Sleep fragmentation induces heart failure in a hypertrophic cardiomyopathy mouse model by altering redox metabolism

Sleep fragmentation (SF) disrupts normal biological rhythms and has major impacts on cardiovascular health; however, it has never been shown to be a risk factor involved in the transition from cardiac hypertrophy to heart failure (HF). We now demonstrate devastating effects of SF on hypertrophic cardiomyopathy (HCM). We generated a transgenic mouse model harboring a patient-specific myosin binding protein C3 (MYBPC3) variant displaying HCM, and measured the progression of pathophysiology in the presence and absence of SF. SF induces mitochondrial damage, sarcomere disarray, and apoptosis in HCM mice; these changes result in a transition of hypertrophy to an HF phenotype by chiefly targeting redox metabolic pathways. Our findings for the first time show that SF is a risk factor for HF transition and have important implications in clinical settings where HCM patients with sleep disorders have worse prognosis, and strategic intervention with regularized sleep patterns might help such patients.

Cardiomyocyte orientation recovery at micrometer scale reveals long-axis fiber continuum in heart walls

Coordinated cardiomyocyte contraction drives the mammalian heart to beat and circulate blood. No consensus model of cardiomyocyte geometrical arrangement exists, due to the limited spatial resolution of whole heart imaging methods and the piecemeal nature of studies based on histological sections. By combining microscopy and computer vision, we produced the first-ever three-dimensional cardiomyocyte orientation reconstruction across mouse ventricular walls at the micrometer scale, representing a gain of three orders of magnitude in spatial resolution. We recovered a cardiomyocyte arrangement aligned to the long-axis direction of the outer ventricular walls. This cellular network lies in a thin shell and forms a continuum with longitudinally arranged cardiomyocytes in the inner walls, with a complex geometry at the apex. Our reconstruction methods can be applied at fine spatial scales to further understanding of heart wall electrical function and mechanics, and set the stage for the study of micron-scale fiber remodeling in heart disease.

Novel MYBPC3 Mutations in Indian Population with Cardiomyopathies

Background

Mutations in Myosin Binding Protein C (MYBPC3) are one of the most frequent causes of cardiomyopathies in the world, but not much data are available in India.

Methods

We carried out targeted direct sequencing of MYBPC3 in 115 hypertrophic (HCM) and 127 dilated (DCM) cardiomyopathies against 197 ethnically matched healthy controls from India.

Results

We detected 34 single nucleotide variations in MYBPC3, of which 19 were novel. We found a splice site mutation [(IVS6+2T) T>G] and 16 missense mutations in Indian cardiomyopathies [5 in HCM; E258K, T262S, H287L, R408M, V483A: 4 in DCM; T146N, V321L, A392T, E393K and 7 in both HCM and DCM; L104M, V158M, S236G, R272C, T290A, G522E, A626V], but those were absent in 197 normal healthy controls. Interestingly, we found 7 out of 16 missense mutations (V158M, E258K, R272C, A392T, V483A, G522E, and A626V) in MYBPC3 were altering the evolutionarily conserved native amino acids, accounted for 8.7% and 6.3% in HCM and DCM, respectively. The bioinformatic tools predicted that those 7 missense mutations were pathogenic. Moreover, the co-segregation of those 7 mutations in families further confirmed their pathogenicity. Remarkably, we also identified compound mutations within the MYBPC3 gene of 6 cardiomyopathy patients (5%) with more severe disease phenotype; of which, 3 were HCM (2.6%) [(1. K244K + E258K + (IVS6+2T) T>G); (2. L104M + G522E + A626V); (3. P186P + G522E + A626V]; and 3 were DCM (2.4%) [(1. 5'UTR + A392T; 2. V158M+G522E; and 3.V158M + T262T + A626V].

Conclusion

The present comprehensive study on MYBPC3 has revealed both single and compound mutations in MYBPC3 and their association with disease in Indian Population with Cardiomyopathies. Our findings may perhaps help in initiating diagnostic strategies and eventually recognizing the targets for therapeutic interventions.

