A p.R870H mutation in the beta-cardiac myosin heavy chain 7 gene causes familial hypertrophic cardiomyopathy in several members of an Indian family

Return of Participants' Incidental Genetic Research Findings: Experience from a Case-Control Study of Asthma in an American Indian Community

The proper communication of clinically actionable findings to participants of genetic research entails important ethical considerations, but has been challenging for a variety of reasons. We document an instance of the return of individual genetic results in the context of a very rural American Indian community, in hopes of providing insight to other investigators about potentially superior or inferior courses of action. This was a case/control study of asthma among 324 pediatric participants. Subsequently, microarray genotype data became available, providing over 2 million variants, incidentally including some conferring risk for conditions for which the American College of Medical Genetics recommends return of results. The study investigators engaged in extensive consultation with the IRB, the tribal government, and local clinicians to better inform our approach. We were able to notify the two participants heterozygous for the one clinically actionable variant identified. One participant welcomed this information and proceeded to obtain further clinical work-up; the other participant declined further follow-up. While demanding considerable time and effort, the return of clinically actionable genetic results is important from both an ethical perspective and to provide an improved trust relationship with the community of research participants.

Sarcomeric gene variants among Indians with hypertrophic cardiomyopathy: A scoping review

Hypertrophic cardiomyopathy (HCM) is a genetic heart muscle disease that frequently causes sudden cardiac death (SCD) among young adults. Several pathogenic mutations in genes encoding the cardiac sarcomere have been identified as diagnostic factors for HCM and proposed as prognostic markers for SCD. The objective of this review was to determine the scope of available literature on the variants encoding sarcomere proteins associated with SCD reported among Indian patients with HCM. The eligibility criteria for the scoping review included full text articles that reported the results of genetic screening for sarcomeric gene mutations in HCM patients of Indian south Asian ancestry. We systematically reviewed studies from the databases of Medline, Scopus, Web of Science core collection and Google Scholar. The electronic search strategy included a combination of generic terms related to genetics, disease and population. The protocol of the study was registered with Open Science Framework (https://osf.io/53gde/). A total of 19 articles were identified that reported pathogenic or likely pathogenic (P/LP) variants within MYH7, MYBPC3, TNNT2, TNNI3 and TPM1 genes, that included 16 singletons, one de novo and one digenic mutation (MYH7/ TPM1) associated with SCD among Indian patients. Evidence from functional studies and familial segregation implied a plausible mechanistic role of these P/LP variants in HCM pathology. This scoping review has compiled all the P/LP variants reported to-date among Indian patients and summarized their association with SCD. Single homozygous, de novo and digenic mutations were observed to be associated with severe phenotypes compared to single heterozygous mutations. The abstracted genetic information was updated with reference sequence ID (rsIDs) and compiled into freely accessible HCMvar database, available at https://hcmvar.heartfailure.org.in/. This can be used as a population specific genetic database for reference by clinicians and researchers involved in the identification of diagnostic and prognostic markers for HCM.

Return of Participants' Incidental Genetic Research Findings: Experience from a Case-Control Study of Asthma in an American Indian Community

PURPOSE

The proper communication of clinically actionable findings to participants of genetic research entails important ethical considerations, but has been challenging for a variety of reasons. We document an instance of return of individual genetic results in the context of a very rural American Indian community, in hopes of providing insight to other investigators about potentially superior or inferior courses of action.

METHODS

The original study was a case/control study of asthma among 324 pediatric participants. The study utilized a genotyping microarray assessing over 2 million variants, including one conferring risk for hypertrophic cardiomyopathy for which the American College of Medical Genetics recommends return of results to participants. The study investigators engaged in extensive consultation with the IRB, the Tribal government and local clinicians to better inform our approach.

RESULTS

With some difficulty we were able to notify the 2 participants heterozygous for this variant. One participant welcomed this information and proceeded to obtain further clinical work-up; the other participant declined further follow-up.

CONCLUSION

While demanding of considerable time and effort, the return of clinically actionable genetic results is important from both an ethical perspective and to provide an improved trust relationship with the community of research participants.

