Aldosterone, Through Novel Signaling Proteins, Is a Fundamental Molecular Bridge Between the Genetic Defect and the Cardiac Phenotype of Hypertrophic Cardiomyopathy

Abstract Introduction Hypertrophic cardiomyopathy (HCM) is a progressive disease characterized by cardiac remodeling, hyperdynamic contraction, and impaired ventricular filling that can lead to dynamic left-ventricular outflow-track (LVOT) obstruction and exertional intolerance. Direct myosin-inhibition with mavacamten can normalize contractility and improve exercise capacity in patients with oHCM, providing sustained symptomatic relief. However, mavacamten can also improve ventricular filling by limiting residual cross-bridges during diastole, and therefore, may offer cardiac benefits beyond obstruction reprieve. This study leveraged a feline model of oHCM, cats with the A31P MYBPC3 variant, to study the acute in vivo effects of MYK-581, a mavacamten surrogate, on cardiac hemodynamics and filling. Methods A31P-homozygous cats with HCM (A31P, n=10) and wild-type healthy controls (CTRL, n=9) were anesthetized and instrumented for invasive pressure-volume (PV) measurements as well as trans-thoracic echocardiographic recording. A subset of cats were assigned to receive either vehicle (VEH, n=7) or MYK-581 (MYK, n=8) with a short IV infusion. Cardiac hemodynamics, function, and geometry were assessed at steady state before and during dobutamine challenges (2.5 μg/kg/min IV). Results A31P cats had thicker ventricular walls (6.4±0.1 vs. 5.2±0.2 mm, P<0.05) and hyperdynamic contraction (FS: 61±4 vs. 50±3%, P<0.05) relative to controls and presented with dynamic LVOT obstruction in 54% of cases. HCM cats had elevated end-diastolic pressures (17±1.4 vs. 9±1.0 mmHg, P<0.05), with prolonged time constants of relaxation (60±4.1 vs. 36±2.4 ms, P<0.05) and elevated end-diastolic stiffness (Eed: 0.44±0.06 vs. 0.25±0.01 mmHg/mL). Acute treatment with MYK-581 alleviated LVOT obstruction (0% vs. 38%), normalized contractility (FS: −7±2%), and increased systolic/diastolic chamber dimensions (e.g., LVIDd: +13±4%) (all P<0.05), while reducing EDP (15±2 to 13±2 mmHg, P<0.05), suggesting acute improvement in ventricular distensibility. Indeed, MYK-581 treatment reduced end-diastolic stiffness (Eed: 0.48±0.11 vs. 0.36±0. 10 mmHg/mL, P<0.05) and normalized trans-mitral motion patterns during filling. Conclusions Bred cats, homozygous for the A31P MYBPC3 variant, presented a cardiac phenotype that models multiple characteristics of the human oHCM phenotype including dynamic LVOT obstruction. Acute treatment with the mavacamten surrogate, MYK-581, not only alleviated hypercontractility and LVOT obstruction, but improved ventricular filling and end-diastolic pressures. Taken together, these pre-clinical observations show potential salutary effects beyond obstruction relief in patients with HCM. Funding Acknowledgement Type of funding source: Private company. Main funding source(s): MyoKardia

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Hypertrophic cardiomyopathy-linked variants of cardiac myosin-binding protein C3 display altered molecular properties and actin interaction

Biochemical Journal ◽

10.1042/bcj20180685 ◽

2018 ◽

Vol 475 (24) ◽

pp. 3933-3948 ◽

Cited By ~ 4

Author(s):

Sahar I. Da'as ◽

Khalid Fakhro ◽

Angelos Thanassoulas ◽

Navaneethakrishnan Krishnamoorthy ◽

Alaaeldin Saleh ◽

...

Keyword(s):

