Severe Hypertrophic Cardiomyopathy Research Articles

Left atrial remodeling postseptal myectomy for severe obstructive hypertrophic cardiomyopathy: Analysis by two-dimensional speckle-tracking echocardiography.

Septal myectomy relieves left ventricular outflow obstruction (LVOTO) and is associated with excellent long-term outcomes. LVOTO is associated with diastolic dysfunction and increased left atrial (LA) size. We sought to investigate the changes in LA volumes and function postmyectomy and the association between these changes with clinical outcomes postmyectomy. Sixty-six hypertrophic cardiomyopathy patients undergoing myectomy were retrospectively studied. Preprocedural and 6- to 18-month postmyectomy follow-up transthoracic echocardiographic images were obtained. LA volumes and strain were assessed by two-dimensional speckle-tracking echocardiography. Left atrial volumes, that is, indexed maximal, minimal, and pre-A volumes reduced postmyectomy, yet remained increased compared to controls (105.6±34.5mL vs 84.9±26.7mL, 45.2±25.7mL vs 35.4±22.6mL, 70.1±31.4mL vs 35.4±22.6mL, respectively, P<0.05). The total emptying index did not improve postmyectomy and remained lower than controls (58.6±12.4 vs 59.9±12.8, P=NS) whereas atrial contraction improved, yet did not normalize (active emptying index 36.1±14.9 vs 41.1±16.2, P<0.05). The conduit volume remained reduced postmyectomy (18.6±13.3mL vs 16.6±15.1mL, P=NS). LA strain also did not improve postmyectomy (26.8±7.3 vs 28.5±8.8, P=NS). A multivariable logistic regression identified preprocedural E/e' ratio and indexed maximal LA volume, as independent predictors for LA volume reduction ≥20% postmyectomy. During a mean follow-up of 4.9±2.3 years postmyectomy, 24.2% of the patients developed atrial fibrillation and <5% of patients were severely symptomatic. We found no associations between LA volumes/function and atrial fibrillation or symptoms postmyectomy. Postmyectomy LA volumes decreased, and the contractile function improved. There was no association between LA volumes/function and clinical outcomes postmyectomy. Notably, the LA remained enlarged (though to a lesser degree) with reduced strain and emptying fraction, suggesting possible atrial myopathy.

Multiple structural cardiac malformations in a macrosomic, possibly missed infant of a diabetic mother

Infants of diabetic mothers are prone to cardiac malformations due to teratogenicity of diabetes mellitus (DM). We present here the case of a macrosomic neonate who had marked difficulty with breathing. He had severe hypertrophic cardiomyopathy with patent ductus arteriosus and cor triatriatum dexter, and although his mother had obstetric and a family history suggestive of DM, this diagnosis was not made as her antenatal fasting plasma glucose assay was normal. The need for adequate diagnosis using oral glucose tolerance test or hemoglobin A1c is hereby emphasized.

Hypertrophic Cardiomyopathy Patients With Paroxysmal Atrial Fibrillation Have a High Burden of Left Atrial Fibrosis by Cardiac Magnetic Resonance Imaging.

This study hypothesized that paroxysmal atrial fibrillation (PAF) reflects the presence of a more severe cardiac hypertrophic cardiomyopathy (HCM) phenotype. HCM is characterized by myocyte hypertrophy, fibrosis, and a high prevalence of PAF. It is currently unresolved whether atrial fibrillation (AF) is a marker or a mediator of adverse outcomes in HCM. This study retrospectively examined 45 HCM patients who underwent cardiovascular magnetic resonance (CMR) imaging in sinus rhythm. The function of all 4 cardiac chambers was assessed, as well as late gadolinium enhancement (LGE) in the left atrium (LA) and left ventricle (LV), as indicators of fibrosis. A fat-saturated, 3-dimensional inversion recovery-prepared, fast-spoiled, gradient-recalled echo sequence, and the image intensity ratio method wereused to measure LA-LGE; LGE in the LV was quantified using a semi-automated threshold technique. HCM patients (n= 45) were divided into 2 groups (PAF, no AF) based on history of PAF. All HCM patients hadLGE in the LA posterior wall. The PAF group (n= 18) had higher LA volume, a lower LA ejection fraction, a lower global peak longitudinal LA strain (PLAS), and a higher amount of LA-LGE compared with the no AF group (n= 27). Amodest inverse association was noted between the LA ejection fraction, PLAS, and LA-LGE; a positive association was present between LV-LGE and LA-LGE. The PAF group had lower ejection fractions in the LV, right atrium, and right ventricle compared with those in the no AF group. PAF is associated with a greater degree of structural LA remodeling and global myopathy, whichsuggests a more severe cardiac HCM phenotype.

