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The ubiquitin-proteasome system is responsible for the disappearance of truncated cardiac myosin-binding protein C, and the suppression of its activity contributes to cardiac dysfunction. This study investigated whether missense cardiac myosin-binding protein C gene (MYBPC3) mutation in hypertrophic cardiomyopathy (HCM) leads to destabilization of its protein, causes UPS impairment, and is associated with cardiac dysfunction. Mutations were identified in Japanese HCM patients using denaturing HPLC and sequencing. Heterologous expression was investigated in COS-7 cells as well as neonatal rat cardiac myocytes to examine protein stability and proteasome activity. The cardiac function was measured using echocardiography. Five novel MYBPC3 mutations -- E344K, DeltaK814, Delta2864-2865GC, Q998E, and T1046M -- were identified in this study. Compared with the wild type and other mutations, the E334K protein level was significantly lower, it was degraded faster, it had a higher level of polyubiquination, and increased in cells pretreated with the proteasome inhibitor MG132 (50 microM, 6 h). The electrical charge of its amino acid at position 334 influenced its stability, but E334K did not affect its phosphorylation. The E334K protein reduced cellular 20 S proteasome activity, increased the proapoptotic/antiapoptotic protein ratio, and enhanced apoptosis in transfected Cos-7 cells and neonatal rat cardiac myocytes. Patients carrying the E334K mutation presented significant left ventricular dysfunction and dilation. The conclusion is the missense MYBPC3 mutation E334K destabilizes its protein through UPS and may contribute to cardiac dysfunction in HCM through impairment of the ubiquitin-proteasome system. Show less

To reveal genotype-phenotype correlation of disease-causing gene mutations in Chinese hypertrophic cardiomyopathy (HCM) pedigree. Peripheral venous blood samples were collected from two Chinese HCM families and 120 healthy subjects were recruited as normal control. The full encoding exons and flanking sequences of the cardiac troponin T gene (TNNT2), beta-myosin heavy chain gene (MYH7) and myosin binding protein C gene (MYBPC3) were amplified with the polymerase chain reaction method, DNA sequencing was used to detect the mutation. In ZZJ family, mutation G12101A was identified in exon 21 of MYBPC3 gene in 4 family members [the arginine (R) converted to histidine (H)]. In this pedigree, three out of eight family members were diagnosed as HCM and with a penetrance of 75%. In FHL family, mutation G15391A was identified in exon 23 of MYH7 gene in 3 family members [the glutamic acid (E) converted to lysine (K)]. In this pedigree, three out of six family members were diagnosed as HCM and with a penetrance of 100%. Echocardiography showed obstruction of left ventricular outflow tract in two out of the three HCM patients. Our results showed that the G12101A mutation of MYBPC3 gene is the causal mutation of familial HCM with mild phenotype. The G15391A mutation of MYH7 gene is the causal mutation of familial HCM with malignant phenotype and a penetrance of 100%. Screening mutations in the MYH7 gene should be viewed as a reasonable procedure in obstructive HCM patients. Show less

Mutations in MYBPC3 encoding myosin binding protein C belong to the most frequent causes of hypertrophic cardiomyopathy (HCM) and may also lead to dilated cardiomyopathy (DCM). MYBPC3 mutations initially were considered to cause a benign form of HCM. The aim of this study was to examine the clinical outcome of patients and their relatives with 18 different MYBPC3 mutations. 87 patients with HCM and 71 patients with DCM were screened for MYBPC3 mutations by denaturing gradient gel electrophoresis and sequencing. Close relatives of mutation carriers were genotyped for the respective mutation. Relatives with mutation were then evaluated by echocardiography and magnetic resonance imaging. A detailed family history regarding adverse clinical events was recorded. In 16 HCM (18.4%) and two DCM (2.8%) index patients a mutation was detected. Seven mutations were novel. Mutation carriers exhibited no additional mutations in genes MYH7, TNNT2, TNNI3, ACTC and TPM1. Including relatives of twelve families, a total number of 42 mutation carriers was identified of which eleven (26.2%) had at least one adverse event. Considering the twelve families and six single patients with mutations, 45 individuals with cardiomyopathy and nine with borderline phenotype were identified. Among the 45 patients, 23 (51.1%) suffered from an adverse event. In eleven patients of seven families an unexplained sudden death was reported at the age between 13 and 67 years. Stroke or a transient ischemic attack occurred in six patients of five families. At least one adverse event occurred in eleven of twelve families. MYBPC3 mutations can be associated with cardiac events such as progressive heart failure, stroke and sudden death even at younger age. Therefore, patients with MYBPC3 mutations require thorough clinical risk assessment. Show less