Hypertrophic Cardiomyopathy ◽

Binding Protein ◽

Clinical Severity ◽

Actin Binding ◽

Cardiac Myosin ◽

C2 Domains ◽

Cardiac Phenotype ◽

Myosin Binding Protein ◽

Myosin Binding ◽

The Impact

The most common inherited cardiac disorder, hypertrophic cardiomyopathy (HCM), is characterized by thickening of heart muscle, for which genetic mutations in cardiac myosin-binding protein C3 (c-MYBPC3) gene, is the leading cause. Notably, patients with HCM display a heterogeneous clinical presentation, onset and prognosis. Thus, delineating the molecular mechanisms that explain how disparate c-MYBPC3 variants lead to HCM is essential for correlating the impact of specific genotypes on clinical severity. Herein, five c-MYBPC3 missense variants clinically associated with HCM were investigated; namely V1 (R177H), V2 (A216T), V3 (E258K), V4 (E441K) and double mutation V5 (V3 + V4), all located within the C1 and C2 domains of MyBP-C, a region known to interact with sarcomeric protein, actin. Injection of the variant complementary RNAs in zebrafish embryos was observed to recapitulate phenotypic aspects of HCM in patients. Interestingly, V3- and V5-cRNA injection produced the most severe zebrafish cardiac phenotype, exhibiting increased diastolic/systolic myocardial thickness and significantly reduced heart rate compared with control zebrafish. Molecular analysis of recombinant C0–C2 protein fragments revealed that c-MYBPC3 variants alter the C0–C2 domain secondary structure, thermodynamic stability and importantly, result in a reduced binding affinity to cardiac actin. V5 (double mutant), displayed the greatest protein instability with concomitant loss of actin-binding function. Our study provides specific mechanistic insight into how c-MYBPC3 pathogenic variants alter both functional and structural characteristics of C0–C2 domains leading to impaired actin interaction and reduced contractility, which may provide a basis for elucidating the disease mechanism in HCM patients with c-MYBPC3 mutations.

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P1771Right ventricular mechanical changes after septal myectomy for obstructive hypertrophic cardiomyopathy. Vector velocity imaging study

European Heart Journal ◽

10.1093/eurheartj/ehz748.0523 ◽

2019 ◽

Vol 40 (Supplement_1) ◽

Author(s):

H Badran ◽

G Soltan ◽

N Faheem ◽

M Ezzat ◽

M H Yacoub

Keyword(s):

Hypertrophic Cardiomyopathy ◽

Nyha Class ◽

Imaging Study ◽

Functional Class ◽

Class Iii ◽

Septal Myectomy ◽

Cardiac Phenotype ◽

Velocity Imaging ◽

Vector Velocity ◽

Surgical Myectomy

Abstract Objectives The impairment of right ventricular (RV) myocardial mechanics is evident in hypertrophic cardiomyopathy (HCM). It is independently influenced by LV mechanics and correlated to the severity of LV phenotype. We investigated the changes in RV global and regional deformation following surgical septal myectomy using vector velocity imaging (VVI). Methods 25 HCM patients, 68% males with mean age (34.5±12 years) were examined before and within two months after surgical myectomy using VVI. In addition to conventional echocardiographic parameters, peak systolic strain (εsys), strain rate (SR) and time to peak εsys (TTP) of regional RV free wall (RVFW) & septal walls were analyzed in longitudinal (long) directions from apical four chamber view and their (Δ)changes were calculated. Similar parameters were quantified in LV from apical 2 & 4 CH views. Intra-V-delay was defined as SD of TTP and inter-V dyssynchrony was estimated from TTP difference between the most delayed LV segment & RVFW. Results All study patients showed improvement of their functional class from NYHA class III to class I and reduction of LVOT gradient to below 20 mmHg except one patient who had 30 mmHg gradients at rest. There was significant reduction of septal thickness, left atrial diameter& volume, LVOT gradient, LVMI, severity of mitral regurgitation, tricuspid annular velocities (P<0.0001), RV diameter (P<0.02) and increase in LV internal dimensions (P<0.001) post myectomy. However, there was significant reduction of RV and LV systolic mechanics; RV global εsys % (from −16.1±4.4 to −12.9±2.9, P<0.0001) and LV global εsys %: from −11.6±2.8 to −9.4±2.2%, P<0.0001) respectively. The magnitude of reduction of RV strain (Δ RV εsys%, Δ SRsys) was directly correlated LV maximal wall thickness (r=0.46, P<0.01) and ΔRV dyssynchrony (TTP-SD), (r=0.4, P<0.05) and negatively correlated to age (r=−0.46, P<0.02), pre-op RV SRsys (r=−0.52, P<0.01) and pre-op LV EF% (r=−0.43, P<0.03). Meanwhile the reduction in RV diastolic mechanics: Δ RV SRe & SRa were directly correlated to PAP and LVOT gradient before surgery (r=0.62, P<0.002). Conclusion Despite improvement of patient functional status and reduction LVOT gradient, RV mechanics shows further deterioration after surgical myectomy. The magnitude of reduction is modestly related to cardiac phenotype and pre-op mechanical function.

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Severe cardiac phenotype in a double-mutant model of familial hypertrophic cardiomyopathy (FHC)

Journal of Molecular and Cellular Cardiology ◽

10.1016/j.yjmcc.2007.03.438 ◽

2007 ◽

Vol 42 (6) ◽

pp. S167-S168

Author(s):

T. Tsoutsman ◽

M. Kelly ◽

E. Tu ◽

L. Lam ◽

C.E. Seidman ◽

...