A novel compound heterozygous mutation in VARS2 in a newborn with mitochondrial cardiomyopathy: a case report of a Chinese family

BackgroundGenetic defects in the mitochondrial aminoacyl-tRNA synthetase are important causes of mitochondrial disorders. VARS2 is one of the genes encoding aminoacyl-tRNA synthetases. Recently, an increasing number of pathogenic variants of VARS2 have been reported.Case presentationWe report the novel compound heterozygous pathogenic VARS2 mutations c.643 C > T (p. His215Tyr) and c.1354 A > G (p. Met452Val) in a female infant who presented with poor sucking at birth, poor activity, hyporeflexia, hypertonia, persistent pulmonary hypertension of newborn (PPHN), metabolic acidosis, severe lactic acidosis, expansion and hypertrophic cardiomyopathy. These heterozygous mutations were carried individually by the proband’s parents and elder sister; the two mutations segregated in the family and were the cause of the disease in the proband.The c.643 C > T (p. His215Tyr) mutation was not described in the ExaC, GNomAD and 1000 Genomes Project databases, and the frequency of c.1354 A > G (p. Met452Val) was < 0.001 in these gene databases.The two mutated amino acids were located in a highly conserved region of the VARS2 protein that is important for its interaction with the cognate tRNA. The two missense mutations were predicted by online tools to be damaging and deleterious.ConclusionsOur report expands the spectrum of known pathogenicVARS2 variants associated with mitochondrial disorders in humans.VARS2 deficiency may cause a severe neonatal presentation with structural cardiac abnormalities.

Abstract 17066: Indications for Implantable Cardioverter-Defibrillator Placement in Pediatric Patients With Hypertrophic Cardiomyopathy

Background: Sudden cardiac death (SCD) is the most common cause of death in children and adolescents with hypertrophic cardiomyopathy (HCM). Implantable cardio-defibrillators (ICD) are highly effective in preventing SCD, however, indications for ICD placement in the young is mainly guided from the adult experience. Methods: We conducted a retrospective single institution study of all children with HCM who had an ICD implanted from July 1999 through February 2016. Results: Thirty-three patients were identified. The mean age at ICD placement was 12.3±3 years with a mean follow up of 3.6±2.5 years. The mean maximal septal wall thickness Z score was 9.3± 2.9 and mean peak LV outflow tract gradient 17±12 mmHg. The median number of indications for ICD placement per patient was 3 (21%, 52%, 15% and 12% of the patients had 2, 3, 4 and 5 indications respectively). The most common indications were: severe HCM (Z-score ≥ + 6) (84%), abnormal blood pressure response to exercise (51%) and late gadolinium enhancement (LGE) (27%). Using the European Society of Cardiology HCM SCD risk calculator, the 5-year SCD risk was highest when the indication was ventricular tachycardia (VT). However, no patient with VT received ICD therapy (shock or anti tachycardia pacing (ATP)) during the study period. Fifteen patients received ICD therapy; 73% appropriately (73% a shock, 9% ATP and 18% both). Inappropriate shocks were delivered to 67% of the patients. One patient had slow rate VT (below the therapy zone) and one patient had ventricular fibrillation that did not elicit ICD therapy and required external defibrillation. The incidence rate ratios for appropriate ICD therapy were higher when the indication for the ICD placement was LGE (3.69), severe HCM (2.3) or compound heterozygosity (1.2) p &lt;0.05. The majority of patients (&gt;95%) were alive and free of transplant at 1 and 5 years after ICD placement. Conclusions: The risk stratification and selection of patients for ICD placement in the pediatric population is challenging. LGE, severe HCM and compound heterozygosity are associated with higher rate of appropriate ICD therapy. Optimal functioning of the ICD device in children and adolescents is difficult. The overall immediate survival and freedom from transplant is excellent.