1. Familial hypertrophic cardiomyopathy (FHC) is a primary cardiac disorder characterized by myocardial hypertrophy that demonstrates substantial diversity in both genetic causes and clinical manifestations. 2. Clinical heterogeneity can be explained by the causative gene (at least 13 have been identified to date), the position of the amino acid residue affected by a mutation within the protein (over 450 mutations have been reported to date) and modifying genetic and environmental factors. 3. Multiple mutations are found in up to 5% of human FHC cases, who typically present with a more severe phenotype compared with single-mutation carriers (i.e. earlier onset of disease, greater left ventricular hypertrophy and a higher incidence of sudden cardiac death events). 4. Multiple mutations usually involve MYH7, MYBPC3 and, to a lesser extent, TNNI2, reflecting the higher contribution of mutations in these genes to FHC. 5. Multiple-mutation mouse models appear to mimic the human multiple-mutation phenotype and, thus, will help improve our understanding of disease pathogenesis. The models provide a tool for future studies of disease mechanisms and signalling pathways in FHC and its sequelae (i.e. heart failure and sudden death), thereby allowing identification of novel targets for potential therapies and disease prevention strategies. Show less

Phosphorylation of myosin binding protein C (MyBP-C) was investigated in intraventricular septum samples taken from patients with hypertrophic cardiomyopathy undergoing surgical septal myectomy. These samples were compared with donor heart muscle, as a well-characterised control tissue, and with end-stage failing heart muscle. MyBP-C was partly purified from myofibrils using a modification of the phosphate-EDTA extraction of Hartzell and Glass. MyBP-C was separated by SDS-PAGE and stained for phosphoproteins using Pro-Q Diamond followed by total protein staining using Coomassie Blue. Relative phosphorylation level was determined from the ratio of Pro-Q Diamond to Coomassie Blue staining of MyBP-C bands as measured by densitometry. We compared 9 myectomy samples and 9 failing heart samples with 9 donor samples. MyBP-C phosphorylation in pathological muscle was lower than in donor (myectomy 40+/-2% of donor, P<0.0001; failing 45+/-3% of donor, P<0.0001). 6 myectomy samples were identified with MYBPC3 mutations, one with MYH7 mutation and two remained unknown, but there was no correlation between MYBPC3 mutation and MyBP-C phosphorylation level. In order to determine the number of phosphorylated sites in human cardiac MyBP-C samples, we phosphorylated the recombinant MyBP-C fragment, C0-C2 (1-453) with PKA using (gamma32)P-ATP up to 3.5 mol Pi/mol C0-C2. This measurement of phosphorylation was used to calibrate measurements of phosphorylation in SDS-PAGE using Pro-Q Diamond stain. The level of phosphorylation in donor heart MyBP-C was calculated to be 4.6+/-0.6 mol Pi/mol and 2.0+/-0.3 mol Pi/mol in myectomy samples. We conclude that MyBP-C is a highly phosphorylated protein in vivo and that diminished MyBP-C phosphorylation is a feature of both end-stage heart failure and hypertrophic cardiomyopathy. Show less

An autosomal dominant mutation has been identified in the myosin-binding protein C (MYBPC3) gene of Maine Coon cats. This mutation changes a conserved amino acid and computationally alters the protein conformation of this gene in Maine Coon cats with hypertrophic cardiomyopathy. The prevalence of this mutation is unknown. To determine the genetic prevalence of the MYBPC3 mutation in a large cohort of predominantly Maine Coon cats. Three thousand three hundred and ten DNA samples (blood or buccal swab) from cats. This retrospective study reviewed the Veterinary Cardiac Genetics Laboratory database at Washington State University for samples submitted for evaluation of the Maine Coon MYBPC3 mutation. The data were analyzed with respect to the breed of cat, mutation status (negative, heterozygous, homozygous), and geographic origin of the submission. In the population of cats studied, Maine Coon cats accounted for 100% of all cats positive for the mutation, and the worldwide percentage of Maine Coon cats carrying the MYBPC3 mutation was 34%. The prevalence of the mutation (heterozygous or homozygous) was very similar among countries of submission, suggesting that the 34% mutation rate of the tested samples is a reasonable estimate of the true prevalence of the mutation within the breed. Because of the high prevalence of this mutation, a breeding recommendation to eliminate all cats with the mutation could have a substantial impact on the gene pool. Additional studies are indicated to explore the relationship between genotype and clinical outcome in affected cats. Show less

