14-3-3ε gene variants in a Japanese patient with left ventricular noncompaction and hypoplasia of the corpus callosum

Left ventricular noncompaction: a disorder with genotypic and phenotypic heterogeneity-a narrative review

Background and Objective

Left ventricular noncompaction (LVNC) is a cardiomyopathy characterized by excessive trabecular formation and deep recesses in the ventricular wall, with a bilaminar structure consisting of an endocardial noncompaction layer and an epicardial compacted layer. Although genetic variants have been reported in patients with LVNC, understanding of LVNC and its pathogenesis has not yet been fully elucidated. We addressed the latest findings on genes reported to be associated with LVNC morphogenesis and possible pathologies to understand the diverse spectrum between genotype and phenotype in LVNC. Also, the latest findings and issues related to the diagnosis of LVNC were summarized.

Methods

This article is written as a commentary narrative review and will provide an update on the current literature and available data on common forms of LVNC published in the past 30 years in English through to May 2022 using PubMed.

Key Content and Findings

Familial forms of LVNC are frequent, and autosomal dominant mode of inheritance has been predominantly observed. Several of the candidate causative genes are also mutated in other cardiomyopathies, suggesting a possible shared molecular and/or cellular etiology. The most common gene functions were sarcomere function whereas genes in mice LVNC models were involved in heart development. Echocardiography and cardiac magnetic resonance imaging (CMR) are useful for diagnosis although there are no unified criteria due to overdiagnosis of imaging, poor consistency between techniques, and lack of association between trabecular severity and adverse clinical outcomes.

Conclusions

This review reflects the current lack of clarity regarding the pathogenesis and significance of LVNC and showed the complexity of imaging diagnostic criteria, interpretation of the role of LVNC as a cause, and uncertainty regarding the specific genetic basis of LVNC.

Overlap phenotypes of the left ventricular noncompaction and hypertrophic cardiomyopathy with complex arrhythmias and heart failure induced by the novel truncated DSC2 mutation

Background

The left ventricular noncompaction cardiomyopathy (LVNC) is a rare subtype of cardiomyopathy associated with a high risk of heart failure (HF), thromboembolism, arrhythmia, and sudden cardiac death.

Methods

The proband with overlap phenotypes of LVNC and hypertrophic cardiomyopathy (HCM) complicates atrial fibrillation (AF), ventricular tachycardia (VT), and HF due to the diffuse myocardial lesion, which were diagnosed by electrocardiogram, echocardiogram and cardiac magnetic resonance imaging. Peripheral blood was collected from the proband and his relatives. DNA was extracted from the peripheral blood of proband for high-throughput target capture sequencing. The Sanger sequence verified the variants. The protein was extracted from the skin of the proband and healthy volunteer. The expression difference of desmocollin2 was detected by Western blot.

Results

The novel heterozygous truncated mutation (p.K47Rfs*2) of the DSC2 gene encoding an important component of desmosomes was detected by targeted capture sequencing. The western blots showed that the expressing level of functional desmocollin2 protein (~ 94kd) was lower in the proband than that in the healthy volunteer, indicating that DSC2 p.K47Rfs*2 obviously reduced the functional desmocollin2 protein expression in the proband.

Conclusion

The heterozygous DSC2 p.K47Rfs*2 remarkably and abnormally reduced the functional desmocollin2 expression, which may potentially induce the overlap phenotypes of LVNC and HCM, complicating AF, VT, and HF.

Translating emerging molecular genetic insights into clinical practice in inherited cardiomyopathies

Cardiomyopathies are primarily genetic disorders of the myocardium associated with higher risk of life-threatening cardiac arrhythmias, heart failure, and sudden cardiac death. The evolving knowledge in genomic medicine during the last decade has reshaped our understanding of cardiomyopathies as diseases of multifactorial nature and complex pathophysiology. Genetic testing in cardiomyopathies has subsequently grown from primarily a research tool into an essential clinical evaluation piece with important clinical implications for patients and their families. The purpose of this review is to provide with a contemporary insight into the implications of genetic testing in diagnosis, therapy, and prognosis of patients with inherited cardiomyopathies. Here, we summarize the contemporary knowledge on genotype-phenotype correlations in inherited cardiomyopathies and highlight the recent significant achievements in the field of translational cardiovascular genetics.