Loss of embryonic neural crest derived cardiomyocytes causes adult onset hypertrophic cardiomyopathy in zebrafish

Neural crest cells migrate to the embryonic heart and transform into a small number of cardiomyocytes, but their functions in the developing and adult heart are unknown. Here, we show that neural crest derived cardiomyocytes (NC-Cms) in the zebrafish ventricle express Notch ligand jag2b, are adjacent to Notch responding cells, and persist throughout life. Genetic ablation of NC-Cms during embryogenesis results in diminished jag2b, altered Notch signaling and aberrant trabeculation patterns, but is not detrimental to early heart function or survival to adulthood. However, embryonic NC-Cm ablation results in adult fish that show severe hypertrophic cardiomyopathy (HCM), altered cardiomyocyte size, diminished adult heart capacity and heart failure in cardiac stress tests. Adult jag2b mutants have similar cardiomyopathy. Thus, we identify a cardiomyocyte population and genetic pathway that are required to prevent adult onset HCM and provide a zebrafish model of adult-onset HCM and heart failure.

Abstract 498: Functional Annotation of TNNT2 Variants of Uncertain Significance With Induced Pluripotent Stem Cell-derived Cardiomyocytes

The introduction of clinical sequencing is dramatically increasing the discovery of variants of uncertain significance (VUSs) in genes linked to inherited cardiomyopathies. We have established a platform for rapid and efficient insertion of TNNT2 gene variants into an induced pluripotent stem cell (iPSC) line to generate an allelic series of isogenic clones for differentiation into cardiomyocytes (iPSC-CMs) for functional annotation of the variants. We first used CRISPR-Cas9 to introduce known pathogenic variants into iPSCs from a healthy person or to correct pathogenic variants in iPSCs from patients with severe cardiomyopathy. Whereas normal/corrected iPSC-CMs responded to isoproterenol treatment with a 50%-70% increase in spontaneous beating rate as assessed by patch-clamp studies, iPSC-CMs with pathogenic variants had minimal responses (close to 0%). Due to the inefficiency of CRISPR-Cas9 in introducing/correcting variants in iPSCs, we next used dual integrase cassette exchange (DICE) to allow for the introduction of a large number of variants in parallel into a pool of cells. In a single pilot use of the DICE platform, we isolated heterozygous clones with 14 unique variants, &gt;10% of all TNNT2 coding variants cataloged in ClinVar. We found that iPSC-CMs with any of 7 VUSs or likely pathogenic variants were impaired in their response to isoproterenol, in contrast to control DICE-treated iPSC-CMs. Finally, we sought to apply the DICE platform to a patient case in real time. A 65-year-old woman with severe hypertrophic cardiomyopathy underwent gene panel testing that identified a single VUS, TNNT2 E251D. Between the first and second clinic visits (~10 weeks), we were able to use DICE to rapidly and efficiently generate iPSC-CMs with the E251D variant and determine they had normal responses to isoproterenol, suggesting that the variant is not pathogenic. Guided by this finding, we recommended that the patient’s children and grandchildren not undergo cascade genetic screening for the E251D variant. In conclusion, this work establishes the feasibility of rapid functional annotation of cardiomyopathy gene variants, which after further validation could be incorporated into clinical practice as a line of evidence to support variant classification.