Hypertrophic cardiomyopathy (HCM) is a genetic disease associated with mutations in genes encoding cardiac sarcomere proteins. A mutation is identified in two-thirds of cases, and more frequently in familial forms. Doubts remain concerning the true identity of the sporadic form. To compare, in a genotyped population, the phenotypic expression of the disease over time in patients with familial and sporadic HCM. 79 patients with HCM, aged 39 +/- 17.8 years at diagnosis, were followed for 12 +/- 9.5 (1-30) years and divided into two groups: G1 (familial)--68 patients (24 unrelated index patients, 44 relatives), follow-up time (FUP) 12 +/- 9.8 (1-30) years; G2 (sporadic)1 index patients (no phenotypic disease in first-degree relatives), FUP 10.8 +/- 8 (2-24) years. Fabry disease was excluded in G2. The two groups were compared regarding clinical, ECG and echocardiographic (echo) features at diagnosis and after FUP. Five sarcomere genes (MYH7, MYBPC3, TNNT2, MYL2 and TNNI3) were screened for mutations by direct sequencing, after PCR amplification with intronic sets of oligonucleotide primers designed according to the published genomic sequence of the genes. A) Thirteen different mutations (in 3 genes) were identified in 14 index patients in G1; only in one patient in G2 was a mutation found. B) The two groups differed clinically in age at diagnosis (G1: 37.18 (4-79) years; G2: 51 +/- 14 (19-67) years; p = 0.02), and family history of sudden cardiac death (G1: 12/24 families; G2: 1/11 families; p = 0.04). Age, gender, FUP, symptoms, need for medical treatment, cardiovascular (CV) hospitalization and mortality (CV or any cause) were similar. C) ECG patterns did not differ, although significant (but similar) changes occurred in 45% (G1) and 36% (G2) of patients (p = 0.75). These changes were in the same direction, with a trend in both groups toward the development of atrial fibrillation and/or advanced conduction disease. D) Echo features (only considered in adults) were similar despite significant changes during FUP (in 68% of G1, and 82% of G2; p = 0.48). These changes also followed the same tendency: progression to a more diffuse pattern of ventricular hypertrophy (G1: 52%; G2: 73%; p = 0.33) and development of left atrial dilatation (G1: 37%; G2: 45%; p = 0.52). The similar phenotypic expression and behavior over time in familial and sporadic forms of HCM strongly indicate that the disease is one and the same. Differences in genetic findings, age at diagnosis and family history of sudden death suggest that sporadic forms may be caused by low penetrance de novo mutations in sarcomeric genes other than those associated with familial disease. Show less

Familial hypertrophic cardiomyopathy (HCM) is a leading cause of sudden cardiac death among young and apparently healthy people. Autosomal dominant mutations within genes encoding sarcomeric proteins have been identified. An autosomal recessive form of HCM has been discovered in a group of Amish children that is associated with poor prognosis and death within the first year of life. Affected patients experienced progressive cardiac failure despite maximal medical treatment. Postmortem histology showed myofibre disarray and myocyte loss consistent with refractory clinical deterioration in affected infants. To conduct a genome-wide screen for linkage and try to identify an autozygous region which cosegregates with the infant cardiac phenotype An autozygous region of chromosome 11 which cosegregates with the infant cardiac phenotype was identified. This region contained the MYBPC3 gene, which has previously been associated with autosomal dominant adult-onset HCM. Sequence analysis of the MYBPC3 gene identified a splice site mutation in intron 30 which was homozygous in all affected infants. All surviving patients with the homozygous MYBPC3 gene mutations (3330+2T>G) underwent an orthotopic heart transplantation. Homozygous mutations in the MYBPC3 gene have been identified as the cause of severe infantile HCM among the Amish population. Show less

Hypertrophic cardiomyopathy (HCM) is a heterogeneous autosomal dominant cardiac disorder with a prevalence of 1 in 500. Over 450 different pathogenic mutations in at least 16 genes have been identified so far. The large allelic and genetic heterogeneity of HCM requires high-throughput, rapid, and affordable mutation detection technologies to efficiently integrate molecular screening into clinical practice. We developed a custom DNA resequencing array that contains both strands of all coding exons (160), splice-site junctions, and 5'UTR regions of 12 genes that have been clearly implicated in HCM (MYH7, MYBPC3, TNNT2, TPM1, TNNI3, MYL3, MYL2, CSRP3, PLN, ACTC, TNNC1, and PRKAG2). We analyzed a first series of 38 unrelated patients with HCM (17 familial, 21 sporadic). A total of 953,306 bp across the 38 patients were sequenced with a mean nucleotide call rate of 96.92% (range: 93-99.9%). Pathogenic mutations (single nucleotide substitutions) in MYH7, MYBPC3, TNNI3, and MYL3 (six known and six novel) were identified in 60% (10/17) of familial HCM and 10% of sporadic cases (2/21). The high-throughput HCM resequencing array is the most rapid and cost-effective tool for molecular testing of HCM to date; it thus has considerable potential in diagnostic and predictive testing, and prognostic stratification. Show less