Mindin (SPON2) Is Essential for Cutaneous Fibrogenesis in a Mouse Model of Systemic Sclerosis

Systemic sclerosis is a fibrotic disease that initiates in the skin and progresses to internal organs, leading to a poor prognosis. Unraveling the etiology of a chronic, multifactorial disease such as systemic sclerosis has been aided by various animal models that recapitulate certain aspects of the human pathology. We found that the transcription factor SNAI1 is overexpressed in the epidermis of patients with systemic sclerosis, and a transgenic mouse recapitulating this expression pattern is sufficient to induce many clinical features of the human disease. Using this mouse model as a discovery platform, we have uncovered a critical role for the matricellular protein Mindin (SPON2) in fibrogenesis. Mindin is produced by SNAI1 transgenic skin keratinocytes and aids fibrogenesis by inducing early inflammatory cytokine production and collagen secretion in resident dermal fibroblasts. Given the dispensability of Mindin in normal tissue physiology, targeting this protein holds promise as an effective therapy for fibrosis.

Generation of a new human induced pluripotent stem cell (hiPSC) line from a South Asian Indian with a MYBPC3Δ25bp variant

Myosin binding protein C3 (MYBPC3) is a thick filament contractile protein that interacts with myosin, titin and actin and regulates cardiac muscle contraction. Genetic variations in the MYBPC3 gene are known causal factors for cardiomyopathy and heart failure. Previously, we identified a recurrent MYBPC3 deletion (25 base pairs) among South Asians associated with cardiomyopathy and heart failure. Here, we generated an induced pluripotent stem cell (iPSC) line using peripheral blood mononuclear cells (PBMC) from an Indian harboring MYBPC3 deletion. This iPSC line displayed embryonic stem cell morphology, expressed pluripotency markers, differentiated into three germ layers and exhibited normal karyotype.

Ribosomal protein S6 kinase beta-1 gene variants cause hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is a genetic heart muscle disease with preserved or increased ejection fraction in the absence of secondary causes. Mutations in the sarcomeric protein-encoding genes predominantly cause HCM. However, relatively little is known about the genetic impact of signalling proteins on HCM.

METHODS AND RESULTS

Here, using exome and targeted sequencing methods, we analysed two independent cohorts comprising 401 Indian patients with HCM and 3521 Indian controls. We identified novel variants in ribosomal protein S6 kinase beta-1 (RPS6KB1 or S6K1) gene in two unrelated Indian families as a potential candidate gene for HCM. The two unrelated HCM families had the same heterozygous missense S6K1 variant (p.G47W). In a replication association study, we identified two S6K1 heterozygotes variants (p.Q49K and p.Y62H) in the UK Biobank cardiomyopathy cohort (n=190) compared with matched controls (n=16 479). These variants are neither detected in region-specific controls nor in the human population genome data. Additionally, we observed an S6K1 variant (p.P445S) in an Arab patient with HCM. Functional consequences were evaluated using representative S6K1 mutated proteins compared with wild type in cellular models. The mutated proteins activated the S6K1 and hyperphosphorylated the rpS6 and ERK1/2 signalling cascades, suggesting a gain-of-function effect.

CONCLUSIONS

Our study demonstrates for the first time that the variants in the S6K1 gene are associated with HCM, and early detection of the S6K1 variant carriers can help to identify family members at risk and subsequent preventive measures. Further screening in patients with HCM with different ethnic populations will establish the specificity and frequency of S6K1 gene variants.

Heterogeneous Distribution of Genetic Mutations in Myosin Binding Protein-C Paralogs