Whole-exome sequencing identifies rare compound heterozygous mutations in the MYBPC3 gene associated with severe familial hypertrophic cardiomyopathy

Most patients with hypertrophic cardiomyopathy have single-gene autosomal dominant mutations in loci that encode for sarcomeric proteins. The aim of this study was to determine whether pathogenic mutations were present by whole-exome sequencing (WES) in two families with hypertrophic cardiomyopathy (HCM) that presented during adolescence. Blood samples and clinical data were collected from individuals in two families with HCM. DNA was extracted. Mutations were identified using whole-exome sequencing (WES), and the genotypes of family members were identified using Sanger sequencing. Compound heterozygous mutations in the MYBPC3 gene (c.659A > G, p.Tyr220Cys; c.772G > A, p.Glu258Lys,NM_000256, Family 1), (c.873delG, p. Ile292PhefsTer8; c.3G > A, p.Met1?, NM_000256, Family 2) were identified by WES. Patient 1 carried the maternally inherited c.659A > G mutation and the paternally inherited c.772G > A mutation. Patient 2 carried the maternally inherited frameshift mutation c.873delG and the paternally inherited mutation c.3G > A. Two families with HCM presenting during adolescence (age of onset is about 11 years old) demonstrated compound heterozygous mutations in the MYBPC3 gene. These findings suggested an association of MYBPC3 mutations with the early onset of symptoms and worsened prognoses. Our study highlights the importance of genetic screening of all family members in cases of HCM.

Mitochondrial Dysfunctions Contribute to Hypertrophic Cardiomyopathy in Patient iPSC-Derived Cardiomyocytes with MT-RNR2 Mutation.

SummaryHypertrophic cardiomyopathy (HCM) is the most common cause of sudden cardiac death in young individuals. A potential role of mtDNA mutations in HCM is known. However, the underlying molecular mechanisms linking mtDNA mutations to HCM remain poorly understood due to lack of cell and animal models. Here, we generated induced pluripotent stem cell-derived cardiomyocytes (HCM-iPSC-CMs) from human patients in a maternally inherited HCM family who carry the m.2336T>C mutation in the mitochondrial 16S rRNA gene (MT-RNR2). The results showed that the m.2336T>C mutation resulted in mitochondrial dysfunctions and ultrastructure defects by decreasing the stability of 16S rRNA, which led to reduced levels of mitochondrial proteins. The ATP/ADP ratio and mitochondrial membrane potential were also reduced, thereby elevating the intracellular Ca2+ concentration, which was associated with numerous HCM-specific electrophysiological abnormalities. Our findings therefore provide an innovative insight into the pathogenesis of maternally inherited HCM.

Hypertrophic cardiomyopathy mutation R58Q in the myosin regulatory light chain perturbs thick filament-based regulation in cardiac muscle

Hypertrophic cardiomyopathy (HCM) is frequently linked to mutations in the protein components of the myosin-containing thick filaments leading to contractile dysfunction and ultimately heart failure. However, the molecular structure-function relationships that underlie these pathological effects remain largely obscure. Here we chose an example mutation (R58Q) in the myosin regulatory light chain (RLC) that is associated with a severe HCM phenotype and combined the results from a wide range of in vitro and in situ structural and functional studies on isolated protein components, myofibrils and ventricular trabeculae to create an extensive map of structure-function relationships. The results can be understood in terms of a unifying hypothesis that illuminates both the effects of the mutation and physiological signaling pathways. R58Q promotes an OFF state of the thick filaments that reduces the number of myosin head domains that are available for actin interaction and ATP utilization. Moreover this mutation uncouples two aspects of length-dependent activation (LDA), the cellular basis of the Frank-Starling relation that couples cardiac output to venous return; R58Q reduces maximum calcium-activated force with no significant effect on myofilament calcium sensitivity. Finally, phosphorylation of R58Q-RLC to levels that may be relevant both physiologically and pathologically restores the regulatory state of the thick filament and the effect of sarcomere length on maximum calcium-activated force and thick filament structure, as well as increasing calcium sensitivity. We conclude that perturbation of thick filament-based regulation may be a common mechanism in the etiology of missense mutation-associated HCM, and that this signaling pathway offers a promising target for the development of novel therapeutics.