The childhood onset of idiopathic cardiac hypertrophy that occurs without a family history of cardiomyopathy can portend a poor prognosis. Despite morphologic similarities to genetic cardiomyopathies of adulthood, the contribution of genetics to childhood-onset hypertrophy is unknown. We assessed the family and medical histories of 84 children (63 boys and 21 girls) with idiopathic cardiac hypertrophy diagnosed before 15 years of age (mean [+/-SD] age, 6.99+/-6.12 years). We sequenced eight genes: MYH7, MYBPC3, TNNT2, TNNI3, TPM1, MYL3, MYL2, and ACTC. These genes encode sarcomere proteins that, when mutated, cause adult-onset cardiomyopathies. We also sequenced PRKAG2 and LAMP2, which encode metabolic proteins; mutations in these genes can cause early-onset ventricular hypertrophy. We identified mutations in 25 of 51 affected children without family histories of cardiomyopathy and in 21 of 33 affected children with familial cardiomyopathy. Among 11 of the 25 children with presumed sporadic disease, 4 carried new mutations and 7 inherited the mutations. Mutations occurred predominantly (in >75% of the children) in MYH7 and MYBPC3; significantly more MYBPC3 missense mutations were detected than occur in adult-onset cardiomyopathy (P<0.005). Neither hypertrophic severity nor contractile function correlated with familial or genetic status. Cardiac transplantation and sudden death were more prevalent among mutation-positive than among mutation-negative children; implantable cardioverter-defibrillators were more frequent (P=0.007) in children with family histories that were positive for the mutation. Genetic causes account for about half of presumed sporadic cases and nearly two thirds of familial cases of childhood-onset hypertrophy. Childhood-onset hypertrophy should prompt genetic analyses and family evaluations. Show less

No data are available on survival analysis and longitudinal evolution of patients with gene mutations of beta-myosin heavy chain (MYH7) and myosin binding protein C (MYBPC3) in Chinese. To prospectively investigate whether different gene mutations confer distinct prognosis. We performed a prospective study in 70 HCM patients and 46 genetically affected family members without HCM-phenotype with direct DNA sequencing of MYH7 and MYBPC3, clinical assessments, and 5.8 +/- 1.8 years follow-up. After follow-up, more surgical intervention (8/52 versus 0/18, p < 0.001), higher sudden death risk (7/52 versus 0/18, p < 0.001) and shorter life span were found in patients with MYH7 mutations than in patients with MYBPC3 mutations (45.1 +/- 14.0 versus 73.5 +/- 7.5 years, p = 0.03). Seven of the 27 mutation carriers of MYH7 had clinical presentations of HCM, but no carriers of MYBPC3 mutations developed to HCM during follow-up. Maximal wall thickness was thicker in the patients carrying mutations in the global region of MYH7 than in those carrying mutations in the rod region of MYH7 (21.5 +/- 6.6 versus 15 +/- 6.1 mm, p < 0.05) at baseline. More sudden death (7/41 versus 0/11) and left ventricular dysfunction (NYHA Class III approximately IV, 17/32 versus 1/10) were identified in patients with mutations in the global region of MYH7 than in patients with other mutations. MYH7 mutations, especially in the global region, cause malignant clinical phenotypes. Show less

Hypertrophic cardiomyopathy is primarily caused by mutations in genes encoding cardiac sarcomere proteins. Large screening studies identify mutations in 35-65% of the diagnosed patients and 15-30% of these are discovered within the MYBPC3 gene encoding the cardiac myosin binding protein C. The aim of this study is to determine whether intronic variation flanking the three micro-exons in MYBPC3 is disease-causing. Two hundred and fifty unrelated patients with hypertrophic cardiomyopathy were genotyped in MYBPC3, using automated single-strand conformation polymorphism, and sequenced for confirmation. Mutations located in the flanking introns of the MYBPC3 micro-exons were examined using in silico methods. Ectopic expression of mRNA in blood leukocytes in the respective patients was examined using reverse transcription-PCR. A total of seven mutations were discovered in the introns flanking the two micro-exons 10 and 14, but none were found in introns flanking exon 11. Functional studies together with co-segregation analysis indicate that four mutations are associated with HCM, in the respective patients. All four mutations result in premature termination codons, which suggests that haploinsufficiency is a pathogenic mechanism of this type of mutation. It is demonstrated that the use of in silico methods together with RNA studies on peripheral blood leukocytes is a useful tool to evaluate the potential effects of mutations on pre-mRNA splicing. Show less

Mutations in the gene of myosin binding protein C (MYBPC3) are currently considered the most frequent cause of hypertrophic cardiomyopathy (HCM). To assess the frequency of selected mutations in MYBPC3 in the Polish population of HCM patients. One hundred eighteen patients with HCM and 118 healthy, age and sex-matched controls were screened for the presence of 14 mutations of MYBPC3 using real time polymerase chain reaction. Five different mutations were found in six patients in the HCM group whereas no mutations were present in the control group. In three cases the mutations were missense (Arg502Gln, Cys566Arg, Asn755Lys) and in three cases terminal (Gln425ter, Gln1061ter in two unrelated probands). Mutations in MYBPC3 should be considered a frequent cause of HCM in Poland. Show less