Myosin binding protein-C (MyBP-C) is a sarcomeric protein which regulates the force of contraction in striated muscles. Mutations in the MYBPC family of genes, including slow skeletal (MYBPC1), fast skeletal (MYBPC2) and cardiac (MYBPC3), can result in cardiac and skeletal myopathies. Nonetheless, their evolutionary pattern, pathogenicity and impact on MyBP-C protein structure remain to be elucidated. Therefore, the present study aimed to systematically assess the evolutionarily conserved and epigenetic patterns of MYBPC family mutations. Leveraging a machine learning (ML) approach, the Genome Aggregation Database (gnomAD) provided variants in MYBPC1, MYBPC2, and MYBPC3 genes. This was followed by an analysis with Ensembl’s variant effect predictor (VEP), resulting in the identification of 8,618, 3,871, and 3,071 variants in MYBPC1, MYBPC2, and MYBPC3, respectively. Missense variants comprised 61%–66% of total variants in which the third nucleotide positions in the codons were highly altered. Arginine was the most mutated amino acid, important because most disease-causing mutations in MyBP-C proteins are arginine in origin. Domains C5 and C6 of MyBP-C were found to be hotspots for most mutations in the MyBP-C family of proteins. A high percentage of truncated mutations in cMyBP-C cause cardiomyopathies. Arginine and glutamate were the top hits in fMyBP-C and cMyBP-C, respectively, and tryptophan and tyrosine were the most common among the three paralogs changing to premature stop codons and causing protein truncations at the carboxyl terminus. A heterogeneous epigenetic pattern was identified among the three MYBP-C paralogs. Overall, it was shown that databases using computational approaches can facilitate diagnosis and drug discovery to treat muscle disorders caused by MYBPC mutations.

Whole genome sequencing delineates regulatory, copy number, and cryptic splice variants in early onset cardiomyopathy

Cardiomyopathy (CMP) is a heritable disorder. Over 50% of cases are gene-elusive on clinical gene panel testing. The contribution of variants in non-coding DNA elements that result in cryptic splicing and regulate gene expression has not been explored. We analyzed whole-genome sequencing (WGS) data in a discovery cohort of 209 pediatric CMP patients and 1953 independent replication genomes and exomes. We searched for protein-coding variants, and non-coding variants predicted to affect the function or expression of genes. Thirty-nine percent of cases harbored pathogenic coding variants in known CMP genes, and 5% harbored high-risk loss-of-function (LoF) variants in additional candidate CMP genes. Fifteen percent harbored high-risk regulatory variants in promoters and enhancers of CMP genes (odds ratio 2.25, p = 6.70 × 10-7 versus controls). Genes involved in α-dystroglycan glycosylation (FKTN, DTNA) and desmosomal signaling (DSC2, DSG2) were most highly enriched for regulatory variants (odds ratio 6.7-58.1). Functional effects were confirmed in patient myocardium and reporter assays in human cardiomyocytes, and in zebrafish CRISPR knockouts. We provide strong evidence for the genomic contribution of functionally active variants in new genes and in regulatory elements of known CMP genes to early onset CMP.

Novel Mutations in β-MYH7 Gene in Indian Patients With Dilated Cardiomyopathy

Background

Methods

Results

Conclusions

Adiponectin receptor 1 variants contribute to hypertrophic cardiomyopathy that can be reversed by rapamycin

Hypertrophic cardiomyopathy (HCM) is a heterogeneous genetic heart muscle disease characterized by hypertrophy with preserved or increased ejection fraction in the absence of secondary causes. However, recent studies have demonstrated that a substantial proportion of individuals with HCM also have comorbid diabetes mellitus (~10%). Whether genetic variants may contribute a combined phenotype of HCM and diabetes mellitus is not known. Here, using next-generation sequencing methods, we identified novel and ultrarare variants in adiponectin receptor 1 (ADIPOR1) as risk factors for HCM. Biochemical studies showed that ADIPOR1 variants dysregulate glucose and lipid metabolism and cause cardiac hypertrophy through the p38/mammalian target of rapamycin and/or extracellular signal-regulated kinase pathways. A transgenic mouse model expressing an ADIPOR1 variant displayed cardiomyopathy that recapitulated the cellular findings, and these features were rescued by rapamycin. Our results provide the first evidence that ADIPOR1 variants can cause HCM and provide new insights into ADIPOR1 regulation.

VEGFA Promoter Polymorphisms rs699947 and rs35569394 Are Associated With the Risk of Anterior Cruciate Ligament Ruptures Among Indian Athletes: A Cross-sectional Study

Background:

Associations of genetic variants within certain fibril-forming genes have previously been observed with anterior cruciate ligament (ACL) injuries. Evidence suggests a significant role of angiogenesis-associated cytokines in remodeling the ligament fibril matrix after mechanical loading and maintaining structural and functional integrity of the ligament. Functional polymorphisms within the vascular endothelial growth factor A (VEGFA) gene have emerged as plausible candidates owing to their role in the regulation of angiogenic responses.