Case report: Leopard syndrome in a newborn with severe hypertrophic cardiomyopathy

Case report: Leopard syndrome in a newborn with severe hypertrophic cardiomyopathy

Biventricular Hypertrophic Cardiomyopathy in a Child with LEOPARD Syndrome: a Case Report

Abstract Background: LEOPARD syndrome is a complex dysmorphogenetic disorder of inconstant penetrance and various morphologic expressions. The syndrome is an autosomal dominant disease that features multiple lentigines, electrocardiographic changes, eye hypertelorism, pulmonary valve stenosis or hypertrophic cardiomyopathy, genital malformations, and a delayed constitutional growth hearing loss, which can be associated with rapidly progressive severe biventricular obstructive hypertrophic cardiomyopathy. No epidemiologic data are available on the real incidence of LEOPARD syndrome; however, this seems to be a rare disease, being often underdiagnosed, as many of its features are mild. Case presentation: We report the case of a 10-year-old female pediatric patient, diagnosed with obstructive hypertrophic cardiomyopathy at the age of 3 months, and recently diagnosed with LEOPARD syndrome. The patient first presented for a cardiologic examination at the age of 3 months, due to a murmur. She presented failure to thrive and psychomotor retardation, and was diagnosed with biventricular obstructive hypertrophic cardiomyopathy for which she had received high-dose beta-blocker therapy. At the age of 7 years she underwent a biventricular myectomy for relief of outflow tract obstruction, completed with another myectomy after 2 years due to progressive increase of pressure gradient in the left ventricular outflow tract. Prior to the second surgical intervention, multiple lentigines appeared on her skin, and genetic testing revealed the presence of LEOPARD syndrome. Conclusion: LEOPARD syndrome is a rare disease, which can be very difficult to diagnose, especially based on features other than lentigines. Cardiac involvement in LEOPARD syndrome can be progressive and requires multiple medical and surgical interventions.

Clinical long-term outcome of septal myectomy for obstructive hypertrophic cardiomyopathy in infants.

Surgical septal myectomy is performed to relieve left ventricular outflow tract narrowing in severe drug-refractory obstructive hypertrophic cardiomyopathy. The objective of this study was to assess the perioperative and long-term clinical outcome of this procedure performed during infancy. Clinical, transthoracic echocardiographic, electrocardiographic, 24-h Holter, cardiopulmonary exercise test and genetic data were extracted by medical record review. A subset of patients underwent additional prospective detailed clinical evaluation including cardiac magnetic resonance imaging with contrast. Surgery was performed in 23 paediatric patients between 1978 and 2015 at the German Heart Centre Munich. Twelve patients had undergone surgery during infancy (≤ 1 year) (Group A), 11 between 1 and 18 years of age (Group B). The underlying genetic diagnosis was Noonan syndrome spectrum and non-syndromic hypertrophic cardiomyopathy. As compared to Group B, patients in Group A showed more concomitant cardiac procedures and received more homologous transfusions. One perioperative death occurred in Group A, and none in Group B. Two patients in Group A but no patient in Group B required redo septal myectomy. The long-term clinical outcome was similar between the 2 groups. One patient in Group B required cardioverter-defibrillator/pacemaker implantation for higher degree atrioventricular block and none in Group A. There was no evidence of differences in myocardial fibrosis between groups on long-term follow-up magnetic resonance imaging. Surgical septal myectomy can be performed safely during infancy with favourable perioperative and long-term clinical outcome but with a trend towards a higher reoperation rate later in life.

Persistently elevated nuchal translucency and the fetal heart

Objective: To describe the outcome of fifteen cases with an elevated nuchal translucency (NT) which persisted into the second trimester as nuchal edema (NE) >6 mm whom underwent fetal echocardiography. Materials and methods: Cases were identified following retrospective review of cardiac and genetic findings in fetuses with NE. Results: Minor congenital heart disease was identified in 3/15 by the second trimester. Agenesis of the ductus venosus was evident in four. Pulmonary valve stenosis was diagnosed in one fetus at the 20-week scan and hypertrophic cardiomyopathy in one. However, hypertrophic cardiomyopathy or pulmonary valve stenosis was present after birth in all surviving cases by 3 months of age. On the basis of intention to treat, 11/12 survived to delivery and 9/12 survived to 28 days. There were 6 deaths before 14 months of age as a result of severe hypertrophic cardiomyopathy. Noonan syndrome was confirmed with genetic testing in 11/15 cases. Conclusions: All fetuses with NT and NE had evidence of congenital heart disease at birth, and therefore, late gestation and postnatal review is recommended even when second trimester echocardiogram is considered normal. There is a high prevalence of Noonan syndrome and targeted genetic analysis should be considered. The outcome in these cases is poor.