Hypertrophic cardiomyopathy (HCM) is a complex cardiac muscular disorder, inherited as an autosomal dominant disease with variable penetrance. Cardiac myosin-binding protein C (MyBPC) is the predominant myosin-binding protein isoform in the heart muscle. One hundred forty-seven mutations have been detected in MYBPC3, accounting for 15% of all HCM cases. To screen exons 16, 18, 19, 22, 24, 28, 30, 31 and 34 in the MYBPC3 gene in Indian HCM patients. Sixty control and 95 HCM samples were collected from cardiology units of the CARE Hospital (Nampally, Banjara Hills, Secunderabad, India) for genomic DNA isolation followed by polymerase chain reaction and single-stranded conformational polymorphism analysis. Screening of the exons revealed two variations - one novel frame shift mutation in exon 19 at the nucleotide position 11577-11578 and one novel single nucleotide polymorphism (SNP) in codon 1093 of exon 31, coding for glycine with a C>T transition (GGC/GGT), in addition to the seven known SNPs mainly in the intronic region and one known missense mutation D770N in this population. The novel frame shift mutation identified in exon 19, D570fs, with the insertion of an adenine residue in codon 570 coding for aspartate, results in a premature termination codon that produces a truncated protein lacking myosin- and titin-binding sites, explaining the role of the nonsense-mediated decay pathway. A novel SNP identified in codon 1093 of exon 31 was found to be a synonymous codon, which may have a regulatory effect at the translational level, attributing to affinity differences between codon-anticodon interactions. The screening of this gene may be relevant in the Indian context. Show less

Dissecting the complex genetic basis of hypertrophic cardiomyopathy (HCM) may be key to both better understanding and optimally managing this most prevalent genetic cardiovascular disease. An array-based resequencing (ABR) assay was developed to facilitate genetic testing in HCM. An Affymetrix resequencing array and a single long-range PCR protocol were developed to cover the 3 most commonly affected genes in HCM, MYH7 (myosin, heavy chain 7, cardiac muscle, beta), MYBPC3 (myosin binding protein C, cardiac), and TNNT2 [troponin T type 2 (cardiac)]. The assay detected the underlying point mutation in 23 of 24 reference samples and provided pointers toward identifying a G insertion and a 3-bp deletion. The comparability of array-based assay results to conventional capillary sequencing was > or =99.9%. Both techniques detected 1 heterozygous variant that was missed by the other method. The data provide evidence that ABR can substantially reduce the high workload previously associated with a genetic test for HCM. Therefore, the HCM array could facilitate large-scale studies aimed at broadening the understanding of the genetic and phenotypic diversity of HCM and related cardiomyopathies. Show less

Hypertrophic cardiomyopathy (HCM) is a disease of mutant sarcomeric proteins (except for phenocopy). Cardiac hypertrophy is the clinical diagnostic hallmark of HCM and a major determinant of morbidity and mortality in various cardiovascular diseases. However, there is remarkable variability in expression of hypertrophy, even among HCM patients with identical causal mutations. We hypothesized modifier genes are partly responsible for the variation in hypertrophic expressivity. To map the modifier loci, we typed 811 short-tandem repeat markers ( approximately 5 cMdense) in 100 members of an HCM family including 36 with the InsG791 mutation in MYBPC3. We performed oligogenic simultaneous segregation and linkage analyses using Markov Chain Monte Carlo methods and detected linkage on 3q26.2 (180 cM), 10p13 (41 cM), 17q24 (108 cM) with log of the posterior placement probability ratio (LOP) of 3.51, 4.86 and 4.17, respectively, and suggestive linkage (LOP of 2.40) on 16q12.2 (73 cM). The effect sizes varied according to the modifier locus, age and sex. It ranged from approximately 8 g shift in left ventricular mass for 10p13 locus heterozygosity for the common allele to approximately 90 g shift for 3q26.2 locus homozygosity for the uncommon allele. Refining the 10p13 locus restricted the candidate modifier genes to ITGA8, C10orf97 (CARP) and PTER. ITGA8 and CARP are biologically plausible candidates as they are implicated in cardiac fibrosis and apoptosis, respectively. Since cardiac hypertrophy is a major determinant of total and cardiovascular mortality and morbidity, regardless of the etiology, identification of the specific modifier genes could have significant prognostic and therapeutic implications for various cardiovascular diseases. Show less

Hypertrophic cardiomyopathy is an autosomal dominant inherited disease characterized by ventricular hypertrophy and myofibril disarray. Mutations responsible for hypertrophic cardiomyopathy have been identified in 11 genes that encode for cardiac sarcomere proteins. Traditionally, hypertrophic cardiomyopathy due to mutation of the myosin-binding protein C gene (MYBPC3) has been thought to follow a benign course. We report a family with several members affected by hypertrophic cardiomyopathy in which there was a high incidence of sudden death. Disease was presumably caused by the substitution of cytosine by guanine at nucleotide 269 of MYBPC3 mRNA. This mutation, which has not previously been described, modifies codon 79, which encodes for the incorporation of a tyrosine, and gives rise to a stop codon. The mutation described here appears to confer a higher risk than that previously associated with hypertrophic cardiomyopathy due to MYBPC3 gene mutation. Show less