Keyword(s):

Hypertrophic Cardiomyopathy ◽

Double Mutant ◽

Familial Hypertrophic Cardiomyopathy ◽

Cardiac Phenotype

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The relation of ventricular arrhythmia electrophysiological characteristics to cardiac phenotype and circadian patterns in hypertrophic cardiomyopathy

EP Europace ◽

10.1093/europace/eur362 ◽

2011 ◽

Vol 14 (5) ◽

pp. 724-733 ◽

Cited By ~ 25

Author(s):

Constantinos O'Mahony ◽

Pier D. Lambiase ◽

Shafiqur M. Rahman ◽

Montserrat Cardona ◽

Margherita Calcagnino ◽

...

Keyword(s):

Hypertrophic Cardiomyopathy ◽

Ventricular Arrhythmia ◽

Cardiac Phenotype ◽

Circadian Patterns

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Abstract 1427: Pathogenesis of Hypertrophic Cardiomyopathy Caused by the Myozenin 2 Mutations Involves Calcineurin-Dependent and -Independent Mechanisms

Circulation ◽

10.1161/circ.118.suppl_18.s_323-c ◽

2008 ◽

Vol 118 (suppl_18) ◽

Author(s):

Suet Nee Chen ◽

Raffaella Lombardi ◽

Gabriela Rodriguez ◽

Ali J Marian

Keyword(s):

Hypertrophic Cardiomyopathy ◽

Cardiac Hypertrophy ◽

Interstitial Fibrosis ◽

Systolic Function ◽

Inhibitory Effect ◽

Loss Of Function ◽

Activated T Cells ◽

Downstream Target ◽

Cardiac Phenotype ◽

Calcineurin Phosphatase

Identification of myozenin-2 mutations (MYOZ2) has expanded the spectrum of causal mutations for hypertrophic cardiomyopathy (HCM) to include the Z disk proteins. The molecular mechanism(s) by which MYOZ2 mutations cause HCM are unknown. MYOZ2 is known to inhibit calcineurin phosphatase (PP2B). We posit mutant MYOZ2 lose their inhibitory effects on PP2B and hence, the ensuing cardiac phenotype results from enhanced activity of PP2B. To test this hypothesis, we generated lines of transgenic mice expressing either N-terminally flag-tagged wild type (MYOZ2-WT) or mutant MYOZ2-P48 or MYOZ2-M246 regulated by the α-myosin heavy chain promoter. Expression levels of the transgenic and endogenous MYOZ2 proteins were detected by immunoblotting using pan-specific anti-MYOZ2 and anti-Flag antibodies. The transgene proteins constituted 15 to 35% of the total MYOZ2 protein. The total MYOZ2 levels remained unchanged. Immunofluorescence staining showed both WT and mutant MYOZ2 proteins were incorporated into the Z disks. To determine the effects of the WT and mutant MYOZ2 proteins on PP2B activity, we measured PP2B phosphatase and Nuclear Factor of Activated T Cells (NFATc), a downstream target of PP2B, activities in myocardial protein extracts by ELISA-based assays. Expression of MYOZ2-WT reduced PP2B phosphatase and NFAT activities by ~90% and 20%, respectively while equal levels of expression of the mutant MYOZ2 reduced these activities by ~ 50% and 10%, respectively, i.e., a 2-fold reduction in inhibitory effect of the mutant as compared to WT. The mutant MYOZ2-P48 and MYOZ2-M246 showed increased mortality, cardiac hypertrophy, preserved cardiac systolic function, increased myocytes size and interstitial fibrosis. The MYOZ2-WT mice also exhibited cardiac hypertrophy and interstitial fibrosis. Thus, the mutation impart a loss of function effect on MYOZ2, suggesting a possible gain of function of PP2B in humans with with autosomal dominant HCM. However, excess inhibition of PP2B in the heart, as observed in the MYOZ2-WT mice, also led to cardiac hypertrophy and fibrosis. Thus both excess inhibition as well as relative enhancement of PP2B activity in the heart could cause cardiac hypertrophy and fibrosis.

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Sex-specific cardiac phenotype and clinical outcomes in patients with hypertrophic cardiomyopathy

American Heart Journal ◽

10.1016/j.ahj.2019.10.004 ◽

2020 ◽

Vol 219 ◽

pp. 58-69 ◽

Cited By ~ 1

Author(s):

Dai-Yin Lu ◽

Ioannis Ventoulis ◽

Hongyun Liu ◽

Shibani M. Kudchadkar ◽

Gabriela V. Greenland ◽

...