Hypothesis:

VEGFA promoter polymorphisms rs699947 and rs35569394 are associated with ACL injury risk among athletes.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

A total of 90 Indian athletes with radiologically confirmed or surgically proven isolated ACL tears and 76 matched-control athletes were selected for the present cross-sectional genetic association study. Oral mouthwash samples were collected from all the case and control athletes and genotyped for VEGFA rs699947 and rs35569394 using the polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) method.

Results:

The A allele (rs699947) was significantly overrepresented in the ACL group (C vs A allele: odds ratio [OR], 1.68 [95% CI, 1.08-2.60]; P = .021) (CC vs CA + AA: OR, 2.69 [95% CI, 1.37-5.26]; P = .004). There was a greater frequency of the AA genotype in the ACL group in comparison with the control group (OR, 3.38 [95% CI, 1.23-9.28]; P = .016) when only male athletes were compared. Likewise, there was a greater frequency of the I allele (rs35569394) in the ACL group (D vs I allele: OR, 1.64 [95% CI, 1.06-2.55]; P = .025) (DD vs ID + II: OR, 2.61 [95% CI, 1.31-5.21]; P = .006). The A-I haplotype was overrepresented in the ACL group compared with the control group (OR, 1.68 [95% CI, 1.08-2.60]; χ² = 5.320; P = .021), and both the polymorphisms were found to be in complete linkage disequilibrium (r² = 0.929; logarithm of the odds score = 63.74; D′ = 1.0). Female athletes did not show any difference in genotype or allele frequency.

Conclusion:

This is the first study to investigate the association of VEGFA promoter polymorphisms in ACL tears among Indian athletes. Increased frequencies of the A allele (rs699947) and I allele (rs35569394) were observed in the ACL group. These results suggest that sequence variants in the VEGF gene are associated with ACL injury risk among athletes. Further research with long-term follow-ups measuring VEGF expression levels during recovery is warranted to establish its role in ACL injuries and healing.

A field-based quantitative analysis of sublethal effects of air pollution on pollinators

While the impact of air pollution on human health is well studied, mechanistic impacts of air pollution on wild systems, including those providing essential ecosystem services, are largely unknown, but directly impact our health and well-being. India is the world's largest fruit producer, second most populous country, and contains 9 of the world's 10 most polluted cities. Here, we sampled Giant Asian honey bees, Apis dorsata, at locations with varying air pollution levels in Bangalore, India. We observed significant correlations between increased respirable suspended particulate matter (RSPM) deposition and changes in bee survival, flower visitation, heart rate, hemocyte levels, and expression of genes related to lipid metabolism, stress, and immunity. Lab-reared Drosophila melanogaster exposed to these same sites also exhibited similar molecular and physiological differences. Our study offers a quantitative analysis on the current impacts of air pollution on insects, and indicates the urgency for more nonhuman studies to accurately assess the effects of pollution on our natural world.

Genetic, clinical, molecular, and pathogenic aspects of the South Asian-specific polymorphic MYBPC3Δ25bp variant

Hypertrophic cardiomyopathy (HCM) is a cardiac genetic disease characterized by ventricular enlargement, diastolic dysfunction, and increased risk for sudden cardiac death. Sarcomeric genetic defects are the predominant known cause of HCM. In particular, mutations in the myosin-binding protein C gene (MYBPC3) are associated with ~ 40% of all HCM cases in which a genetic basis has been established. A decade ago, our group reported a 25-base pair deletion in intron 32 of MYBPC3 (MYBPC3Δ25bp) that is uniquely prevalent in South Asians and is associated with autosomal dominant cardiomyopathy. Although our studies suggest that this deletion results in left ventricular dysfunction, cardiomyopathies, and heart failure, the precise mechanism by which this variant predisposes to heart disease remains unclear. Increasingly appreciated, however, is the contribution of secondary risk factors, additional mutations, and lifestyle choices in augmenting or modifying the HCM phenotype in MYBPC3Δ25bp carriers. Therefore, the goal of this review article is to summarize the current research dedicated to understanding the molecular pathophysiology of HCM in South Asians with the MYBPC3Δ25bp variant. An emphasis is to review the latest techniques currently applied to explore the MYBPC3Δ25bp pathogenesis and to provide a foundation for developing new diagnostic strategies and advances in therapeutics.