Hypertrophic cardiomyopathy (HCM) is a genetic disorder caused by mutations in sarcomeric proteins (excluding phenocopy). The causal genes in approximately one-third of the cases remain unknown. We identified a family comprised of 6 clinically affected members. The phenotype was characterized by early onset of symptoms, pronounced cardiac hypertrophy, and cardiac arrhythmias. We excluded MYH7, MYBPC3, TNNT2, and ACTC1 as the causal gene either by direct sequencing or by haplotype analysis. To map the putative candidate sarcomeric gene, we perforbold locus-specific haplotyping to detect cosegregation of the locus haplotype with the phenotype, followed by mutation screening. We genotyped 5 short-tandem-repeat markers that spanned a 4.4-centimorgan region on 4q26-q27 locus and encompassed myozenin 2 (MYOZ2), a Z-disk protein. The maximum logarithm of odds score was 2.03 (P=0.005). All affected members shared a common haplotype, implicating MYOZ2 as the causal gene. To detect the causal mutation, we sequenced all exons and exon-intron boundaries of MYOZ2 in 10 family members and identified a T-->C missense mutation corresponding to S48P substitution, which cosegregated with inheritance of HCM (N=6). It was absent in 4 clinically normal family members and in 658 additional normal individuals. To determine frequency of the MYOZ2 mutations in HCM, we sequenced MYOZ2 in 516 HCM probands and detected another missense mutation (I246M). It was absent in 2 normal family members and 517 controls. Both mutations affect highly conserved amino acids. We conclude MYOZ2 is a novel causal gene for human HCM. Show less

The proximal chromosome 11p contiguous gene deletion syndrome (P11pDS), also known as Potocki-Shaffer syndrome (PSS) or DEFECT 11 (OMIM 601224), is a disorder associated with foramina parietalia permagna and multiple osteochondroma (exostoses). Additional features include mental retardation, craniofacial anomalies, seizures and genitourinary abnormalities. Here, clinico-pathological findings of a unique patient with all of these features and, additionally, enlarged ventricles, hypertrophic obstructive cardiomyopathy and adipositas are described. The brain showed malformative lesions with hallmarks of disturbed bulk growth including micrencephaly, periventricular nodular heterotopias and focal cortical dysplasia in the nodulus of the cerebellar vermis. In addition, symmetric foci with vacuolation of the underlying neuropil, intermingled macrophages and large bizarre, partially vacuolated, reactive astrocytes were found. The proximal short arm of chromosome 11 harbors several candidate genes that could explain the patient's signs and symptoms including ALX4 and EXT2, which are always present in the interstitial deletion of the short arm of chromosome 11 in PSS. In addition, MYBPC3 would be a good candidate for the hypertrophic cardiomyopathy. Furthermore, adipositas might be related to the MAPK8IP1 gene. To the best of our knowledge, the present patient is the oldest one so far described with PSS phenotype and the only case that has undergone detailed neuropathological investigation. Show less

To study the disease-causing gene mutation in Chinese patients with hypertrophic cardiomyopathy (HCM) and to analyze the genotype and phenotype correlation. One family (n = 27) affected with HCM were chosen for the study. The full encoding exons and flanking sequences of beta-myosin heavy chain gene (MYH7) and cardiac myosin-binding protein C gene (MYBPC3) were amplified with PCR and the products were sequenced. The clinical data including symptom, physical, echocardiography and electrocardiography examinations were collected. We identified a 13261 G > A mutation, which causes a missense mutation (G758D) in exon 23 of MYBPC3 in 9 family members. One mutation carrier suffered from dilated cardiomyopathy (DCM) with asymmetric interventricular septal hypertrophy (14 mm). Another mutation carrier was diagnosed as HCM. The 13261 G > A mutation is associated with a DCM-like HCM and HCM phenotype in this Chinese family affected with HCM. Show less

Noncompaction of the left ventricle is a descriptive anatomical term and recently recognized primary cardiomyopathy. Cardiac imaging now allows for prompt detection. The specific etiology remains poorly understood, however, and the major genetic determinants are unknown. This review describes recent data showing the genetic heterogeneity and overlap with other cardiomyopathies. Understanding the genetics may depend on clarifying the distinctive diagnostic features and investigating the contribution of all known cardiomyopathy-causing genes with overlapping morphology. Adding to the known genes (TAZ, DTNA, LDB3 and LMNA), recent work has identified SCN5A, MYH7 and MYBPC3 as associated loci. LDB3 may also be a genetic modifier. Case reports and linkage studies suggest additional loci at 1p36, 1q43 and 11p15. Aside from Barth syndrome, other genetic and metabolic syndromes with noncompaction have been described. Despite this, large studies have failed to identify the etiology in the majority of patients. Despite advances in detection, comprehensive clinical, pathological, genetic, and family studies are necessary to define the phenotypic overlap with other cardiomyopathies. Without a more precise understanding of its etiology, the answers to the questions regarding the clinical relevance and management of patients with noncompaction of the left ventricle will remain elusive. Show less

