Malignant familial hypertrophic cardiomyopathy in a family with a 453Arg→Cys mutation in the β-myosin heavy chain gene: Coexistence of sudden death and end-stage heart failure

Recent genotype-phenotype correlation studies in familial hypertrophic cardiomyopathy (FHC) have revealed that some mutations in the β-myosin heavy chain (BMHC) gene may be associated with a high incidence of sudden death and a poor prognosis. Coexistence of sudden death and end-stage heart failure in several families with FHC has recently being reported; however, the genetic basis of such families has not been clearly demonstrated. A three-generation Chinese familial hypertrophic cardiomyopathy (FHC) family (family HL1) with two cases of end-stage heart failure and three cases of sudden death was analyzed. The average age of death in the affected members in this family was 34 years old. Genetic linkage analysis using polymorphisms in the α- and β-myosin heavy chain genes revealed that FHC in this family is significantly linked to the BMHC gene without recombinations. Single-strand conformation polymorphism analysis of exons 8, 9 and 13 to 23 in the BMHC gene showed a polymorphic band on exon 14 that is in complete linkage with the disease status in this family. DNA sequencing analysis in the affected members revealed an 453Arg→Cys mutation in the BMHC gene. To our knowledge this is the first reported mutation of FHC in Chinese. Our data suggest that the 453Arg→Cys mutation is associated with a malignant clinical course in FHC due not only to sudden death but also to end-stage heart failure. Received: 6 July 1995 / Revised: 20 September 1995     

No evidence for linkage of familial hypertrophic cardiomyopathy and chromosome 14q1 locus D14S26 in a chinese family: evidence for genetic heterogeneity

Summary To understand the molecular basis of familial hypertrophic cardiomyopathy (FHC) in the Chinese population, a family with FHC was investigated. Nineteen family members who were 16 years of age or older were examined by M-mode or two-dimensional echocardiography. Eight members were diagnosed to be affected echocardiographically or clinically. Lymphocytes isolated from 20 family members were successfully transformed into permanent lymphoblastoid cell lines by Epstein-Barr virus. Three genomic DNA probes (CRI-L436, CRI-L329, and pSC14) that were derived from chromosome 14q1 loci and demonstrated to be linked closely to FHC were used to probe this family. Using the techniques of restriction fragment length polymorphism (RFLP) and linkage analysis, the probe CRI-L436, which recognized locus D14S26, was found informative in this family. The lod scores were -2.0 at = 0.025 and -1.49 at = 0.05. Thus, there was no evidence of linkage between the locus D14S26 and the gene for FHC in the pedigree studied. In addition, polymerase chain reaction (PCR) amplification did not indicate a mutation on exon 13 of the cardiac myosin heavy chain gene as previously reported. Our data suggest that FHC is a genetically heterogeneous disease.     

A locus for familial hypertrophic cardiomyopathy is closely linked to the cardiac myosin heavy chain genes, CRI-L436, and CRI-L329 on chromosome 14 at q11-q12

We report that a gene responsible for familial hypertrophic cardiomyopathy (HC) is closely linked to the cardiac alpha and beta myosin heavy chain (MHC) genes on chromosome 14q11. We have recently shown that probe CRI-L436, derived from the anonymous DNA locus D14S26, detects a polymorphic restriction fragment that segregates with familial HC in affected members of a large Canadian family. Using chromosomal in situ hybridization, we have mapped CRI-L436 to chromosome 14 at q11-q12. Because the cardiac MHC genes also map to this chromosomal band, we have determined the genetic distances between the cardiac beta MHC gene, D14S26, and the familial HC locus. Data presented here show that these three loci are linked within 5 centimorgans on chromosome 14 at q11-q12. The possibility that defects in either the cardiac alpha or beta MHC genes are responsible for familial HC is discussed.     

A molecular basis for familial hypertrophic cardiomyopathy: a beta cardiac myosin heavy chain gene missense mutation

A point mutation in exon 13 of the beta cardiac myosin heavy chain (MHC) gene is present in all individuals affected with familial hypertrophic cardiomyopathy (FHC) from a large kindred. This missense mutation converts a highly conserved arginine residue (Arg-403) to a glutamine. Affected individuals from an unrelated family lack this missense mutation, but instead have an alpha/beta cardiac MHC hybrid gene. Identification of two unique mutations within cardiac MHC genes in all individuals with FHC from two unrelated families demonstrates that defects in the cardiac MHC genes can cause this disease. The pathology resulting from a missense mutation at residue 403 further suggests that a critical function of myosin is disrupted by this mutation.     

