Variants of the promoter of MYH6 gene in congenital isolated and sporadic patent ductus arteriosus: case-control study and cellular functional analyses

Patent ductus arteriosus (PDA) is a common form of congenital heart disease. The MYH6 gene has important effects on cardiovascular growth and development, but the effect of variants in the MYH6 gene promoter on ductus arteriosus is unknown. DNA was extracted from blood samples of 721 subjects (428 patients with isolated and sporadic PDA and 293 healthy controls) and analyzed by sequencing for MYH6 gene promoter region variants. Cellular function experiments with three cell lines (HEK-293, HL-1, and H9C2 cells) and bioinformatics analyses were performed to verify their effects on gene expression. In the MYH6 gene promoter, 11 variants were identified. Four variants were found only in patients with PDA and 2 of them (g.3434G>C and g.4524C>T) were novel. Electrophoretic mobility shift assay showed that the transcription factors bound by the promoter variants were significantly altered in comparison to the wild-type in all three cell lines. Dual luciferase reporter showed that all the 4 variants reduced the transcriptional activity of the MYH6 gene promoter (P < 0.05). Prediction of transcription factors bound by the variants indicated that these variants alter the transcription factor binding sites. These pathological alterations most likely affect the contraction of the smooth muscle of ductus arteriosus, leading to PDA. This study is the first to focus on variants at the promoter region of the MYH6 gene in PDA patients with cellular function tests. Therefore, this study provides new insights to understand the genetic basis and facilitates further studies on the mechanism of PDA formation.

Using whole genome sequence findings to assess gene-disease causality in cardiomyopathy and arrhythmia patients

Aim: The genetic etiologies of cardiomyopathies and arrhythmias have not been fully elucidated. Materials & methods: Research findings from genome analyses in a cardiomyopathy and arrhythmia cohort were gathered. Gene-disease relationships from two databases were compared with patient phenotypes. A literature review was conducted for genes with limited evidence. Results: Of 43 genes with candidate findings from 18 cases, 23.3% of genes had never been curated, 15.0% were curated for cardiomyopathies, 16.7% for arrhythmias and 31.3% for other conditions. 25.5% of candidate findings were curated for the patient's specific phenotype with 11.8% having definitive evidence. MYH6 and TPCN1 were flagged for recuration. Conclusion: Findings from genome sequencing in disease cohorts may be useful to guide gene-curation efforts.

Changes of ubiquitylated proteins in atrial fibrillation associated with heart valve disease: proteomics in human left atrial appendage tissue

Background

Correlations between posttranslational modifications and atrial fibrillation (AF) have been demonstrated in recent studies. However, it is still unclear whether and how ubiquitylated proteins relate to AF in the left atrial appendage of patients with AF and valvular heart disease.

Methods

Through LC-MS/MS analyses, we performed a study on tissues from eighteen subjects (9 with sinus rhythm and 9 with AF) who underwent cardiac valvular surgery. Specifically, we explored the ubiquitination profiles of left atrial appendage samples.

Results

In summary, after the quantification ratios for the upregulated and downregulated ubiquitination cutoff values were set at >1.5 and <1:1.5, respectively, a total of 271 sites in 162 proteins exhibiting upregulated ubiquitination and 467 sites in 156 proteins exhibiting downregulated ubiquitination were identified. The ubiquitylated proteins in the AF samples were enriched in proteins associated with ribosomes, hypertrophic cardiomyopathy (HCM), glycolysis, and endocytosis.

Conclusions

Our findings can be used to clarify differences in the ubiquitination levels of ribosome-related and HCM-related proteins, especially titin (TTN) and myosin heavy chain 6 (MYH6), in patients with AF, and therefore, regulating ubiquitination may be a feasible strategy for AF.

Prenatal diagnosis of recurrent hypoplastic left heart syndrome associated with MYH6 variants: a case report

BACKGROUND

Hypoplastic left heart syndrome (HLHS) is a rare but genetically complex and clinically and anatomically severe form of congenital heart disease (CHD).