Long QT Syndrome, Marfan Syndrome, hypertrophic and dilated cardiomyopathy are caused by mutations in large, multi-exon genes that are principally expressed in cardiovascular tissues. Genetic testing for these disorders is labor-intensive and expensive. We sought to develop a more rapid, comprehensive, and cost-effective approach. Paired whole blood samples were collected into tubes with or without an RNA-preserving solution, and harvested for whole blood RNA or leukocyte DNA, respectively. Large overlapping cDNA fragments from KCNQ1 and KCNH2 (Long QT Syndrome), MYBPC3 (hypertrophic and dilated cardiomyopathy), or FBN1 (Marfan Syndrome) were amplified from RNA and directly sequenced. Variants were confirmed in leukocyte DNA. All 4 transcripts were amplified and sequenced from whole blood mRNA. Six known and 2 novel mutations were first identified from RNA of 10 probands, and later confirmed in genomic DNA, at considerable savings in time and cost. In one patient with MFS, RNA sequencing directly identified a splicing mutation. Results from RNA and DNA were concordant for single nucleotide polymorphisms at the same loci. Taking advantage of new whole blood RNA stabilization methods, we have designed a cost-effective, comprehensive method for mutation detection that should significantly facilitate clinical genetic testing in four lethal cardiovascular disorders. Show less

Familial hypertrophic cardiomyopathy (HCM) is a primary myocardial disease with a prevalence of 1 in 500 in human beings. Causative mutations have been identified in several sarcomeric genes, including the cardiac myosin binding protein C (MYBPC3) gene. Heritable HCM also exists in a large-animal model, the cat, and we have previously reported a mutation in the MYBPC3 gene in the Maine coon breed. We now report a separate mutation in the MYBPC3 gene in ragdoll cats with HCM. The mutation changes a conserved arginine to tryptophan and appears to alter the protein structure. The ragdoll is not related to the Maine coon and the mutation identified is in a domain different from that of the previously identified feline mutation. The identification of two separate mutations within this gene in unrelated breeds suggests that these mutations occurred independently rather than being passed on from a common founder. Show less

Hypertrophic cardiomyopathy is typically inherited in an autosomal dominant pattern and has a variable age of onset and prognosis. Mutations in the myosin-binding protein C (MYBPC3) gene are one of the most frequent genetic causes of the disease. Patients with MYBPC3 mutations generally have a late onset and a relatively good prognosis. We report here more than 20 Old Order Amish children with severe neonatal hypertrophic cardiomyopathy caused by a novel homozygous splice site mutation in the MYBPC3 gene. The affected children typically presented with signs and symptoms of congestive heart failure during the first 3 weeks of life. Echocardiography revealed hypertrophic non-obstructive cardiomyopathy. These children had a life span averaging 3-4 months. All patients died from heart failure before 1 year of age unless they received a heart transplant. A genome-wide mapping study was performed in three patients. The disease related gene was localized to a 4.6 Mb region on chromosome 11p11.2-p11.12. This homozygous block contained MYBPC3, a previously identified cardiomyopathy related gene. We identified a novel homozygous mutation, c.3330 + 2T > G, in the splice-donor site of MYBPC3 intron 30. The mutation resulted in skipping of the 140-bp exon 30, which led to a frame shift and premature stop codon in exon 31 (p.Asp1064GlyfsX38). We have found a substantial incidence of this phenotype in Old Order Amish communities. It is also concerning that many unidentified heterozygous individuals who are at risk for development of hypertrophic cardiomyopathy do not receive proper medical attention in the communities. Show less

To study the disease-causing gene mutation in Chinese patients with familial hypertrophic cardiomyopathy (FHC) and to analyze the correlation between the genotype and the phenotype. Peripheral blood samples were collected from 40 members from a family affected with FHC, and 120 healthy volunteers. PCR was performed to analyze the exons and flanking introns of the cardiac troponin T gene (TNNT2), beta-myosin heavy chain gene (MYH7), and myosin-binding protein C gene (MYBPC3) and the products were sequenced. The clinical data including symptom, physical examination, echocardiography and electrocardiography were collected. A 14035c > t mutation, which causes a missense mutation (R130C) in exon 10 of TNNT2 gene were identified in 4 family members, including the proband, female, aged 53, with the onset at the age of 30. The 4 persons with the 14035c > t mutation, all FHC patients, presented left ventricular dysfunction with a penetrance of 100%. Two of the patients died of sudden cardiac death during follow-up. No mutation was identified in the MYH7 and MYBPC3 genes. The 14035c > t mutation of TNNT2 gene is the causal mutation of FHC which is associated with malignant phenotype with a penetrance of 100%. It is a reasonable procedure in HCM patients with malignant phenotype to screen mutation in the TNNT2 gene. Show less