The Phenotype and Outcome of Infantile Cardiomyopathy Caused by a Homozygous ELAC2 Mutation

Objective: Cardiomyopathy (CMP) in children is a clinically and genetically heterogeneous group of disorders. Disease-associated mutations have been identified in more than 50 genes. Recently, mutations in the mitochondrial tRNA processing gene, ELAC2, were reported to be associated with the recessively inherited form of hypertrophic CMP (HCM). This study is aimed at describing the cardiac phenotype and outcome of ELAC2 mutation. Methods: We performed whole exome sequencing followed by targeted mutation screening to identify the genetic etiology of severe infantile-onset CMP in 64 consanguineous Saudi families. Results: A previously reported mutation (p.Phe154Leu) in ELAC2 gene was detected in 16 families. The index cases presented between 2 and 7 months of age with HCM in 13 infants and dilated CMP (DCM) in 3. Pericardial effusion was observed in 7 infants (44%). All infants died with a median age of death of 4 months. Almost 1/3 of them died during the initial presentation. Conclusion: Our study suggests screening the ELAC2 gene in severe infantile-onset HCM or DCM of unknown etiology, especially in the presence of pericardial effusion. Our work demonstrates a universally poor outcome of the (p.Phe154Leu) variant in ELAC2 gene; a correlation that helps in counseling parents and in planning appropriate medical intervention.

Three patients presenting with severe macrosomia and congenital hypertrophic cardiomyopathy: a case series

BackgroundMacrosomia and hypertrophic cardiomyopathy are two features often associated in neonates of diabetic mothers. We report the cases of three patients with severe macrosomia and critical hypertrophic cardiomyopathy without severely unbalanced maternal diabetes. Only three patients with those two features and no uncontrolled maternal diabetes have been previously reported.Case presentationThe first patient was a 39-week-old girl, the second patient was a 39-week-old girl, and the third patient was a 41-week-old boy. The two French girls and the French boy had severe macrosomia and hypertrophic cardiomyopathy, leading to the death of the boy. The outcome of the two girls was favorable, with a standardization of growth curves and ventricular hypertrophy. Their mothers presented with high body mass index but no severe documented maternal diabetes; glycemic imbalance was only suspected on postnatal analyses. There was no hydramnios during pregnancy and no other environmental factor, especially toxic exposure. Their parents are from Mayotte, Guadeloupe, and Guinea-Conakry. The usual genetics causes, Beckwith–Wiedemann syndrome, and chromosomal copy number variation, were also excluded.ConclusionsThis report suggests the implication of other factors in addition to glycemic disorders, including genetic factors, in the occurrence of macrosomia and severe hypertrophic cardiomyopathy in neonates. These three original observations indicate that gynecologists and neonatologists should pay attention to neonates from mothers with a high body mass index and when maternal diabetes is not documented.

Cardiac response to enzyme replacement therapy in infantile Pompe disease with severe hypertrophic cardiomyopathy

Classic infantile-onset Pompe disease (IOPD), characterized by predominantly cardiac involvement, used to be considered uniformly lethal within months. The availability of enzyme replacement therapy (ERT) has transformed the course of the disease. Decrease in ventricular hypertrophy and improvement in ventricular function have been suggested as proof for efficacy. We report the cardiac response to ERT of a child with IOPD and severe hypertrophic cardiomyopathy. The myocardial hypertrophy resolved. Change in ejection fraction, however, was slow. We discuss the potential benefit of other parameters beyond ejection to assess cardiac function in IOPD, including speckle tracking-based strain.