CASE PRESENTATION

Here, we report on the use of rapid prenatal whole-exome sequencing for the prenatal diagnosis of a severe case of neonatal recurrent HLHS caused by heterozygous compound variants in the MYH6 gene inherited from the (healthy) parents. MYH6 is known to be highly polymorphic; a large number of rare and common variants have variable effects on protein levels. We postulated that two hypomorphic variants led to severe CHD when associated in trans; this was consistent with the autosomal recessive pattern of inheritance. In the literature, dominant transmission of MYH6-related CHD is more frequent and is probably linked to synergistic heterozygosity or the specific combination of a single, pathogenic variant with common MYH6 variants.

CONCLUSIONS

The present report illustrates the major contribution of whole-exome sequencing (WES) in the characterization of an unusually recurrent fetal disorder and considered the role of WES in the prenatal diagnosis of disorders that do not usually have a genetic etiology.

Identification and functional analysis of variants of MYH6 gene promoter in isolated ventricular septal defects

Background

Ventricular septal defect is the most common form of congenital heart diseases. MYH6 gene has a critical effect on the growth and development of the heart but the variants in the promoter of MYH6 is unknown.

Patients and methods

In 604 of the subjects (311 isolated and sporadic ventricular septal defect patients and 293 healthy controls), DNA was extracted from blood samples and MYH6 gene promoter region variants were analyzed by sequencing. Further functional verification was performed by cellular experiments using dual luciferase reporter gene analysis, electrophoretic mobility shift assays, and bioinformatics analysis.

Results

Nine variants were identified in the MYH6 gene promoter and two of those variants [g.4085G>C(rs1222539675) and g.4716G>A(rs377648095)] were only found in the ventricular septal defect patients. Cellular function experiments showed that these two variants reduced the transcriptional activity of the MYH6 gene promoter (p < 0.001). Further analysis with online JASPAR database suggests that these variants may alter a set of putative transcription factor binding sites that possibly lead to changes in myosin subunit expression and ventricular septal defect formation.

Conclusions

Our study for the first time identifies variants in the promoter region of the MYH6 gene in Chinese patients with isolated and sporadic ventricular septal defect. These variants significantly reduced MYH6 gene expression and affected transcription factor binding sites and therefore are pathogenic. The present study provides new insights in the role of the MYH6 gene promoter region to better understand the genetic basis of VSD formation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01365-y.

Long non-coding RNA lincRNA-erythroid prosurvival attenuates inflammation by enhancing myosin heavy chain 6 stability through recruitment of heterogeneous nuclear ribonucleoprotein L in myocardial infarction

Myocardial infarction (MI), a prevalent cardiac disorder with high mortality, leads to severe heart injury associated with inflammation and cardiomyocyte apoptosis. Long non-coding RNAs have been widely found to participate in the progression of MI. Here, we aimed to explore the impact of lincRNA-erythroid prosurvival (EPS) on MI-induced inflammation and cardiomyocyte apoptosis. Significantly, lincRNA-EPS was lowly expressed in MI mice and in oxygen and glucose deprivation (OGD)-treated HL-1 cells. Echocardiography analysis revealed that lincRNA-EPS overexpression increased left ventricular ejection fraction and left ventricular fraction shortening, and decreased left ventricular internal diameter at end systole and left ventricular internal diameter at end diastole in a mouse model. In our study, the expression levels of interleukin-6, tumor necrosis factor-alpha, interleukin-1β, and interleukin-18 were upregulated in the MI mice and OGD-treated HL-1 cells, while lincRNA-EPS overexpression reversed these phenotypes. Meanwhile, lincRNA-EPS reduced MI-induced cardiomyocyte apoptosis in vivo and in vitro. Mechanically, lincRNA-EPS interacted with myosin heavy chain 6 (MYH6) and heterogeneous nuclear ribonucleoprotein L (HNRNPL), and the depletion of lincRNA-EPS and HNRNPL inhibited MYH6 mRNA stability in HL-1 cells. HNRNPL knockdown blocked lincRNA-EPS overexpression-induced MYH6 expression in the system. The depletion of MYH6 and HNRNPL could rescue lincRNA-EPS overexpression-reduced inflammation and apoptosis in HL-1 cells. Thus, we conclude that lincRNA-EPS attenuates inflammation and apoptosis in MI-induced myocardial injury by maintaining MYH6 stability through the recruitment of HNRNPL.

