebrafish.

Arrhythmogenic cardiomyopathy (ACM) is an inherited heart muscle disease caused by heterozygous missense mutations within the gene encoding for the nuclear envelope protein transmembrane protein 43 (TMEM43). The disease is characterized by myocyte loss and fibro-fatty replacement, leading to life-threatening ventricular arrhythmias and sudden cardiac death. However, the role of TMEM43 in the pathogenesis of ACM remains poorly understood. In this study, we generated cardiomyocyte-restricted transgenic zebrafish lines that overexpress eGFP-linked full-length human wild-type (WT) TMEM43 and two genetic variants (c.1073C>T, p.S358L; c.332C>T, p.P111L) using the Tol2-system. Overexpression of WT and p.P111L-mutant TMEM43 was associated with transcriptional activation of the mTOR pathway and ribosome biogenesis, and resulted in enlarged hearts with cardiomyocyte hypertrophy. Intriguingly, mutant p.S358L TMEM43 was found to be unstable and partially redistributed into the cytoplasm in embryonic and adult hearts. Moreover, both TMEM43 variants displayed cardiac morphological defects at juvenile stages and ultrastructural changes within the myocardium, accompanied by dysregulated gene expression profiles in adulthood. Finally, CRISPR/Cas9 mutants demonstrated an age-dependent cardiac phenotype characterized by heart enlargement in adulthood. In conclusion, our findings suggest ultrastructural remodeling and transcriptomic alterations underlying the development of structural and functional cardiac defects in TMEM43-associated cardiomyopathy.

Compound Heterozygous FKTN Variants in a Patient with Dilated Cardiomyopathy Led to an Aberrant α-Dystroglycan Pattern.

Fukutin encoded by FKTN is a ribitol 5-phosphate transferase involved in glycosylation of α-dystroglycan. It is known that mutations in FKTN affect the glycosylation of α-dystroglycan, leading to a dystroglycanopathy. Dystroglycanopathies are a group of syndromes with a broad clinical spectrum including dilated cardiomyopathy and muscular dystrophy. In this study, we reported the case of a patient with muscular dystrophy, early onset dilated cardiomyopathy, and elevated creatine kinase levels who was a carrier of the compound heterozygous variants p.Ser299Arg and p.Asn442Ser in FKTN. Our work showed that compound heterozygous mutations in FKTN lead to a loss of fully glycosylated α-dystroglycan and result in cardiomyopathy and end-stage heart failure at a young age.

Genetic Insights into Primary Restrictive Cardiomyopathy.

Restrictive cardiomyopathy is a rare cardiac disease causing severe diastolic dysfunction, ventricular stiffness and dilated atria. In consequence, it induces heart failure often with preserved ejection fraction and is associated with a high mortality. Since it is a poor clinical prognosis, patients with restrictive cardiomyopathy frequently require heart transplantation. Genetic as well as non-genetic factors contribute to restrictive cardiomyopathy and a significant portion of cases are of unknown etiology. However, the genetic forms of restrictive cardiomyopathy and the involved molecular pathomechanisms are only partially understood. In this review, we summarize the current knowledge about primary genetic restrictive cardiomyopathy and describe its genetic landscape, which might be of interest for geneticists as well as for cardiologists.

A detailed protocol for expression, purification, and activity determination of recombinant SaCas9.

Recombinant SaCas9 is useful for a broad range of applications in the context of genome editing, especially when the specific protospacer adjacent motifs of other Cas9 derivatives are missing. Here, we describe a detailed protocol for the expression and purification of recombinant SaCas9. We detail the main steps for immobilized metal affinity chromatography and size exclusion chromatography. In addition, we present an assay for activity determination of SaCas9. Active SaCas9 can be purified in a week by using this protocol.

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

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.

Insights Into Genetics and Pathophysiology of Arrhythmogenic Cardiomyopathy.

PURPOSE OF REVIEW: Arrhythmogenic cardiomyopathy (ACM) is a genetic disease characterized by life-threatening ventricular arrhythmias and sudden cardiac death (SCD) in apparently healthy young adults. Mutations in genes encoding for cellular junctions can be found in about half of the patients. However, disease onset and severity, risk of arrhythmias, and outcome are highly variable and drug-targeted treatment is currently unavailable. RECENT FINDINGS: This review focuses on advances in clinical risk stratification, genetic etiology, and pathophysiological concepts. The desmosome is the central part of the disease, but other intercalated disc and associated structural proteins not only broaden the genetic spectrum but also provide novel molecular and cellular insights into the pathogenesis of ACM. Signaling pathways and the role of inflammation will be discussed and targets for novel therapeutic approaches outlined. Genetic discoveries and experimental-driven preclinical research contributed significantly to the understanding of ACM towards mutation- and pathway-specific personalized medicine.

The Double Mutation DSG2-p.S363X and TBX20-p.D278X Is Associated with Left Ventricular Non-Compaction Cardiomyopathy: Case Report.