Mitochondrial ND5 12338T>C variant is associated with maternally inherited hypertrophic cardiomyopathy in a Chinese pedigree

Hypertrophic cardiomyopathy is a primary disorder characterized by asymmetric thickening of the septum and left ventricular wall, which affects 1 in 500 individuals in the general population. Mutations in mitochondrial DNA have been found to be one of the most important causes of hypertrophic cardiomyopathy. Here we report the clinical, genetic and molecular characterization of a Han Chinese family with a likely maternally transmitted hypertrophic cardiomyopathy. Four (2 men/2 women) of 5 matrilineal relatives in this 3-generation family exhibited the variable severity and age at onset of 44 to 79years old. Sequence analysis of the entire mitochondrial DNA in this pedigree identified the known homoplasmic ND5 12338T>C variant. This mitochondrial DNA haplogroup belongs to the Eastern Asian F2a. The 12338T>C variant, highly evolutionarily conserved, resulted in the replacement of the translation initiating methionine with a threonine, shortening the ND5 polypeptide by 2 amino acids. The occurrence of ND5 12338T>C variant exclusively in maternal members of this Chinese family suggested that the 12338T>C variant is associated with maternally inherited hypertrophic cardiomyopathy. Our findings will provide theoretical basis for genetic counseling of maternally inherited hypertrophic cardiomyopathy.     

Cellular and molecular aspects of familial hypertrophic cardiomyopathy caused by mutations in the cardiac troponin I gene

Mutations in the cardiac troponin I (CTnI) gene occur in approximately 5% of families with familial hypertrophic cardiomyopathy (FHC) and 20 mutations in this gene that cause FHC have now been described. The clinical manifestations of CTnI mutations that cause FHC are diverse, ranging from asymptomatic with high life expectancy to severe heart failure and sudden cardiac death. Most of these FHC mutations in CTnI result in cardiac hypertrophy unlike cardiac troponin T FHC mutations. All CTnI FHC mutations investigated in vitro affect the physiological function of CTnI, but other factors such as environmental or genetic factors (other genes that may affect the CTnI gene) are likely to be involved in influencing the severity of the phenotype produced by these mutations, since the distribution of hypertrophy among affected individuals varies within and between families. CTnI mutations mainly alter myocardial performance via changes in the Ca2+ -sensitivity of force development and in some cases alter the muscle relaxation kinetics due to haemodynamic or physical obstructions of blood flow from the left ventricle.     

Cellular and molecular aspects of familial hypertrophic cardiomyopathy caused by mutations in the cardiac troponin I gene

Mutations in the cardiac troponin I (CTnI) gene occur in 5% of families with familial hypertrophic cardiomyopathy (FHC) and 20 mutations in this gene that cause FHC have now been described. The clinical manifestations of CTnI mutations that cause FHC are diverse, ranging from asymptomatic with high life expectancy to severe heart failure and sudden cardiac death. Most of these FHC mutations in CTnI result in cardiac hypertrophy unlike cardiac troponin T FHC mutations. All CTnI FHC mutations investigated in vitro affect the physiological function of CTnI, but other factors such as environmental or genetic factors (other genes that may affect the CTnI gene) are likely to be involved in influencing the severity of the phenotype produced by these mutations, since the distribution of hypertrophy among affected individuals varies within and between families. CTnI mutations mainly alter myocardial performance via changes in the Ca²⁺-sensitivity of force development and in some cases alter the muscle relaxation kinetics due to haemodynamic or physical obstructions of blood flow from the left ventricle. (Mol Cell Biochem 263: 99–114, 2004)     

Linkage analysis of autosomal dominant atrio ventricular canal defects: exclusion of chromosome 21

The association between trisomy 21 and a high incidence of atrioventricular canal defects (AVCDs) indicates that a locus on chromosome 21 is involved in this congenital heart defect. We have investigated whether a genetic locus on chromosome 21 is also involved in familial nonsyndromic AVCDs. Short tandem repeat polymorphisms (STRPs) from chromosome 21 were used for linkage analysis of a family having multiple members affected with AVCDs. In this family, the gene for AVCDs is transmitted as an autosomal dominant with incomplete penetrance. The affected family members are nonsyndromic and have normal karyotypes. Two-point and multipoint linkage analyses produced significantly negative LOD scores for all informative markers. A comparison of the overlapping exclusion distances obtained for each marker at LOD equal -2.0 with the 1000:1 consensus genetic map of the markers, excludes chromosome 21 as the genetic location for AVCDs in this family. The exclusion of chromosome 21 indicates that another gene, not located on chromosome 21, is involved in atrioventricular canal defect formation.     