Keyword(s):

Hypertrophic Cardiomyopathy ◽

Clinical Outcomes ◽

Cardiac Phenotype

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Palpitation was associated with clinical outcomes in patients with hypertrophic cardiomyopathy

Scientific Reports ◽

10.1038/s41598-020-71797-y ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Tingting Hu ◽

Tao Wang ◽

Xiwen Zhang

Keyword(s):

Heart Failure ◽

Hypertrophic Cardiomyopathy ◽

Clinical Outcomes ◽

Logistic Analysis ◽

Cardiac Phenotype ◽

Kaplan Meier ◽

Cerebrovascular Events ◽

Heart Failure Exacerbation ◽

And Function ◽

Genetic Heart Disease

Abstract Hypertrophic cardiomyopathy (HCM) is a common genetic heart disease with diversified clinical presentation and it is important to identify new predictors of clinical outcomes and survival in HCM patients. In our study, 206 HCM patients were compared with respect to major adverse cardiovascular and cerebrovascular events. By multivariable logistic analysis, we determined that palpitation, together with chronic heart failure (CHF) > 1 year, was an independent predictor of major adverse cardiovascular and cerebral events (MACCE) in HCM patients (OR 3.24, 95% CI 1.60–6.57, P = 0.001). Specially, palpitation was related to higher prevalence of rehospitalization (OR 3.86, 95% CI 2.08–7.08, P < 0.001), cardiac death (OR 2.96, 95% CI 1.05–8.32, P = 0.04) and heart failure exacerbation (OR 4.07, 95% CI 2.04–8.13, P < 0.001). However, patients presented with palpitation did not show a significantly different cardiac phenotype and function. Finally, palpitation predicted a poor prognosis in HCM patients without atrial fibrillation by utilizing Kaplan–Meier analysis (P = 0.041). In conclusion, palpitation could be a new predictor of clinical outcomes and overall survival in HCM patients.

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Differences in molecular phenotype in mouse and human hypertrophic cardiomyopathy

Scientific Reports ◽

10.1038/s41598-021-89451-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Styliani Vakrou ◽

Yamin Liu ◽

Li Zhu ◽

Gabriela V. Greenland ◽

Bahadir Simsek ◽

...

Keyword(s):

Gene Expression ◽

Hypertrophic Cardiomyopathy ◽

Mouse Models ◽

Pathway Analysis ◽

Intracellular Signaling ◽

Mutant Mice ◽

Disease Stage ◽

Specific Gene ◽

Cardiac Phenotype ◽

Established Disease

AbstractHypertrophic cardiomyopathy (HCM) is characterized by phenotypic heterogeneity. We investigated the molecular basis of the cardiac phenotype in two mouse models at established disease stage (mouse-HCM), and human myectomy tissue (human-HCM). We analyzed the transcriptome in 2 mouse models with non-obstructive HCM (R403Q-MyHC, R92W-TnT)/littermate-control hearts at 24 weeks of age, and in myectomy tissue of patients with obstructive HCM/control hearts (GSE36961, GSE36946). Additionally, we examined myocyte redox, cardiac mitochondrial DNA copy number (mtDNA-CN), mt-respiration, mt-ROS generation/scavenging and mt-Ca2+ handling in mice. We identified distinct allele-specific gene expression in mouse-HCM, and marked differences between mouse-HCM and human-HCM. Only two genes (CASQ1, GPT1) were similarly dysregulated in both mutant mice and human-HCM. No signaling pathway or transcription factor was predicted to be similarly dysregulated (by Ingenuity Pathway Analysis) in both mutant mice and human-HCM. Losartan was a predicted therapy only in TnT-mutant mice. KEGG pathway analysis revealed enrichment for several metabolic pathways, but only pyruvate metabolism was enriched in both mutant mice and human-HCM. Both mutant mouse myocytes demonstrated evidence of an oxidized redox environment. Mitochondrial complex I RCR was lower in both mutant mice compared to controls. MyHC-mutant mice had similar mtDNA-CN and mt-Ca2+ handling, but TnT-mutant mice exhibited lower mtDNA-CN and impaired mt-Ca2+ handling, compared to littermate-controls. Molecular profiling reveals differences in gene expression, transcriptional regulation, intracellular signaling and mt-number/function in 2 mouse models at established disease stage. Further studies are needed to confirm differences in gene expression between mouse and human-HCM, and to examine whether cardiac phenotype, genotype and/or species differences underlie the divergence in molecular profiles.

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Characterisation of cardiac phenotype in genetically defined hypertrophic cardiomyopathy

Journal of Nuclear Cardiology ◽

10.1016/j.nuclcard.2004.12.223 ◽

2005 ◽

Vol 12 (2) ◽

pp. S58-S58

Author(s):

H TUUNANEN ◽

J KUUSISTO ◽

J TOIKKA ◽

P JAASKELAINEN ◽

M HAAPARANTA ◽

...

Keyword(s):

Hypertrophic Cardiomyopathy ◽

Cardiac Phenotype

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