Phenotype variation of hypertrophic cardiomyopathy in carriers of the p.Arg870His pathogenic variant in the MYH7 gene

The review analyzes variability of clinical manifestations of p.Arg870His in the MYH7 gene, which is repeatedly registered in patients with hypertrophic cardiomyopathy (HCM). The analysis involves the data from scientific publications obtained as a search result in the PubMed, СlinVar, and eLibrary.ru databases, as well as authors’ own results. A wide range of phenotypic manifestations have been revealed in carriers of p.Arg870His, from the asymptomatic to severe course, rapid progression, and early death. The review considers possible factors that modify the effect of the pathogenic variant (i.e. dosage of the pathogenic variant, the presence of other unfavorable genetic variants, etc.). The importance of accumulating information on the clinical features of HCM in the carriers of specific gene variants is emphasized in order to clarify their pathogenicity and to identify factors modifying the clinical outcome, which is important for the choice of the treatment strategy for HCM.

Recent Advances in the Molecular Genetics of Familial Hypertrophic Cardiomyopathy in South Asian Descendants

The South Asian population, numbered at 1.8 billion, is estimated to comprise around 20% of the global population and 1% of the American population, and has one of the highest rates of cardiovascular disease. While South Asians show increased classical risk factors for developing heart failure, the role of population-specific genetic risk factors has not yet been examined for this group. Hypertrophic cardiomyopathy (HCM) is one of the major cardiac genetic disorders among South Asians, leading to contractile dysfunction, heart failure, and sudden cardiac death. This disease displays autosomal dominant inheritance, and it is associated with a large number of variants in both sarcomeric and non-sarcomeric proteins. The South Asians, a population with large ethnic diversity, potentially carries region-specific polymorphisms. There is high variability in disease penetrance and phenotypic expression of variants associated with HCM. Thus, extensive studies are required to decipher pathogenicity and the physiological mechanisms of these variants, as well as the contribution of modifier genes and environmental factors to disease phenotypes. Conducting genotype-phenotype correlation studies will lead to improved understanding of HCM and, consequently, improved treatment options for this high-risk population. The objective of this review is to report the history of cardiovascular disease and HCM in South Asians, present previously published pathogenic variants, and introduce current efforts to study HCM using induced pluripotent stem cell-derived cardiomyocytes, next-generation sequencing, and gene editing technologies. The authors ultimately hope that this review will stimulate further research, drive novel discoveries, and contribute to the development of personalized medicine with the aim of expanding therapeutic strategies for HCM.

A systematic review and meta-analysis of genotype-phenotype associations in patients with hypertrophic cardiomyopathy caused by sarcomeric protein mutations

BACKGROUND

The genetic basis of familial hypertrophic cardiomyopathy (HCM) is well described, but the relation between genotype and clinical phenotype is still poorly characterised.

OBJECTIVE

To summarise and critically review the current literature on genotype-phenotype associations in patients with HCM and to perform a meta-analysis on selected clinical features.

DATA SOURCES

PubMed/Medline was searched up to January 2013. Retrieved articles were checked for additional publications.

SELECTION CRITERIA

Observational, cross-sectional and prospectively designed English language human studies that analysed the relationship between the presence of mutations in sarcomeric protein genes and clinical parameters.

DATA EXTRACTION AND ANALYSIS

The pooled analysis was confined to studies reporting on cohorts of unrelated and consecutive patients in which at least two sarcomere genes were sequenced. A random effect meta-regression model was used to determine the overall prevalence of predefined clinical features: age at presentation, gender, family history of HCM, family history of sudden cardiac death (SCD), and maximum left ventricular wall thickness (MLVWT). The I(2) statistic was used to estimate the proportion of total variability in the prevalence data attributable to the heterogeneity between studies.

RESULTS

Eighteen publications (corresponding to a total of 2459 patients) were selected for the pooled analysis. The presence of any sarcomere gene mutation was associated with a younger age at presentation (38.4 vs 46.0 years, p<0.0005), a family history of HCM (50.6% vs 23.1%, p<0.0005), a family history of SCD (27.0% vs 14.9%, p<0.0005) and greater MLVWT (21.0 vs 19.3 mm, p=0.03). There were no differences when the two most frequently affected genes, MYBPC3 and MYH7, were compared. A total of 53 family studies were also included in the review. These were characterised by pronounced variability and the majority of studies reporting on outcomes analysed small cross-sectional cohorts and were unsuitable for pooled analyses.