A molecular basis for familial hypertrophic cardiomyopathy: an alpha/beta cardiac myosin heavy chain hybrid gene

An alpha/beta cardiac myosin heavy chain (MHC) hybrid gene is coinherited with familial hypertrophic cardiomyopathy (FHC) in one kindred. FHC is a disease of the heart muscle characterized by a thickening of the left ventricular wall with myocyte and myofibrillar disarray that is inherited as an autosomal dominant trait. We demonstrate here and in the accompanying article that the cardiac MHC genes, which encode integral myofibrillar components, are mutated in all affected individuals from two unrelated families with FHC. In one kindred, an unequal crossover event during meiosis may have produced the alpha/beta cardiac MHC hybrid gene that is present in affected individuals. We conclude that mutations in the cardiac MHC genes can cause FHC.     

A family segregating a Friedreich ataxia phenotype that is not linked to the FRDA locus

Friedreich ataxia is an autosomal recessive neurodegenerative disorder. The genetic homogeneity to the FRDA locus on chromosome 9q13-21.1 has been observed in families from different ancestries. We report a Spanish family with two affected and three unaffected children. The segregated classical Friedreich ataxia did not show the expected linkage. The analysis focusses on flanking markers FR1, FR2, FR7 and FR5, excluding linkage 1 cM around the FRDA locus. The unique clinical hallmark in this family was the absence of cardiomyopathy after a long-term follow-up in the two affected children. In both patients serum vitamin E levels were normal. The present observations support the existence of a second locus in Friedreich ataxia, and we suggest that this form could be clinically characterized by the absence of muscular heart disease.     

A myomesin mutation associated with hypertrophic cardiomyopathy deteriorates dimerisation properties

Myomesin plays an important structural and functional role in the M-band of striated muscles. The C-terminal domain 13 of myomesin dimerises and forms antiparallel strands which cross-link neighboring Myosin filaments and titin in the M-line of the sarcomeres. These interactions stabilise the contractile apparatus during striated muscle contraction. Since myomesin is an important component of the M-band we screened the myomesin gene for genetic variants in patients with hypertrophic cardiomyopathy (HCM).We identified the missense mutation V1490I in domain 12 of myomesin in a family with inherited HCM. Analytical ultracentrifugation experiments, circular dichroism spectra, and surface plasmon resonance spectroscopy of myomesin fragments were carried out to investigate the effects of the mutation V1490I on structure and function of myomesin domains 11–13 and 12–13. Both the wild type and mutated myomesin domains My11–13 revealed similar secondary structures and formed stable dimers. Mutated myomesin domains My11–13 and My12–13 dimers revealed a reduced thermal stability and a significantly decreased dimerisation affinity, showing disturbed functional properties of V1490I mutated myomesin. However, monomeric myomesin domains My11–12, i.e. without dimerisation domain 13 showed no difference in thermal stability between wild type and V1490I mutated myomesin.In conclusion, the V1490I mutation associated with HCM lead to myomesin proteins with abnormal functional properties which affect dimerisation properties of myomesin domain 13. These effects may contribute to the pathogenesis of HCM.     

Rescue of tropomyosin-induced familial hypertrophic cardiomyopathy mice by transgenesis

Familial hypertrophic cardiomyopathy (FHC) is a disease caused by mutations in contractile proteins of the sarcomere. Our laboratory developed a mouse model of FHC with a mutation in the thin filament protein alpha-tropomyosin (TM) at amino acid 180 (Glu180Gly). The hearts of these mice exhibit dramatic systolic and diastolic dysfunction, and their myofilaments demonstrate increased calcium sensitivity. The mice also develop severe cardiac hypertrophy, with death ensuing by 6 mo. In an attempt to normalize calcium sensitivity in the cardiomyofilaments of the hypertrophic mice, we generated a chimeric alpha-/beta-TM protein that decreases calcium sensitivity in transgenic mouse cardiac myofilaments. By mating mice from these two models together, we tested the hypothesis that an attenuation of myofilament calcium sensitivity would modulate the severe physiological and pathological consequences of the FHC mutation. These double-transgenic mice "rescue" the hypertrophic phenotype by exhibiting a normal morphology with no pathological abnormalities. Physiological analyses of these rescued mice show improved cardiac function and normal myofilament calcium sensitivity. These results demonstrate that alterations in calcium response by modification of contractile proteins can prevent the pathological and physiological effects of this disease.     