Left ventricular non-compaction cardiomyopathy (LVNC) is a rare heart disease, with or without left ventricular dysfunction, which is characterized by a two-layer structure of the myocardium and an increased number of trabeculae. The study of familial forms of LVNC is helpful for risk prediction and genetic counseling of relatives. Here, we present a family consisting of three members with LVNC. Using a next-generation sequencing approach a combination of two (likely) pathogenic nonsense mutations DSG2-p.S363X and TBX20-p.D278X was identified in all three patients. TBX20 encodes the cardiac T-box transcription factor 20. DSG2 encodes desmoglein-2, which is part of the cardiac desmosomes and belongs to the cadherin family. Since the identified nonsense variant (DSG2-p.S363X) is localized in the extracellular domain of DSG2, we performed in vitro cell transfection experiments. These experiments revealed the absence of truncated DSG2 at the plasma membrane, supporting the pathogenic relevance of DSG2-p.S363X. In conclusion, we suggest that in the future, these findings might be helpful for genetic screening and counseling of patients with LVNC.

The Combined Human Genotype of Truncating TTN and RBM20 Mutations Is Associated with Severe and Early Onset of Dilated Cardiomyopathy.

A major cause of heart failure is cardiomyopathies, with dilated cardiomyopathy (DCM) as the most common form. Over 40 genes are linked to DCM, among them TTN and RBM20. Next Generation Sequencing in clinical DCM cohorts revealed truncating variants in TTN (TTNtv), accounting for up to 25% of familial DCM cases. Mutations in the cardiac splicing factor RNA binding motif protein 20 (RBM20) are also known to be associated with severe cardiomyopathies. TTN is one of the major RBM20 splicing targets. Most of the pathogenic RBM20 mutations are localized in the highly conserved arginine serine rich domain (RS), leading to a cytoplasmic mislocalization of mutant RBM20. Here, we present a patient with an early onset DCM carrying a combination of (likely) pathogenic TTN and RBM20 mutations. We show that the splicing of RBM20 target genes is affected in the mutation carrier. Furthermore, we reveal RBM20 haploinsufficiency presumably caused by the frameshift mutation in RBM20.

Special Issue "Cardiovascular Genetics".

Since the beginnings of cardiovascular genetics, it became evident in thousands of clinical cases that many cardiomyopathies, channelopathies, aortopathies as well as complex multifactorial diseases such as coronary artery disease, atherosclerosis or atrial fibrillation (AF) have a genetic etiology [...].

Hemi- and Homozygous Loss-of-Function Mutations in DSG2 (Desmoglein-2) Cause Recessive Arrhythmogenic Cardiomyopathy with an Early Onset.

About 50% of patients with arrhythmogenic cardiomyopathy (ACM) carry a pathogenic or likely pathogenic mutation in the desmosomal genes. However, there is a significant number of patients without positive familial anamnesis. Therefore, the molecular reasons for ACM in these patients are frequently unknown and a genetic contribution might be underestimated. Here, we used a next-generation sequencing (NGS) approach and in addition single nucleotide polymor-phism (SNP) arrays for the genetic analysis of two independent index patients without familial medical history. Of note, this genetic strategy revealed a homozygous splice site mutation (DSG2-c.378+1G>T) in the first patient and a nonsense mutation (DSG2-p.L772X) in combination with a large deletion in DSG2 in the second one. In conclusion, a recessive inheritance pattern is likely for both cases, which might contribute to the hidden medical history in both families. This is the first report about these novel loss-of-function mutations in DSG2 that have not been previously identi-fied. Therefore, we suggest performing deep genetic analyses using NGS in combination with SNP arrays also for ACM index patients without obvious familial medical history. In the future, this finding might has relevance for the genetic counseling of similar cases.

The Desmin (DES) Mutation p.A337P Is Associated with Left-Ventricular Non-Compaction Cardiomyopathy.

Here, we present a small Russian family, where the index patient received a diagnosis of left-ventricular non-compaction cardiomyopathy (LVNC) in combination with a skeletal myopathy. Clinical follow-up analysis revealed a LVNC phenotype also in her son. Therefore, we applied a broad next-generation sequencing gene panel approach for the identification of the underlying mutation. Interestingly, DES-p.A337P was identified in the genomes of both patients, whereas only the index patient carried DSP-p.L1348X. DES encodes the muscle-specific intermediate filament protein desmin and DSP encodes desmoplakin, which is a cytolinker protein connecting desmosomes with the intermediate filaments. Because the majority of DES mutations cause severe filament assembly defects and because this mutation was found in both affected patients, we analyzed this DES mutation in vitro by cell transfection experiments in combination with confocal microscopy. Of note, desmin-p.A337P forms cytoplasmic aggregates in transfected SW-13 cells and in cardiomyocytes derived from induced pluripotent stem cells underlining its pathogenicity. In conclusion, we suggest including the DES gene in the genetic analysis for LVNC patients in the future, especially if clinical involvement of the skeletal muscle is present.