Whole Genome Sequencing in Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome (HLHS) is a genetically complex disorder. Whole genome sequencing enables comprehensive scrutiny of single nucleotide variants and small insertions/deletions, within both coding and regulatory regions of the genome, revolutionizing susceptibility-gene discovery research. Because millions of rare variants comprise an individual genome, identification of alleles linked to HLHS necessitates filtering algorithms based on various parameters, such as inheritance, enrichment, omics data, known genotype–phenotype associations, and predictive or experimental modeling. In this brief review, we highlight family and cohort-based strategies used to analyze whole genome sequencing datasets and identify HLHS candidate genes. Key findings include compound and digenic heterozygosity among several prioritized genes and genetic associations between HLHS and bicuspid aortic valve or cardiomyopathy. Together with findings of independent genomic investigations, MYH6 has emerged as a compelling disease gene for HLHS and other left-sided congenital heart diseases.

Novel insertion mutation (Arg1822_Glu1823dup) in MYH6 coiled-coil domain causing familial atrial septal defect

OBJECTIVE

Atrial septal defect, secundum (ASD Ⅱ, OMIM: 603642) is the second common congenital heart defect (CHD) in China. However, the genetic etiology of familial ASD II remains elusive.

METHODS AND RESULTS

Using whole-exome sequencing (WES) and Sanger sequencing, we identified a novel myosin heavy chain 6 (MYH6) gene insertion variation, NM_002471.3: c.5465_5470dup (Arg1822_Glu1823dup), in a large Chinese Han family with ASD II. The variant Arg1822_Glu1823dup co-segregated with the disease in this family with autosomal dominant inheritance. The insertion variant located in the coiled-coil domain of the MYH6 protein, which is highly conserved across homologous myosin proteins and species. In transfected myoblast C2C12 cell lines, the MYH6 Arg1822_Glu1823dup variant significantly impaired myofibril formation and increased apoptosis but did not significantly reduce cell viability. Furthermore, molecular simulations revealed that the Arg1822_Glu1823dup variant impaired the myosin α-helix, increasing the stability of the coiled-coil myosin dimer, suggesting that this variant has an effect on the coiled-coil domain self-aggregation. These findings indicate that Arg1822_Glu1823dup variant plays a crucial role in the pathogenesis of ASD II.

CONCLUSION

Our findings expand the spectrum of MYH6 variations associated with familial ASD II and may provide a molecular basis in genetic counseling and prenatal diagnosis for this Chinses family.

The SARS-CoV-2 SSHHPS Recognized by the Papain-like Protease

Viral proteases are highly specific and recognize conserved cleavage site sequences of ∼6-8 amino acids. Short stretches of homologous host-pathogen sequences (SSHHPS) can be found spanning the viral protease cleavage sites. We hypothesized that these sequences corresponded to specific host protein targets since >40 host proteins have been shown to be cleaved by Group IV viral proteases and one Group VI viral protease. Using PHI-BLAST and the viral protease cleavage site sequences, we searched the human proteome for host targets and analyzed the hit results. Although the polyprotein and host proteins related to the suppression of the innate immune responses may be the primary targets of these viral proteases, we identified other cleavable host proteins. These proteins appear to be related to the virus-induced phenotype associated with Group IV viruses, suggesting that information about viral pathogenesis may be extractable directly from the viral genome sequence. Here we identify sequences cleaved by the SARS-CoV-2 papain-like protease (PLpro) in vitro within human MYH7 and MYH6 (two cardiac myosins linked to several cardiomyopathies), FOXP3 (an X-linked Treg cell transcription factor), ErbB4 (HER4), and vitamin-K-dependent plasma protein S (PROS1), an anticoagulation protein that prevents blood clots. Zinc inhibited the cleavage of these host sequences in vitro. Other patterns emerged from multispecies sequence alignments of the cleavage sites, which may have implications for the selection of animal models and zoonosis. SSHHPS/nsP is an example of a sequence-specific post-translational silencing mechanism.