No evidence for linkage of long QT syndrome and chromosome 11p15.5 markers in a Chinese family: evidence for genetic heterogeneity

Recently the defective gene locus in seven Caucasian families with the Romano-Ward form of long QT syndrome (LQT) has been mapped to chromosome 11p. To understand the molecular basis of LQT in Chinese, a three-generation family was investigated. Fourteen family members were studied and five individuals were diagnosed to be affected, according to electrocardiographic criteria. Two genomic DNA probes (c-Ha-ras-3-HVR and insulin-5-HVR) and one tetranucleotide repeat polymorphism (THZ) derived from chromosome 11p15.5 loci and previously demonstrated to be closely linked to LQT were used as probes to analyze this family. A lod score of less than -2 was noted for all three polymorphisms. Our data show that there was no evidence of linkage between these three loci and the gene for LQT in this studied family. We believe that this result provides additional evidence for genetic heterogeneity of LQT.     

Gender and aging in a transgenic mouse model of hypertrophic cardiomyopathy

Mutations in the cardiac myosin heavy chain (MHC) can cause familial hypertrophic cardiomyopathy (FHC). A transgenic mouse model has been developed in which a missense (R403Q) allele and an actin-binding deletion in the alpha-MHC are expressed in the heart. We used an isovolumic left heart preparation to study the contractile characteristics of hearts from transgenic (TG) mice and their wild-type (WT) littermates. Both male and female TG mice developed left ventricular (LV) hypertrophy at 4 mo of age. LV hypertrophy was accompanied by LV diastolic dysfunction, but LV systolic function was normal and supranormal in the young TG females and males, respectively. At 10 mo of age, the females continued to present with LV concentric hypertrophy, whereas the males began to display LV dilation. In female TG mice at 10 mo of age, impaired LV diastolic function persisted without evidence of systolic dysfunction. In contrast, in 10-mo-old male TG mice, LV diastolic function worsened and systolic performance was impaired. Diminished coronary flow was observed in both 10-mo-old TG groups. These types of changes may contribute to the functional decompensation typically seen in hypertrophic cardiomyopathy. Collectively, these results further underscore the potential utility of this transgenic mouse model in elucidating pathogenesis of FHC.     

Percutaneous septal ablation for left mid-ventricular obstructive hypertrophic cardiomyopathy: a case report

Background

Mid-ventricular obstructive hypertrophic cardiomyopathy (MVOHC) is a rare type of cardiomyopathy. The diagnosis is based on the hourglass appearance on the left ventriculogram and the presence of pressure gradient between apical and basal chamber of the ventriculum on the hemodynamic assessment.

Case presentation

The present case represents successful percutaneous treatment with septal ablation to patient with MVOHC associated with systolic anterior motion of the mitral valve and obstruction at both the mid-ventricular and outflow levels.

Conclusion

Alcohol septal ablation has been proposed as less invasive alternatives to surgery in patients with MVOHC.     

MYBPC3 polymorphism is a modifier for expression of cardiac hypertrophy in patients with hypertrophic cardiomyopathy

Clinical phenotype of hypertrophic cardiomyopathy exhibits significant inter- and intra-familial heterogeneities. To test if MYBPC3 polymorphism could modify the expression of cardiac hypertrophy, 226 patients with hypertrophic cardiomyopathy and 226 age- and sex-matched controls were recruited according to the diagnostic criteria of WHO. Genotyping was completed by using PCR, restrictive enzyme digestion, and sequencing. Three polymorphisms of MYBPC3 were studied, only the GG genotype at 18443 in exon 30 associated with thicker left ventricular wall (25.2+/-5.9 mm) in patient group, not the AA and AG genotypes (19.0+/-5.0mm, P<0.001). After multiple regression analysis for adjustment of age and sex, the association remained. No difference was found in the genotype distribution between control and patients. Our results point out that GG genotype of MYBPC3 might be a genetic risk factor for the expression of cardiac hypertrophic phenotype in the patients with hypertrophic cardiomyopathy.     

Myosin regulatory light chain mutation found in hypertrophic cardiomyopathy patients increases isometric force production in transgenic mice

FHC (familial hypertrophic cardiomyopathy) is a heritable form of cardiac hypertrophy caused by mutations in genes encoding sarcomeric proteins. The present study focuses on the A13T mutation in the human ventricular myosin RLC (regulatory light chain) that is associated with a rare FHC variant defined by mid-ventricular obstruction and septal hypertrophy. We generated heart-specific Tg (transgenic) mice with ~10% of human A13T-RLC mutant replacing the endogenous mouse cardiac RLC. Histopathological examinations of longitudinal heart sections from Tg-A13T mice showed enlarged interventricular septa and profound fibrotic lesions compared with Tg-WT (wild-type), expressing the human ventricular RLC, or non-Tg mice. Functional studies revealed an abnormal A13T mutation-induced increase in isometric force production, no change in the force-pCa relationship and a decreased Vmax of the acto-myosin ATPase. In addition, a fluorescence-based assay showed a 3-fold lower binding affinity of the recombinant A13T mutant for the RLC-depleted porcine myosin compared with WT-RLC. These results suggest that the A13T mutation triggers a hypertrophic response through changes in cardiac sarcomere organization and myosin cross-bridge function leading to abnormal remodelling of the heart. The significant functional changes observed, despite a low level of A13T mutant incorporation into myofilaments, suggest a 'poison-peptide' mechanism of disease.     