Inherited Cardiomyopathies and the Role of Mutations in Non-coding Regions of the Genome

Cardiomyopathies (CMs) are a group of cardiac pathologies caused by an intrinsic defect within the myocardium. The relative contribution of genetic mutations in the pathogenesis of certain CMs, such as hypertrophic cardiomyopathy (HCM), arrythmogenic right/left ventricular cardiomyopathy (ARVC) and left ventricular non-compacted cardiomyopathy (LVNC) has been established in comparison to dilated cardiomyopathy (DCM) and restrictive cardiomyopathy (RCM). The aim of this article is to review mutations in the non-coding parts of the genome, namely, microRNA, promoter elements, enhancer/silencer elements, 3′/5′UTRs and introns, that are involved in the pathogenesis CMs. Additionally, we will explore the role of some long non-coding RNAs in the pathogenesis of CMs.

Left Ventricular Noncompaction: A Distinct Genetic Cardiomyopathy?

Left ventricular noncompaction (LVNC) describes a ventricular wall anatomy characterized by prominent left ventricular (LV) trabeculae, a thin compacted layer, and deep intertrabecular recesses. Individual variability is extreme, and trabeculae represent a sort of individual "cardioprinting." By itself, the diagnosis of LVNC does not coincide with that of a "cardiomyopathy" because it can be observed in healthy subjects with normal LV size and function, and it can be acquired and is reversible. Rarely, LVNC is intrinsically part of a cardiomyopathy; the paradigmatic examples are infantile tafazzinopathies. When associated with LV dilation and dysfunction, hypertrophy, or congenital heart disease, the genetic cause may overlap. The prevalence of LVNC in healthy athletes, its possible reversibility, and increasing diagnosis in healthy subjects suggests cautious use of the term LVNC cardiomyopathy, which describes the morphology but not the functional profile of the cardiomyopathy.

14-3-3epsilon controls multiple developmental processes in the mouse heart

BACKGROUND

14-3-3ε plays an important role in the maturation of the compact ventricular myocardium by modulating the cardiomyocyte cell cycle via p27kip1 . However, additional cardiac defects are possible given the ubiquitous expression pattern of this protein.

RESULTS

Germ line deletion of 14-3-3ε led to malalignment of both the outflow tract (OFT) and atrioventricular (AV) cushions, with resulting tricuspid stenosis and atresia, mitral valve abnormalities, and perimembranous ventricular septal defects (VSDs). We confirmed myocardial non-compaction and detected a spongy septum with muscular VSDs and blebbing of the epicardium. These defects were associated with abnormal patterning of p27kip1 expression in the subendocardial and possibly the epicardial cell populations. In addition to abnormal pharyngeal arch artery patterning, we found deep endocardial recesses and paucity of intramyocardial coronary vasculature as a result of defective coronary plexus remodeling.

CONCLUSIONS

The malalignment of both endocardial cushions provides a new explanation for tricuspid and mitral valve defects, while myocardial non-compaction provides the basis for the abnormal coronary vasculature patterning. These abnormalities might arise from p27kip1 dysregulation and a resulting defect in epithelial-to-mesenchymal transformation. These data suggest that 14-3-3ε, in addition to left ventricular non-compaction (LVNC), might be linked to different forms of congenital heart disease (CHD). Developmental Dynamics 245:1107-1123, 2016. © 2016 Wiley Periodicals, Inc.

iPSC-derived cardiomyocytes reveal abnormal TGF-β signalling in left ventricular non-compaction cardiomyopathy

Left ventricular non-compaction (LVNC) is the third most prevalent cardiomyopathy in children and its pathogenesis has been associated with the developmental defect of the embryonic myocardium. We show that patient-specific induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) generated from LVNC patients carrying a mutation in the cardiac transcription factor TBX20 recapitulate a key aspect of the pathological phenotype at the single-cell level and this was associated with perturbed transforming growth factor beta (TGF-β) signalling. LVNC iPSC-CMs have decreased proliferative capacity due to abnormal activation of TGF-β signalling. TBX20 regulates the expression of TGF-β signalling modifiers including one known to be a genetic cause of LVNC, PRDM16, and genome editing of PRDM16 caused proliferation defects in iPSC-CMs. Inhibition of TGF-β signalling and genome correction of the TBX20 mutation were sufficient to reverse the disease phenotype. Our study demonstrates that iPSC-CMs are a useful tool for the exploration of pathological mechanisms underlying poorly understood cardiomyopathies including LVNC.