Contractility of Induced Pluripotent Stem Cell-Cardiomyocytes With an MYH6 Head Domain Variant Associated With Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome (HLHS) is a clinically and anatomically severe form of congenital heart disease; however, its etiology remains largely unknown. We previously demonstrated that genetic variants in the MYH6 gene are significantly associated with HLHS. Additionally, induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) from an HLHS-affected family trio (affected parent, unaffected parent, affected proband) carrying an MYH6-R443P head domain variant demonstrated dysmorphic sarcomere structure and increased compensatory MYH7 expression. Analysis of iPSC-CMs derived from the HLHS trio revealed that only beta myosin heavy chain expression was observed in CMs carrying the MYH6-R443P variant after differentiation day 15 (D15). Functional assessments performed between D20-D23 revealed that MYH6-R443P variant CMs contracted more slowly (40 ± 2 vs. 47 ± 2 contractions/min, P < 0.05), shortened less (5.6 ± 0.5 vs. 8.1 ± 0.7% of cell length, P < 0.05), and exhibited slower shortening rates (19.9 ± 1.7 vs. 28.1 ± 2.5 μm/s, P < 0.05) and relaxation rates (11.0 ± 0.9 vs. 19.7 ± 2.0 μm/s, P < 0.05). Treatment with isoproterenol had no effect on iPSC-CM mechanics. Using CRISPR/Cas9 gene editing technology, introduction of the R443P variant into the unaffected parent's iPSCs recapitulated the phenotype of the proband's iPSC-CMs, and conversely, correction of the R443P variant in the proband's iPSCs rescued the cardiomyogenic differentiation, sarcomere organization, slower contraction (P < 0.05) and decreased velocity phenotypes (P < 0.0001). This is the first report to identify that cardiac tissues from HLHS patients with MYH6 variants can exhibit sarcomere disorganization in atrial but not ventricular tissues. This new discovery was not unexpected, since MYH6 is expressed predominantly in the postnatal atria in humans. These findings demonstrate the feasibility of employing patient-derived iPSC-CMs, in combination with patient cardiac tissues, to gain mechanistic insight into how genetic variants can lead to HLHS. Results from this study suggest that decreased contractility of CMs due to sarcomere disorganization in the atria may effect hemodynamic changes preventing development of a normal left ventricle.

Advanced Single-Cell Mapping Reveals that in hESC Cardiomyocytes Contraction Kinetics and Action Potential Are Independent of Myosin Isoform

Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) represent an attractive model to investigate CM function and disease mechanisms. One characteristic marker of ventricular specificity of human CMs is expression of the ventricular, slow β-myosin heavy chain (MyHC), as opposed to the atrial, fast α-MyHC. The main aim of this study was to investigate at the single-cell level whether contraction kinetics and electrical activity of hESC-CMs are influenced by the relative expression of α-MyHC versus β-MyHC. For effective assignment of functional parameters to the expression of both MyHC isoforms at protein and mRNA levels in the very same hESC-CMs, we developed a single-cell mapping technique. Surprisingly, α- versus β-MyHC was not related to specific contractile or electrophysiological properties of the same cells. The multiparametric cell-by-cell analysis suggests that in hESC-CMs the expression of genes associated with electrical activity, contraction, calcium handling, and MyHCs is independently regulated.

A human embryonic stem cell reporter line for monitoring chemical-induced cardiotoxicity

AIMS

Human embryonic stem cells (hESCs) can be used to generate scalable numbers of cardiomyocytes (CMs) for studying cardiac biology, disease modelling, drug screens, and potentially for regenerative therapies. A fluorescence-based reporter line will significantly enhance our capacities to visualize the derivation, survival, and function of hESC-derived CMs. Our goal was to develop a reporter cell line for real-time monitoring of live hESC-derived CMs.