To compare the gene mutation between Chinese patients with familial and sporadic hypertrophic cardiomyopathy (HCM). Peripheral blood samples were collected from 36 patients with familial HCM (FHCM) and 50 patients with sporadic HCM (SHCM), all un-related and from different provinces of China. PCR was used to amplify the 26 protein-coding axons of beta-myosin heavy chain (MYH7), 16 exons for cardiac troponin T (TNNT2), and 38 exons for cardiac myosin-binding protein C (MYBPC3). The amplified products were sequenced and compared with the standard sequence in the genBank so as to determine the potential mutation sites. (1) 13 of the 36 FHCM patients (36.1%) harbored 3 different mutations in MYH7 gene: Arg663His in exon18, Glu924Lys in exon 23, and Ile736Thr in exon 20. Of the 50 SHCM patients, only 1 (2%) harbored MYH7 gene missence mutation: Ile736Thr located in exon 20. (2) TNNT2 was not identified in all SHCM patients and FHCM patients. (3) MYBPC3 was not identified in all SHCM patients. Four FHCM patients harbored 2 different mutations: Arg502Trp in exon 18 and Arg346fs in exon 13 respectively. MYH7 and MYBPC3 may be the dominant disease-causing genes in Chinese familial HCM patients; however the mutation rate of MYH7 and MYBPC3 genes is significantly lower in the SHCM patients compared with the FHCM patients. TNNT2 seems not the predominant disease-causing gene in all Chinese patients with HCM. Show less

To detect the disease-causing gene mutation of hypertrophic cardiomyopathy (HCM) in a Chinese family and to analyze the correlation of the genotype and the phenotype. One family affected with HCM was studied. The clinical data including symptom, physical examination, echocardiography and electrocardiography were collected. The full encoding exons and flanking sequences of beta-myosin heavy chain gene (MYH7) and cardiac myosin-binding protein C gene (MYBPC3) were amplified with PCR and the products were sequenced. A G8887A mutation, which is an acceptor splicing site of intron 15 (IVS15-1G > A) in MYBPC3 (gi: Y10129) was identified in 6 out of 11 family members. Three mutation carriers developed HCM at 48 - 75 years old with mild chest pain, chest distress and asymmetric septal hypertrophy (13 - 14 mm) and remaining mutation carriers are free of HCM. No mutation was identified in MYH7 gene. HCM caused by the IVS15-1G > A mutation is a benign phenotype. It is helpful to screen MYBPC3 gene mutation in late-onset HCM patients with mild symptoms. Show less

Mutations causing hypertrophic cardiomyopathy (HCM) have been described in nine different genes of the sarcomere. Three genes account for most known mutations: beta-myosin heavy chain (MYH7), cardiac myosin binding protein C (MYBPC3) and cardiac troponin T (TNNT2). Their prevalence in Italian HCM patients is unknown. Thus, we prospectively assessed a molecular screening strategy of these three genes in a consecutive population with HCM from two Italian centres. Comprehensive screening of MYBPC3, MYH7 and TNNT2 was performed in 88 unrelated HCM patients by denaturing high-performance liquid chromatography and automatic sequencing. We identified 32 mutations in 50 patients (57%); 16 were novel. The prevalence rates for MYBPC3, MYH7 and TNNT2 were 32%, 17% and 2%, respectively. MYBPC3 mutations were 18, including two frameshift, five splice-site and two nonsense. All were 'private' except insC1065 and R502Q, present in three and two patients, respectively. Moreover, E258K was found in 14% of patients, suggesting a founder effect. MYH7 mutations were 12, all missense; seven were novel. In TNNT2, only two mutations were found. In addition, five patients had a complex genotype [i.e. carried a double MYBPC3 mutation (n = 2), or were double heterozygous for mutations in MYBPC3 and MYH7 (n = 3)]. The first comprehensive evaluation of MYBPC3, MYH7 and TNNT2 in an Italian HCM population allowed a genetic diagnosis in 57% of the patients. These data support a combined analysis of the three major sarcomeric genes as a rational and cost-effective initial approach to the molecular screening of HCM. Show less

Mutations in sarcomere protein, PRKAG2, LAMP2, alpha-galactosidase A (GLA), and several mitochondrial genes can cause rare familial cardiomyopathies, but their contribution to increased left ventricular wall thickness (LVWT) in the community is unknown. We studied 1862 unrelated participants (52% women; age, 59+/-9 years) from the community-based Framingham Heart Study who had echocardiograms and provided DNA samples but did not have severe hypertension, aortic prosthesis, or significant aortic stenosis. Eight sarcomere protein genes, 3 storage cardiomyopathy-causing genes, and 27 mitochondrial genes were sequenced in unrelated individuals with increased LVWT (maximum LVWT >13 mm). Fifty eligible participants (9 women) had unexplained increased LVWT. We detected 8 mutations in 9 individuals (2 women); 7 mutations in 5 sarcomere protein genes (MYH7, MYBPC3, TNNT2, TNNI3, MYL3), and 1 GLA mutation. In individuals with increased LVWT, participants with sarcomere protein and storage mutations were clinically indistinguishable from those without mutations. In a community-based cohort, about 3% of eligible participants had increased LVWT, of whom 18% had sarcomere protein or lipid storage gene mutations. Increased LVWT in the community is a very heterogeneous condition, which sometimes may arise from single-gene variants in one of a number of genes. Show less