Evidence for linkage of human primary systemic carnitine deficiency with D5S436: a novel gene locus on chromosome 5q.

Primary systemic carnitine deficiency (SCD) is a rare hereditary disorder transmitted by an autosomal recessive mode of inheritance. The disorder includes cardiomyopathy, muscle weakness, hypoketotic coma with hypoglycemia, and hyperammonemia. In this study, we conducted a linkage analysis of a Japanese SCD family with a proband-a 9-year-old girl-and 26 members. The serum and urinary carnitine levels were determined for all members. The entire genome was searched for linkage to the gene locus for SCD, by use of a total of approximately 300 polymorphic markers located approximately 15-20 cM apart. In the family, there were two significantly different phenotypes, in terms of serum free-carnitine levels: low serum free-carnitine level (29.5+/-5.0 microM; n=14) and normal serum free-carnitine level (46.8+/-6.2 microM; n=12). There was no correlation of urinary free-carnitine levels with the low serum-level phenotype (putative heterozygote), but in normal phenotypes (wild type) urinary levels decreased as the serum levels decreased; renal resorption of free carnitine appeared to be complete in wild-type individuals, when the serum free-carnitine level was <36 microM. Linkage analysis using an autosomal dominant mode of inheritance of heterozygosity revealed a tight linkage between the disease allele and D5S436 on chromosome 5q, with a two-point LOD score of 4.98 and a multipoint LOD score of 5.52. The haplotype analysis revealed that the responsible genetic locus lies between D5S658 and D5S434, which we named the "SCD" locus. This region was syntenic with the jvs locus, which is responsible for murine SCD. Phylogenic conversion of the SCD locus strongly suggests involvement of a single gene, in human SCD.     

Mapping eight new polymorphisms in 11q13 in the vicinity of multiple endocrine neoplasia type 1: identification of a new distal recombinant

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder that predisposes affected individuals to neoplasms of the parathyroid glands, endocrine pancreas, anterior pituitary, and carcinoids. The MEN1 locus has been localized by family studies to 11q13, flanked by markers PGA and D11S97. Eight new polymorphisms located in three separate radiation-reduced somatic cell hybrid segregation groups were developed. The order of the new markers, within the context of previously described loci, was determined by linkage analysis on the Venezuelan reference pedigree. Four independent MEN1 families, consisting of 57 affected individuals, and 70 individuals at-risk for the disease were genotyped. Sixteen people inherited a chromosome that shows recombination between a linked marker and the disease. The nearest proximal and distal markers that show recombination with the disease are D11S822 and GSTP1, respectively, thereby narrowing the candidate region for MEN1 by 50% on the distal side. Using these loci in haplotype analysis, an accurate presymptomatic molecular diagnostic test has been developed. These new markers in 11q13 linked to MEN1 also facilitate the genetic and physical characterization of this very gene-rich region.     

Genetic mapping of ossification of the posterior longitudinal ligament of the spine.

Ossification of the posterior longitudinal ligament of the spine (OPLL) is recognized as a common disorder among Japanese and throughout Asia. Estimates of its prevalence are in the range of 1. 9%-4.3%. Although its etiology is thought to involve a multiplicity of factors, epidemiological and family studies strongly implicate genetic susceptibility in the pathogenesis of OPLL. In this study we report an identification of a predisposing locus for OPLL, on chromosome 6p, close to the HLA complex. The evidence for this localization is provided by a genetic-linkage study of 91 affected sib pairs from 53 Japanese families. In this sib-pair study, D6S276, a marker lying close to the HLA complex, gives evidence for strongly significant linkage (P = .000006) to the OPLL locus. A candidate gene in the region, that for collagen 11A2, was analyzed for the presence of molecular variants in affected probands. Of 19 distinct variants identified, 4 showed strong statistical associations with OPLL (highest P = .0004). These observations of linkage and association, taken together, show that a genetic locus for OPLL lies close to the HLA region, on chromosome 6p.