Abstract 12739: Gap Junction Protein Beta 4 Plays an Important Role In Cardiac Hypertrophy and Cardiac Function in Human and Zebrafish

Introduction: Gap junction protein beta 4 (GJB4) encodes a transmembrane connexin protein (Cx30.3) that is a component of gap junctions. Mutations in this gene remain unknown to be associated with hypertrophic cardiomyopathy (HCM) and cardiac dysfunction. Hypothesis: Our hypothesis is that mutations in GJB4 can cause familial HCM, which can progresses into dilated-phase HCM (d-HCM). Methods: We have previously examined a patient and her elder brother who both presented with complicated severe HCM and whose parents are married cousins. The elder brother had died suddenly as a child and the autopsy demonstrated the development of HCM. The patient was diagnosed with HCM, which progressed to d-HCM during the 20-year follow-up. The patient has recently undergone cardiac transplantation. The parents are healthy. We hypothesized that an autosomal recessive mutation caused their familial HCM. The whole-exome sequencing was performed from each of the three participants. We generated knockout zebrafish of GJB4 and ELP2 by CRISPER/Cas9 system and analysis the volume and function of ventricle at five days post fertilization (dpf). Results: The gene exome analysis showed 34 single nucleotide polymorphisms (SNPs) that caused amino acid change for which the patient was homozygous and both parents were heterozygous after excluding all known common (&gt;10%) SNP gene mutations in the dbSNP. Among them, GJB4 and ELP2 were the identified genes that are possibly associated with cardiac muscle. The PolyPhen-2 scores of mutations in GJB4 and ELP2 were 1.000 and 0.001 respectively. The identified missense mutation was a 981 A&gt;C nucleotide transition in GJB4. The resultant E204A substitution replaces a polar carboxylic glutamate with a nonpolar alanine. The endodiastolic volume was significantly lower in GJB4-KO (94pl, p&lt;0.01) and ELP2-KO (95pl, p&lt;0.01) than in wild type (WT, 145pl) zebrafish at 5 dpf. Furthermore the ventricular ejection fraction was decreased in GJB4 KO (0.66, p&lt;0.01) and unchanged in ELP2-KO (0.80) respectively compared with WT zebrafish (0.82). Conclusions: These results indicate both that mutations in GJB4 and ELP2 can cause a familial form of HCM and that GJB4 especially may be a new target for treatment of cardiac function and hypertrophy.

Impact of disease-causing mutations on inter-domain interactions in cMyBP-C: a steered molecular dynamics study

The molecular interactions of the sarcomeric proteins are essential in the regulation of various cardiac functions. Mutations in the gene MYBPC3 coding for cardiac myosin-binding protein-C (cMyBP-C), a multi-domain protein, are the most common cause of hypertrophic cardiomyopathy (HCM). The N-terminal complex, C1-motif-C2 is a central region in cMyBP-C for the regulation of cardiac muscle contraction. However, the mechanism of binding/unbinding of this complex during health and disease is unknown. Here, we study possible mechanisms of unbinding using steered molecular dynamics simulations for the complex in the wild type, in single mutations (E258K in C1, E441K in C2), as well as in a double mutation (E258K in C1 + E441K in C2), which are associated with severe HCM. The observed molecular events and the calculation of force utilized for the unbinding suggest the following: (i) double mutation can encourage the formation of rigid complex that required large amount of force and long-time to unbind, (ii) C1 appears to start to unbind ahead of C2 regardless of the mutation, and (iii) unbinding of C2 requires larger amount of force than C1. This molecular insight suggests that key HCM-causing mutations might significantly modify the native affinity required for the assembly of the domains in cMyBP-C, which is essential for normal cardiac function.

Transplantation combinée cœur–rein au cours de la maladie de Fabry : suivi à long terme de deux patients

IntroductionFabry disease is a lysosomal storage disorder linked to an alpha-galactosidase A deficiency that can lead to heart and kidney failure. There is little data about the prognosis of patients who undergo a combined heart and kidney transplantation. Case reportsTwo brothers who were diagnosed with Fabry disease after the age of 30 years underwent a combined heart and kidney transplantation at respectively 49 and 42 years of age because of a severe hypertrophic cardiomyopathy with end stage renal failure. They are alive respectively 4 and 9 years after the transplantation. No recurrence of the disease in the transplanted organs has been found. ConclusionCombined heart and kidney transplantation in Fabry disease is an efficient therapy for the cardiomyopathy and kidney failure. Its prognosis can be good when the patients are carefully selected. However, an early diagnosis is critical in order to avoid a procedure associated with a high perioperative mortality.