CONCLUSIONS

The presence of a mutation in any sarcomere gene is associated with a number of clinical features. The heterogeneous nature of the disease and the inconsistency of study design precludes the establishment of more precise genotype-phenotype relationships. Large scale studies examining the relation between genotype, disease severity, and prognosis are required.

A low prevalence of MYH7/MYBPC3 mutations among familial hypertrophic cardiomyopathy patients in India

Familial Hypertrophic Cardiomyopathy (FHC) is an autosomal dominant disorder affecting the cardiac muscle and exhibits varied clinical symptoms because of genetic heterogeneity. Several disease causing genes have been identified and most code for sarcomere proteins. In the current study, we have carried out clinical and molecular analysis of FHC patients from India. FHC was detected using echocardiography and by analysis of clinical symptoms and family history. Disease causing mutations in the β-cardiac myosin heavy chain (MYH7) and Myosin binding protein C3 (MYBPC3) genes were identified using Polymerase Chain Reaction-Deoxyribose Nucleic Acid (PCR-DNA) sequencing. Of the 55 patient samples screened, mutations were detected in only nineteen in the two genes; MYBPC3 mutations were identified in 12 patients while MYH7 mutations were identified in five, two patients exhibited double heterozygosity. All four MYH7 mutations were missense mutations, whereas only 3/9 MYPBC3 mutations were missense mutations. Four novel mutations in MYBPC3 viz. c.456delC, c.2128G>A (p.E710K), c.3641G>A (p.W1214X), and c.3656T>C (p.L1219P) and one in MYH7 viz. c.965C>T (p.S322F) were identified. A majority of missense mutations affected conserved amino acid residues and were predicted to alter the structure of the corresponding mutant proteins. The study has revealed a greater frequency of occurrence of MYBPC3 mutations when compared to MYH7 mutations.

The MYH7 p.R787H mutation causes hypertrophic cardiomyopathy in two unrelated families

BACKGROUND

Familial hypertrophic cardiomyopathy (FHC) is a Mendelian disorder usually caused by mutations in any one of more than 12 genes, most of which encode sarcomere proteins. The disease exhibits extensive genetic heterogeneity, and it is important to identify mutations that result in adverse symptoms and/or lethality in affected individuals. An analysis of disease-causing mutations has been initiated in the Indian population to determine prevalent mutations.

METHODS

FHC was detected using echocardiography and by analysis of clinical symptoms and family history. The disease-causing mutation was identified using polymerase chain reaction DNA sequencing.

RESULTS

The p.R787H mutation was identified in the MYH7 gene in two FHC families. Sequence and structure analysis suggested impaired binding of the mutant protein to the myosin essential light chain.

CONCLUSIONS

Although the mutation results in variable clinical symptoms in the affected individuals, probably owing to the effect of modifier genes and/or environmental factors, it does not appear to be a lethal mutation.

Genotype phenotype correlations of cardiac beta-myosin heavy chain mutations in Indian patients with hypertrophic and dilated cardiomyopathy

The aim of the current study was to determine the frequency of mutations in the beta-myosin heavy chain gene (MYH7) in a cohort of hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) and their families, and to investigate correlations between genotype and phenotype. About 130 consecutive patients diagnosed with HCM or DCM (69 with HCM and 61 with DCM) attending the cardiology clinic of Post Graduate Institute of Medical Education and Research were screened for mutations in the MYH7 gene. The control group for genetic studies consisted of 100 healthy subjects. We report 14 mutations in 6 probands (5 probands in HCM and 1 proband in DCM) and their family members. Out of these 6 mutations, 3 are new and are being reported for the first time. One known mutation (p.Gly716Arg) was found to be "de novo" which resulted in severe asymmetric septal hypertrophy (31 mm) and resulted in the sudden cardiac death (SCD) of the proband at the age of 21 years. Further, a DCM causing novel mutation p.Gly377Ser was identified which resulted in the milder phenotype. The present study shows that there is genetic and phenotypic heterogeneity of cardiomyopathies in Indian population. Further, the location and type of mutation in a given sarcomeric gene determines the severity and phenotypic plasticity in cardiomyopathies.