Functional characterization of novel alpha-helical rod domain desmin (DES) pathogenic variants associated with dilated cardiomyopathy, atrioventricular block and a risk for sudden cardiac death.

BACKGROUND: Desmin is the major intermediate filament (IF) protein in human heart and skeletal muscle. So-called 'desminopathies' are disorders due to pathogenic variants in the DES gene and are associated with skeletal myopathies and/or various types of cardiomyopathies. So far, only a limited number of DES pathogenic variants have been identified and functionally characterized. METHODS AND RESULTS: Using a Sanger- and next generation sequencing (NGS) approach in patients with various types of cardiomyopathies, we identified two novel, non-synonymous missense DES variants: p.(Ile402Thr) and p.(Glu410Lys). Mutation carriers developed dilated (DCM) or arrhythmogenic cardiomyopathy (ACM), and cardiac conduction disease, leading to spare out the exercise-induced polymorphic ventricular tachycardia; we moved this variant to data in brief. To investigate the functional impact of these four DES variants, transfection experiments using SW-13 and H9c2 cells with native and mutant desmin were performed and filament assembly was analyzed by confocal microscopy. The DES_p.(Ile402Thr) and DES_p.(Glu410Lys) cells showed filament assembly defects forming cytoplasmic desmin aggregates. Furthermore, immunohistochemical and ultrastructural analysis of myocardial tissue from mutation carriers with the DES_p.(Glu410Lys) pathogenic variant supported the in vitro results. CONCLUSIONS: Our in vitro results supported the classification of DES_p.(Ile402Thr) and DES_p.(Glu410Lys) as novel pathogenic variants and demonstrated that the cardiac phenotypes associated with DES variants are diverse and cell culture experiments improve in silico analysis and genetic counseling because the pathogenicity of a variant can be clarified.

The Novel Desmin Variant p.Leu115Ile Is Associated With a Unique Form of Biventricular Arrhythmogenic Cardiomyopathy.

BACKGROUND: Arrhythmogenic cardiomyopathy (AC) is a heritable myocardial disorder and a major cause of sudden cardiac death. It is typically caused by mutations in desmosomal genes. Desmin gene (DES) variants have been previously reported in AC but with insufficient evidence to support their pathogenicity. METHODS: We aimed to assess a large AC patient cohort for DES mutations and describe a unique phenotype associated with a recurring variant in three families. A cohort of 138 probands with a diagnosis of AC and no identifiable desmosomal gene mutations were prospectively screened by whole-exome sequencing. RESULTS: A single DES variant (p.Leu115Ile, c.343C>A) was identified in 3 index patients (2%). We assessed the clinical phenotypes within their families and confirmed cosegregation. One carrier required heart transplantation, 2 died suddenly, and 1 died of noncardiac causes. All cases had right- and left-ventricular (LV) involvement. LV late gadolinium enhancement was present in all, and circumferential subepicardial distribution was confirmed on histology. A significant burden of ventricular arrhythmias was noted. Desmin aggregates were not observed macroscopically, but analysis of the desmin filament formation in transfected cardiomyocytes derived from induced pluripotent stem cells, and SW13 cells revealed cytoplasmic aggregation of mutant desmin. Atomic force microscopy revealed that the mutant form accumulates into short protofilaments and small fibrous aggregates. CONCLUSIONS: DES p.Leu115Ile leads to disruption of the desmin filament network and causes a malignant biventricular form of AC, characterized by LV dysfunction and a circumferential subepicardial distribution of myocardial fibrosis.

Distinct Myocardial Transcriptomic Profiles of Cardiomyopathies Stratified by the Mutant Genes.

Cardiovascular diseases are the number one cause of morbidity and mortality worldwide, but the underlying molecular mechanisms remain not well understood. Cardiomyopathies are primary diseases of the heart muscle and contribute to high rates of heart failure and sudden cardiac deaths. Here, we distinguished four different genetic cardiomyopathies based on gene expression signatures. In this study, RNA-Sequencing was used to identify gene expression signatures in myocardial tissue of cardiomyopathy patients in comparison to non-failing human hearts. Therefore, expression differences between patients with specific affected genes, namely LMNA (lamin A/C), RBM20 (RNA binding motif protein 20), TTN (titin) and PKP2 (plakophilin 2) were investigated. We identified genotype-specific differences in regulated pathways, Gene Ontology (GO) terms as well as gene groups like secreted or regulatory proteins and potential candidate drug targets revealing specific molecular pathomechanisms for the four subtypes of genetic cardiomyopathies. Some regulated pathways are common between patients with mutations in RBM20 and TTN as the splice factor RBM20 targets amongst other genes TTN, leading to a similar response on pathway level, even though many differentially expressed genes (DEGs) still differ between both sample types. The myocardium of patients with mutations in LMNA is widely associated with upregulated genes/pathways involved in immune response, whereas mutations in PKP2 lead to a downregulation of genes of the extracellular matrix. Our results contribute to further understanding of the underlying molecular pathomechanisms aiming for novel and better treatment of genetic cardiomyopathies.