Myocardin ablation in a cardiac-renal rat model

Cardiorenal syndrome is defined by primary heart failure conditions influencing or leading to renal injury or dysfunction. Dilated cardiomyopathy (DCM) is a major co-existing form of heart failure (HF) with renal diseases. Myocardin (MYOCD), a cardiac-specific co-activator of serum response factor (SRF), is increased in DCM porcine and patient cardiac tissues and plays a crucial role in the pathophysiology of DCM. Inhibiting the increased MYOCD has shown to be partially rescuing the DCM phenotype in porcine model. However, expression levels of MYOCD in the cardiac tissues of the cardiorenal syndromic patients and the effect of inhibiting MYOCD in a cardiorenal syndrome model remains to be explored. Here, we analyzed the expression levels of MYOCD in the DCM patients with and without renal diseases. We also explored, whether cardiac specific silencing of MYOCD expression could ameliorate the cardiac remodeling and improve cardiac function in a renal artery ligated rat model (RAL). We observed an increase in MYOCD levels in the endomyocardial biopsies of DCM patients associated with renal failure compared to DCM alone. Silencing of MYOCD in RAL rats by a cardiac homing peptide conjugated MYOCD siRNA resulted in attenuation of cardiac hypertrophy, fibrosis and restoration of the left ventricular functions. Our data suggest hyper-activation of MYOCD in the pathogenesis of the cardiorenal failure cases. Also, MYOCD silencing showed beneficial effects by rescuing cardiac hypertrophy, fibrosis, size and function in a cardiorenal rat model.

Mitochondrial genome variations in idiopathic dilated cardiomyopathy

Idiopathic dilated cardiomyopathy (DCM) is a structural heart disease with strong genetic background. The aim of this study was to assess the role of mitochondrial DNA (mtDNA) variations and haplogroups in Indian DCM patients. Whole mtDNA analysis of 221 DCM patients revealed 48 novel, 42 disease-associated and 97 private variations. The frequency of reported variations associated with hearing impairment, DEAF, SNHL and LHON are significantly high in DCM patients than controls. Haplogroups H and HV were over represented in DCM than controls. Functional analysis of two private variations (m.8812A>G & m.10320G>A) showed decrease in mitochondrial functions, suggesting the role of mtDNA variations in DCM.

Evolutionary conserved networks of human height identify multiple Mendelian causes of short stature

Height is a heritable and highly heterogeneous trait. Short stature affects 3% of the population and in most cases is genetic in origin. After excluding known causes, 67% of affected individuals remain without diagnosis. To identify novel candidate genes for short stature, we performed exome sequencing in 254 unrelated families with short stature of unknown cause and identified variants in 63 candidate genes in 92 (36%) independent families. Based on systematic characterization of variants and functional analysis including expression in chondrocytes, we classified 13 genes as strong candidates. Whereas variants in at least two families were detected for all 13 candidates, two genes had variants in 6 (UBR4) and 8 (LAMA5) families, respectively. To facilitate their characterization, we established a clustered network of 1025 known growth and short stature genes, which yielded 29 significantly enriched clusters, including skeletal system development, appendage development, metabolic processes, and ciliopathy. Eleven of the candidate genes mapped to 21 of these clusters, including CPZ, EDEM3, FBRS, IFT81, KCND1, PLXNA3, RASA3, SLC7A8, UBR4, USP45, and ZFHX3. Fifty additional growth-related candidates we identified await confirmation in other affected families. Our study identifies Mendelian forms of growth retardation as an important component of idiopathic short stature.

