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D117N in Cypher/ZASP may not be a causative mutation for dilated cardiomyopathy and ventricular arrhythmias.

ABSTRACT: Dilated cardiomyopathy (DCM) and malignant ventricular arrhythmias are important causes of congestive heart failure, heart transplantation, and sudden cardiac death in young patients. Cypher/ZASP is a cytoskeletal protein localized in the sarcomeric Z-line that has a pivotal role in maintaining adult cardiac structure and function. The putative mutation p.(D117N) in Cypher/ZASP has been suggested to cause systolic dysfunction, dilated left ventricle with hypertrabeculated myocardium, and intraventricular conduction disturbance, based on two reported sporadic cases. In two unrelated Bedouin families, one with pediatric DCM and the other with DCM and ventricular arrhythmias at young adulthood searching for the causative mutation by exome sequencing we identified the p.(D117N) variant in Cypher/ZASP. However, p.(D117N) did not segregate as the causative mutation in these families, i.e. it was not present in some patients and was found in several individuals who had no clinical manifestations. Furthermore, the carrier frequency in the Bedouin population of origin is estimated to be 5.2%, which is much higher than the incidence of idiopathic DCM in this population. Thus, our data support the notion that the p.(D117N) variant in Cypher/ZASP is not a causative mutation in the families tested by us. The results also indicates that at least in some cases, the p.(D117N) in Cypher/ZASP is not a causative mutation and the role of D117N in Cypher/ZASP in cardiac pathologies should be further clarified and re-evaluated.

SUBMITTER: Levitas A

PROVIDER: S-EPMC4930098 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:AimsPatients with non-ischaemic dilated cardiomyopathy (DCM) are at increased risk of sudden cardiac death. Identification of patients that may benefit from implantable cardioverter-defibrillator implantation remains challenging. In this study, we aimed to determine predictors of sustained ventricular arrhythmias in patients with DCM.Methods and resultsWe searched MEDLINE/Embase for studies describing predictors of sustained ventricular arrhythmias in patients with DCM. Quality and bias were assessed using the Quality in Prognostic Studies tool, articles with high risk of bias in ≥2 areas were excluded. Unadjusted hazard ratios (HRs) of uniformly defined predictors were pooled, while all other predictors were evaluated in a systematic review. We included 55 studies (11 451 patients and 3.7 ± 2.3 years follow-up). Crude annual event rate was 4.5%. Younger age [HR 0.82; 95% CI (0.74-1.00)], hypertension [HR 1.95; 95% CI (1.26-3.00)], prior sustained ventricular arrhythmia [HR 4.15; 95% CI (1.32-13.02)], left ventricular ejection fraction on ultrasound [HR 1.45; 95% CI (1.19-1.78)], left ventricular dilatation (HR 1.10), and presence of late gadolinium enhancement [HR 5.55; 95% CI (4.02-7.67)] were associated with arrhythmic outcome in pooled analyses. Prior non-sustained ventricular arrhythmia and several genotypes [mutations in Phospholamban (PLN), Lamin A/C (LMNA), and Filamin-C (FLNC)] were associated with arrhythmic outcome in non-pooled analyses. Quality of evidence was moderate, and heterogeneity among studies was moderate to high.ConclusionsIn patients with DCM, the annual event rate of sustained ventricular arrhythmias is approximately 4.5%. This risk is considerably higher in younger patients with hypertension, prior (non-)sustained ventricular arrhythmia, decreased left ventricular ejection fraction, left ventricular dilatation, late gadolinium enhancement, and genetic mutations (PLN, LMNA, and FLNC). These results may help determine appropriate candidates for implantable cardioverter-defibrillator implantation.

Project description:Rationale: Cardiomyocytes (CMs) undergo dramatic structural and functional changes in postnatal maturation; however, the regulatory mechanisms remain greatly unclear. Cypher/Z-band alternatively spliced PDZ-motif protein (ZASP) is an essential sarcomere component maintaining Z-disc stability. Deletion of mouse Cypher and mutation in human ZASP result in dilated cardiomyopathy (DCM). Whether Cypher/ZASP participates in CM maturation and thereby affects cardiac function has not been answered. Methods: Immunofluorescence, transmission electron microscopy, real-time quantitative PCR, and Western blot were utilized to identify the role of Cypher in CM maturation. Subsequently, RNA sequencing and bioinformatics analysis predicted serum response factor (SRF) as the key regulator. Rescue experiments were conducted using adenovirus or adeno-associated viruses encoding SRF, both in vitro and in vivo. The molecular mechanisms were elucidated through G-actin/F-actin fractionation, nuclear-cytoplasmic extraction, actin disassembly assays, and co-sedimentation assays. Results: Cypher deletion led to impaired sarcomere isoform switch and morphological abnormalities in mitochondria, transverse-tubules, and intercalated discs. RNA-sequencing analysis revealed significant dysregulation of crucial genes related to sarcomere assembly, mitochondrial metabolism, and electrophysiology in the absence of Cypher. Furthermore, SRF was predicted as key transcription factor mediating the transcriptional differences. Subsequent rescue experiments showed that SRF re-expression during the critical postnatal period effectively rectified CM maturation defects and notably improved cardiac function in Cypher-depleted mice. Mechanistically, Cypher deficiency resulted in the destabilization of F-actin and a notable increase in G-actin levels, thereby impeding the nuclear localisation of myocardin-related transcription factor A (MRTFA) and subsequently initiating SRF transcription. Conclusion: Cypher/ZASP plays a crucial role in CM maturation through actin-mediated MRTFA-SRF signalling. The linkage between CM maturation abnormalities and the late-onset of DCM is suggested, providing further insights into the pathogenesis of DCM and potential treatment strategies.

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D117N in Cypher/ZASP may not be a causative mutation for dilated cardiomyopathy and ventricular arrhythmias.

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