METHODS AND RESULTS

We used CRISPR/Cas9 to knock a mCherry reporter gene into the MYH6 locus of hESC lines, H1 and H9, enabling real-time monitoring of the generation of CMs. MYH6:mCherry+ cells express atrial or ventricular markers and display a range of cardiomyocyte action potential morphologies. At 20 days of differentiation, MYH6:mCherry+ cells show features characteristic of human CMs and can be used successfully to monitor drug-induced cardiotoxicity and oleic acid-induced cardiac arrhythmia.

CONCLUSION

We created two MYH6:mCherry hESC reporter lines and documented the application of these lines for disease modelling relevant to cardiomyocyte biology.

Whole-exome sequencing identifies R1279X of MYH6 gene to be associated with congenital heart disease

BACKGROUND

Myosin VI, encoded by MYH6, is expressed dominantly in human cardiac atria and plays consequential roles in cardiac muscle contraction and comprising the cardiac muscle thick filament. It has been reported that the mutations in the MYH6 gene associated with sinus venosus atrial septal defect (ASD type III), hypertrophic (HCM) and dilated (DCM) cardiomyopathies.

METHODS

Two patients in an Iranian family have been identified who affected to Congenital Heart Disease (CHD). The male patient, besides CHD, shows that the thyroglossal sinus, refractive errors of the eye and mitral stenosis. The first symptoms emerged at the birth and diagnosis based on clinical features was made at about 5 years. The family had a history of ASD. For recognizing mutated gene (s), whole exome sequencing (WES) was performed for the male patient and variants were analyzed by autosomal dominant inheritance mode.

RESULTS

Eventually, by several filtering processes, a mutation in MYH6 gene (NM_002471.3), c.3835C > T; R1279X, was identified as the most likely disease-susceptibility variant and then confirmed by Sanger sequencing in the family. The mutation frequency was checked out in the local databases. This mutation results in the elimination of the 660 amino acids in the C-terminal of Myosin VI protein, including the vital parts of the coiled-coil structure of the tail domain.

CONCLUSIONS

Our study represents the first case of Sinus venosus defect caused directly by MYH6 stop codon mutation. Our data indicate that by increase haploinsufficiency of myosin VI, c.3835C > T mutation with reduced penetrance could be associated with CHD.

Isolated Ventricular Noncompaction Cardiomyopathy Presenting as Fetal Hydrops at 24 Weeks Gestation

Ventricular noncompaction cardiomyopathy is a rare form of congenital cardiomyopathy with increasing evidence of genetic etiology, especially when presenting in childhood. Fetal presentation is rare. We describe a case of fetal hydrops, presenting at 24 weeks gestation and leading to intrapartum death at 26 weeks gestation. Autopsy examination revealed characteristic features of left ventricular noncompaction. A genetic analysis identified a constellation of variants of unknown significance in MYH6, TNNC1, and MYBPC3, genes known to be important in sarcomeric function. Additionally, the variant in MYBPC3 was homozygous. While this case did not demonstrate a conventional single-gene mutation as the cause of the ventricular noncompaction, a broader genomic investigation revealed several variants in sarcomeric genes which may act synergistically to impact cardiac function.

Sucrose Nonfermenting-Related Kinase Enzyme-Mediated Rho-Associated Kinase Signaling is Responsible for Cardiac Function

BACKGROUND

Cardiac metabolism is critical for the functioning of the heart, and disturbance in this homeostasis is likely to influence cardiac disorders or cardiomyopathy. Our laboratory has previously shown that SNRK (sucrose nonfermenting related kinase) enzyme, which belongs to the AMPK (adenosine monophosphate-activated kinase) family, was essential for cardiac metabolism in mammals. Snrk global homozygous knockout (KO) mice die at postnatal day 0, and conditional deletion of Snrk in cardiomyocytes (Snrk cmcKO) leads to cardiac failure and death by 8 to 10 months.