Abstract 484: Mir-19b-3p Regulates Autophagy by Targeting Raf-1 During Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a heterogenous disease predominantly caused by sarcomeric genes. However, 40-50% cases etiology are not known. RAF1 mutations cause syndromic and isolated childhood cardiomyopathies. Functional mutations in untranslated regions (UTRs) of RAF-1 gene are rare, and their role in cardiomyopathy is unexplored. UTRs are important sites for interaction of epigenetic regulators such as microRNAs (miR). miRs have exhibited as crucial regulators of the cardiac remodeling process. We identified a novel mutation in RAF-1 3’-UTR (an important site for binding of miR-19a-3p/19b-3p) in large family members associated with HCM. Whole exome sequencing revealed that these family members are negative for mutations in known cardiomyopathy associated genes. miR-19a/b are known to play a crucial role in cardiac hypertrophy. The aim of this study is to determine the role of miR-19a-3p/19b-3p in regulating RAF-1 expression and delineating the molecular and functional consequences of identified RAF-1 3’-UTR mutation. Our results show that the overexpression of miR-19b-3p, leads to downregulation of RAF-1 expression and regulation. Notably, miR-19b-3p was found to be pro-hypertrophic as its overexpression resulted in increasing hypertrophic markers including ANP and β-MHC expression. Moreover, findings from experiments using RAF1 +/+ and RAF1 -/- mouse embryo fibroblasts (MEFs) confirms the role of miR-19b-3p interaction and regulation of RAF-1 signaling axis. Interestingly, we also observed many autophagy markers (Atg3, Atg 12-5 complex, and LC3 II) are dysregulated by miR-19-b-3p overexpression. Our study uncovers a novel mechanism through which miR-19b-3p regulates autophagy by targeting RAF-1.

Melatonin and Human Cardiovascular Disease

The possible therapeutic role of melatonin in the pathophysiology of coronary artery disorder (CAD) is increasingly being recognized. In humans, exogenous melatonin has been shown to decrease nocturnal hypertension, improve systolic and diastolic blood pressure, reduce the pulsatility index in the internal carotid artery, decrease platelet aggregation, and reduce serum catecholamine levels. Low circulating levels of melatonin are reported in individuals with CAD, arterial hypertension, and congestive heart failure. This review assesses current literature on the cardiovascular effects of melatonin in humans. It can be concluded that melatonin deserves to be considered in clinical trials evaluating novel therapeutic interventions for cardiovascular disorders.

Myeloid Dysregulation in a Human Induced Pluripotent Stem Cell Model of PTPN11-Associated Juvenile Myelomonocytic Leukemia

Somatic PTPN11 mutations cause juvenile myelomonocytic leukemia (JMML). Germline PTPN11 defects cause Noonan syndrome (NS), and specific inherited mutations cause NS/JMML. Here, we report that hematopoietic cells differentiated from human induced pluripotent stem cells (hiPSCs) harboring NS/JMML-causing PTPN11 mutations recapitulated JMML features. hiPSC-derived NS/JMML myeloid cells exhibited increased signaling through STAT5 and upregulation of miR-223 and miR-15a. Similarly, miR-223 and miR-15a were upregulated in 11/19 JMML bone marrow mononuclear cells harboring PTPN11 mutations, but not those without PTPN11 defects. Reducing miR-223's function in NS/JMML hiPSCs normalized myelogenesis. MicroRNA target gene expression levels were reduced in hiPSC-derived myeloid cells as well as in JMML cells with PTPN11 mutations. Thus, studying an inherited human cancer syndrome with hiPSCs illuminated early oncogenesis prior to the accumulation of secondary genomic alterations, enabling us to discover microRNA dysregulation, establishing a genotype-phenotype association for JMML and providing therapeutic targets.

Dominant negative Ras attenuates pathological ventricular remodeling in pressure overload cardiac hypertrophy