Micro-Computed Tomography for the Quantitative 3-Dimensional Assessment of the Compact Myocardium in the Mouse Embryo

BACKGROUND

Ventricular non-compaction is characterized by a thin layer of compact ventricular myocardium and it is an important abnormality in the mouse heart. It is reminiscent of left ventricular non-compaction, a fairly common human congenital cardiomyopathy. Non-compaction in transgenic mice has been classically evaluated by measuring the thickness of the compact myocardium through histological techniques involving image analysis of 2-dimensional (D) sections. Given the 3D nature of the heart, the aim of this study was to determine whether a technique for the non-destructive, 3D assessment of the mouse embryonic compact myocardium could be developed.

METHODS AND RESULTS

Micro-computed tomography (micro-CT), in combination with iodine staining, enabled the differentiation of the trabecular from the compact myocardium in wild-type mice. The 3D and digital nature of the micro-CT data allowed computation anatomical techniques to be readily applied, which were demonstrated via construction of group atlases and atlas-based descriptive statistics. Finally, micro-CT was used to identify the presence of non-compaction in mice with a deletion of the cell cycle inhibitor protein, p27(Kip1).

CONCLUSIONS

Iodine staining-enhanced micro-CT with computational anatomical analysis represents a valid addition to classical histology for the delineation of compact myocardial wall thickness in the mouse embryo. Given the quantitative 3D resolution of micro-CT, these approaches might provide helpful information for the analysis of non-compaction. (Circ J 2016; 80: 1795-1803).

14-3-3γ protein attenuates lipopolysaccharide-induced cardiomyocytes injury through the Bcl-2 family/mitochondria pathway

Previous studies have indicated that 14-3-3γ is upregulated by stress in LPS-induced cardiovascular injury. In this study, we investigated the interaction of 14-3-3γ and Bcl-2 family members in the control of the mitochondrial permeability transition (MPT) to test the hypothesis that abundant levels of 14-3-3γ can protect against LPS-induced injury via a Bcl-2 family/mitochondria pathway. The cardiomyocytes were treated with LPS (1mg l(-1)) for 6h; the interaction between 14-3-3γ and phospho-Bad(S112) was detected by co-immunoprecipitation (co-IP); the levels of Bcl-2 family members in the cytosolic and mitochondrial fractions were examined by Western blot; the apoptosis and mitochondrial membrane potential (ΔΨm) were detected by flow cytometry; and the mitochondrial permeability transition pore (mPTP) opening was tested by mitochondrial swelling. Our results revealed that LPS treatment results in cardiomyocyte injury, and these effects were significantly attenuated by pFLAG-14-3-3γ. Moreover, LPS treatment induced Bax translocation to the mitochondria, ΔΨm loss, mitochondrial swelling, and cytochrome c release, and pFLAG-14-3-3γ reversed these effects induced by LPS. Moreover, overexpressed 14-3-3γ protein could assist Bad(S112) phosphorylation and interact with it to form a complex, which might result in the disassociation of Bcl-2 from the Bad/Bcl-2 complex and its translocation from the cytosol to the mitochondria. Our data firstly confirmed that a high level of 14-3-3γ protects against LPS-induced cardiomyocyte injury likely through a pathway associated with the regulation of the subcellular localizations of Bcl-2 and Bad that results in the prevention of mPTP opening, the maintenance of ΔΨm, and ultimately the inhibition of apoptosis.

Molecular mechanism of ventricular trabeculation/compaction and the pathogenesis of the left ventricular noncompaction cardiomyopathy (LVNC)

Ventricular trabeculation and compaction are two of the many essential steps for generating a functionally competent ventricular wall. A significant reduction in trabeculation is usually associated with ventricular compact zone deficiencies (hypoplastic wall), which commonly leads to embryonic heart failure and early embryonic lethality. In contrast, hypertrabeculation and lack of ventricular wall compaction (noncompaction) are closely related defects in cardiac embryogenesis associated with left ventricular noncompaction (LVNC), a genetically heterogenous disorder. Here we review recent findings through summarizing several genetically engineered mouse models that have defects in cardiac trabeculation and compaction.