METHODS AND RESULTS

We performed additional cardiac functional studies using echocardiography and identified further cardiac functional deficits in Snrk cmcKO mice. Nuclear magnetic resonance-based metabolomics analysis identified key metabolic pathway deficits in SNRK knockdown cardiomyocytes in vitro. Specifically, metabolites involved in lipid metabolism and oxidative phosphorylation are altered, and perturbations in these pathways can result in cardiac function deficits and heart failure. A phosphopeptide-based proteomic screen identified ROCK (Rho-associated kinase) as a putative substrate for SNRK, and mass spec-based fragment analysis confirmed key amino acid residues on ROCK that are phosphorylated by SNRK. Western blot analysis on heart lysates from Snrk cmcKO adult mice and SNRK knockdown cardiomyocytes showed increased ROCK activity. In addition, in vivo inhibition of ROCK partially rescued the in vivo Snrk cmcKO cardiac function deficits.

CONCLUSIONS

Collectively, our data suggest that SNRK in cardiomyocytes is responsible for maintaining cardiac metabolic homeostasis, which is mediated in part by ROCK, and alteration of this homeostasis influences cardiac function in the adult heart.

Exome analysis of a family with Wolff-Parkinson-White syndrome identifies a novel disease locus

Wolff-Parkinson-White (WPW) syndrome is a common cause of supraventricular tachycardia that carries a risk of sudden cardiac death. To date, mutations in only one gene, PRKAG2, which encodes the 5'-AMP-activated protein kinase subunit γ-2, have been identified as causative for WPW. DNA samples from five members of a family with WPW were analyzed by exome sequencing. We applied recently designed prioritization strategies (VAAST/pedigree VAAST) coupled with an ontology-based algorithm (Phevor) that reduced the number of potentially damaging variants to 10: a variant in KCNE2 previously associated with Long QT syndrome was also identified. Of these 11 variants, only MYH6 p.E1885K segregated with the WPW phenotype in all affected individuals and was absent in 10 unaffected family members. This variant was predicted to be damaging by in silico methods and is not present in the 1,000 genome and NHLBI exome sequencing project databases. Screening of a replication cohort of 47 unrelated WPW patients did not identify other likely causative variants in PRKAG2 or MYH6. MYH6 variants have been identified in patients with atrial septal defects, cardiomyopathies, and sick sinus syndrome. Our data highlight the pleiotropic nature of phenotypes associated with defects in this gene.

Novel mutation in the α-myosin heavy chain gene is associated with sick sinus syndrome

BACKGROUND

Recent genome-wide association studies have demonstrated an association between MYH6, the gene encoding α-myosin heavy chain (α-MHC), and sinus node function in the general population. Moreover, a rare MYH6 variant, R721W, predisposing susceptibility to sick sinus syndrome has been identified. However, the existence of disease-causing MYH6 mutations for familial sick sinus syndrome and their underlying mechanisms remain unknown.

METHODS AND RESULTS

We screened 9 genotype-negative probands with sick sinus syndrome families for mutations in MYH6 and identified an in-frame 3-bp deletion predicted to delete one residue (delE933) at the highly conserved coiled-coil structure within the binding motif to myosin-binding protein C in one patient. Co-immunoprecipitation analysis revealed enhanced binding of delE933 α-MHC to myosin-binding protein C. Irregular fluorescent speckles retained in the cytoplasm with substantially disrupted sarcomere striation were observed in neonatal rat cardiomyocytes transfected with α-MHC mutants carrying delE933 or R721W. In addition to the sarcomere impairments, delE933 α-MHC exhibited electrophysiological abnormalities both in vitro and in vivo. The atrial cardiomyocyte cell line HL-1 stably expressing delE933 α-MHC showed a significantly slower conduction velocity on multielectrode array than those of wild-type α-MHC or control plasmid transfected cells. Furthermore, targeted morpholino knockdown of MYH6 in zebrafish significantly reduced the heart rate, which was rescued by coexpressed wild-type human α-MHC but not by delE933 α-MHC.

CONCLUSIONS

The novel MYH6 mutation delE933 causes both structural damage of the sarcomere and functional impairments on atrial action propagation. This report reinforces the relevance of MYH6 for sinus node function and identifies a novel pathophysiology underlying familial sick sinus syndrome.