The importance of the oncogene Ras in cardiac hypertrophy is well appreciated. The hypertrophic effects of the constitutively active mutant Ras-Val12 are revealed by clinical syndromes due to the Ras mutations and experimental studies. We examined the possible anti-hypertrophic effect of Ras inhibition in vitro using rat neonatal cardiomyocytes (NRCM) and in vivo in the setting of pressure-overload left ventricular (LV) hypertrophy (POH) in rats. Ras functions were modulated via adenovirus directed gene transfer of active mutant Ras-Val12 or dominant negative mutant N17-DN-Ras (DN-Ras). Ras-Val12 expression in vitro activates NFAT resulting in pro-hypertrophic and cardio-toxic effects on NRCM beating and Z-line organization. In contrast, the DN-Ras was antihypertrophic on NRCM, inhibited NFAT and exerted cardio-protective effects attested by preserved NRCM beating and Z line structure. Additional experiments with silencing H-Ras gene strategy corroborated the antihypertrophic effects of siRNA-H-Ras on NRCM. In vivo, with the POH model, both Ras mutants were associated with similar hypertrophy two weeks after simultaneous induction of POH and Ras-mutant gene transfer. However, LV diameters were higher and LV fractional shortening lower in the Ras-Val12 group compared to control and DN-Ras. Moreover, DN-Ras reduced the cross-sectional area of cardiomyocytes in vivo, and decreased the expression of markers of pathologic cardiac hypertrophy. In isolated adult cardiomyocytes after 2 weeks of POH and Ras-mutant gene transfer, DN-Ras improved sarcomere shortening and calcium transients compared to Ras-Val12. Overall, DN-Ras promotes a more physiological form of hypertrophy, suggesting an interesting therapeutic target for pathological cardiac hypertrophy.

Coexistence of Digenic Mutations in Both Thin (TPM1) and Thick (MYH7) Filaments of Sarcomeric Genes Leads to Severe Hypertrophic Cardiomyopathy in a South Indian FHCM

Mutations in sarcomeric genes are the leading cause for cardiomyopathies. However, not many genetic studies have been carried out on Indian cardiomyopathy patients. We performed sequence analyses of a thin filament sarcomeric gene, α-tropomyosin (TPM1), in 101 hypertrophic cardiomyopathy (HCM) patients and 147 dilated cardiomyopathy (DCM) patients against 207 ethnically matched healthy controls, revealing 13 single nucleotide polymorphisms (SNPs). Of these, one mutant, S215L, was identified in two unrelated HCM cases-patient #1, aged 44, and patient #2, aged 65-and was cosegregating with disease in these families as an autosomal dominant trait. In contrast, S215L was completely absent in 147 DCM and 207 controls. Patient #1 showed a more severe disease phenotype, with poor prognosis and a family history of sudden cardiac death, than patient #2. Therefore, these two patients and the family members positive for S215L were further screened for variations in MYH7, MYBPC3, TNNT2, TNNI3, MYL2, MYL3, and ACTC. Interestingly, two novel thick filaments, D896N (homozygous) and I524K (heterozygous) mutations, in the MYH7 gene were identified exclusively in patient #1 and his family members. Thus, we strongly suggest that the coexistence of these digenic mutations is rare, but leads to severe hypertrophy in a South Indian familial hypertrophic cardiomyopathy (FHCM).

A novel arginine to tryptophan (R144W) mutation in troponin T (cTnT) gene in an indian multigenerational family with dilated cardiomyopathy (FDCM)

Cardiomyopathy is a major cause of heart failure and sudden cardiac death; several mutations in sarcomeric protein genes have been associated with this disease. Our aim in the present study is to investigate the genetic variations in Troponin T (cTnT) gene and its association with dilated cardiomyopathy (DCM) in south-Indian patients. Analyses of all the exons and exon-intron boundaries of cTnT in 147 DCM and in 207 healthy controls had revealed a total of 15 SNPs and a 5 bp INDEL; of which, polymorphic SNPs were compared with the HapMap population data. Interestingly, a novel R144W mutation, that substitutes polar-neutral tryptophan for a highly conserved basic arginine in cTnT, altering the charge drastically, was identified in a DCM, with a family history of sudden-cardiac death (SCD). This mutation was found within the tropomyosin (TPM1) binding domain, and was evolutionarily conserved across species, therefore it is expected to have a significant impact on the structure and function of the protein. Family studies had revealed that the R144W is co-segregating with disease in the family as an autosomal dominant trait, but it was completely absent in 207 healthy controls and in 162 previously studied HCM patients. Further screening of the proband and three of his family members (positive for R144W mutant) with eight other genes β-MYH7, MYBPC3, TPM1, TNNI3, TTN, ACTC, MYL2 and MYL3, did not reveal any disease causing mutation, proposing the absence of compound heterozygosity. Therefore, we strongly suggest that the novel R144W unique/private mutant identified in this study is associated with FDCM. This is furthermore signifying the unique genetic architecture of Indian population.

