Aims: Arrhythmogenic cardiomyopathy (AC) shows large heterogeneity in its clinical, genetic, and pathological presentation. This study aims to provide a comprehensive atlas of end-stage AC and illustrate the relationships among clinical characteristics, genotype, and pathological profiles of patients with this disease. Methods and results: We collected 60 explanted AC hearts and performed standard pathology examinations. The clinical characteristics of patients, their genotype and cardiac magnetic resonance imaging findings were assessed along with pathological characteristics. Masson staining of six representative sections of each heart were performed. Digital pathology combined with image segmentation was developed to calculate distribution of myocardium, fibrosis, and adipose tissue. An unsupervised clustering based on fibrofatty distribution containing four subtypes was constructed. Patients in Cluster 1 mainly carried desmosomal mutations (except for desmoplakin) and were subjected to transplantation at early age; this group was consistent with classical ‘desmosomal cardiomyopathy’. Cluster 2 mostly had non-desmosomal mutations and showed regional fibrofatty replacement in right ventricle. Patients in Cluster 3 showed parallel progression, and included patients with desmoplakin mutations. Cluster 4 is typical left-dominant AC, although the genetic background of these patients is not yet clear. Multivariate regression analysis revealed precordial QRS voltage as an independent indicator of the residual myocardium of right ventricle, which was validated in predicting death and transplant events in the validation cohort (n = 92). Conclusion: This study provides a novel classification of AC with distinct genetic backgrounds indicating different potential pathogenesis. Cluster 1 is distinct in genotype and clinicopathology and can be defined as ‘desmosomal cardiomyopathy’. Precordial QRS amplitude is an independent indicator reflecting the right ventricular remodelling, which may be able to predict transplant/death events for AC patients.

Background: Real-time quantitative polymerase chain reaction (RT-qPCR) is a widely-used standard assay for assessing gene expression. RT-qPCR data requires reference genes for normalization to make the results comparable. Therefore, the selected reference gene should be highly stable in its expression throughout the experimental datasets. So far, reports about the optimal set of reference genes in murine left ventricle (LV) across embryonic and postnatal stages are few. The objective of our research was to identify the appropriate reference genes in murine LV among different developmental stages. Methods: We investigated the gene expression profiles of 21 widely used housekeeping genes in murine LV from 7 different developmental stages (almost throughout the whole period of the mouse lifespan). The stabilities of the potential reference genes were evaluated by five methods: GeNorm, NormFinder, BestKeeper, Delta-Ct and RefFinder. Results: We proposed a set of reliable reference genes for normalization of RT-qPCR experimental data in different conditions. Furthermore, our results showed that 6 genes (18S, Hmbs, Ubc, Psmb4, Tfrc and Actb) are not recommended to be used as reference genes in murine LV development studies. The data also suggested that the Rplp0 gene might serve as an optimal reference gene in gene expression analysis. Conclusions: Our study investigated the expression stability of the commonly used reference genes in process of LV development and maturation. We proposed a set of optimal reference genes that are suitable for accurate normalization of RT-qPCR data in specific conditions. Our findings may be helpful in future studies for investigating the gene expression patterns and mechanism of mammalian heart development.

Aims: Arrhythmogenic cardiomyopathy (ACM) is a genetically-determined disease characterized by malignant arrhythmias and sudden cardiac death, particularly in young individuals. Mutations in desmosomal genes are a major cause of ACM, but the role of desmocollin-2 (DSC2) remains understudied. Methods and results: We conducted a multi-cohort study with 52 ACM patients, 29 with dilated cardiomyopathy (DCM), 17 with hypertrophic cardiomyopathy (HCM), and 45 controls. Immunofluorescence, immunohistochemical staining, and western blot were used to assess DSC2 expression. DSC2 expression was significantly reduced in ACM myocardium compared to controls and other cardiomyopathies (P < 0.0001), consistent across ACM subtypes and validated in an independent cohort. DSC2 down-regulation correlated with clinical characteristics such as age at onset of arrhythmia and heart transplantation. DSC2 reduction in the right ventricle effectively discriminated ACM patients from controls (ROC AUC = 0.8017, P < 0.0001) and distinguished ACM from other cardiac diseases. Immunohistochemical staining in the Swiss cohort confirmed that 11 out of 12 (91.7%) ACM cases exhibited significantly reduced DSC2 signal intensity compared to normal donors. RNA-Seq analysis revealed significant down-regulation of DSC2 genes in ACM tissues. Conclusion: DSC2 remodelling is a hallmark of ACM, harbouring significant diagnostic implications. DSC2 reduction is a robust biomarker for ACM, showing high sensitivity and specificity across different subtypes. Future research should elucidate the mechanisms underlying DSC2 down-regulation.

Aims: Real-time quantitative polymerase chain reaction (RT-qPCR) is the standard assay used for revealing the gene expression characteristics. However, the RT-qPCR studies all need reference genes for normalization to make the results comparable, which should hold a high expression stability during all experimental datasets. So far, there was no optimal set of reference genes identified in mice left ventricles (LV) across embryonic and postnatal stages. The objective of our research was to identify the appropriate reference genes in mice LV from different developmental stages.Methods and Results: we investigated the gene expressions of common 21 candidate housekeeping genes in mice LV from 7 different developmental stages, almost throughout the whole period of the mouse lifespan. The expression of some candidate reference genes, such as 18S and Actb, apparently fluctuated. The stability of potential reference genes was evaluated by a number of methods, such as GeNorm, NormFinder, BestKeeper, Delta-Ct and RefFinder method. we identified a set of optimal reference genes that can be reliably used for normalization of RT-qPCR experiments in different developmental stages of mice LV. Our results showed that following genes should not be used as reference genes in mice LV development studies: 18S, Hmbs, Ubc, Psmb4, Tfrc and Actb. And the Rplp0 appeared to represent a good choice. Conclusions: Our study provides the expression stability of the commonly used reference genes in process of LV development and maturation. We also identified a set of optimal reference genes under different conditions. Our findings may be helpful in future studies to investigate the gene expression patterns and mechanism of mammalian heart development.