RAF1 mutations in childhood-onset dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a highly heterogeneous trait with sarcomeric gene mutations predominating. The cause of a substantial percentage of DCMs remains unknown, and no gene-specific therapy is available. On the basis of resequencing of 513 DCM cases and 1,150 matched controls from various cohorts of distinct ancestry, we discovered rare, functional RAF1 mutations in 3 of the cohorts (South Indian, North Indian and Japanese). The prevalence of RAF1 mutations was ~9% in childhood-onset DCM cases in these three cohorts. Biochemical studies showed that DCM-associated RAF1 mutants had altered kinase activity, resulting in largely unaltered ERK activation but in AKT that was hyperactivated in a BRAF-dependent manner. Constitutive expression of these mutants in zebrafish embryos resulted in a heart failure phenotype with AKT hyperactivation that was rescued by treatment with rapamycin. These findings provide new mechanistic insights and potential therapeutic targets for RAF1-associated DCM and further expand the clinical spectrum of RAF1-related human disorders.

Cardiac Troponin T (TNNT2) mutations are less prevalent in Indian hypertrophic cardiomyopathy patients

We sought to determine the frequency of the genetic variations in the Troponin T (TNNT2) gene and its association in Indian cardiomyopathy patients. Sequencing of the entire TNNT2 gene in 162 hypertrophic cardiomyopathy (HCM) patients, along with 179 healthy controls, revealed a total of 15 variants. These included an A28V missense mutation, a novel single-nucleotide polymorphism (SNP) (g.7239;G→A) predicted to disturb the splicing significantly, three SNPs, rs3729547 (C→T), rs3729843 (G→A), rs3729842 (C→T), which were in high linkage disequilibrium, and a 5 bp polymorphism that skipped exon 4 during splicing, which was found to be significantly higher in HCM patients (del/del genotype, p=0.00011; deletion allele, p=0.00008). Further studies on the 5 bp polymorphism in 2092 randomly selected individuals belonging to 39 ethnic and endogamous populations from 19 states of India, and representing the major linguistic Indian families, revealed that the South and the Northwest Indians have a high frequency of 5 bp deletions. The missense mutations in TNNT2 are responsible for 15%-20% of familial HCM by impairing the function of the heart muscle. However, other than the 5 bp polymorphism, our comprehensive study on the Indian HCM patients have lowered the occurrence and overall prevalence of supposedly more aggressive and worst disease causing percentage of missense mutations in TNNT2 dramatically.

Cyclosporine attenuates cardiomyocyte hypertrophy induced by RAF1 mutants in Noonan and LEOPARD syndromes

RAS activation is implicated in physiologic and pathologic cardiac hypertrophy. Cross-talk between the Ras and calcineurin pathways, the latter also having been implicated in cardiac hypertrophy, has been suspected for pathologic hypertrophy. Our recent discovery that germ-line mutations in RAF1, which encodes a downstream RAS effector, cause Noonan and LEOPARD syndromes with a high prevalence of hypertrophic cardiomyopathy provided an opportunity to elaborate the role of RAF1 in cardiomyocyte biology. Here, we characterize the role of RAF1 signaling in cardiomyocyte hypertrophy with an aim of identifying potential therapeutic targets. We modeled hypertrophic cardiomyopathy by infecting neonatal and adult rat cardiomyocytes (NRCMs and ARCMs, respectively) with adenoviruses encoding wild-type RAF1 and three Noonan/LEOPARD syndrome-associated RAF1 mutants (S257L, D486N or L613V). These RAF1 proteins, except D486N, engendered cardiomyocyte hypertrophy. Surprisingly, these effects were independent and dependent of mitogen activated protein kinases in NRCMs and ARCMs, respectively. Inhibiting Mek1/2 in RAF1 overexpressing cells blocked hypertrophy in ARCMs but not in NRCMs. Further, we found that endogenous and heterologously expressed RAF1 complexed with calcineurin, and RAF1 mutants causing hypertrophy signaled via nuclear factor of activated T cells (Nfat) in both cell types. The involvement of calcineurin was also reflected by down regulation of Serca2a and dysregulation of calcium signaling in NRCMs. Furthermore, treatment with the calcineurin inhibitor cyclosporine blocked hypertrophy in NRCMs and ARCMs overexpressing RAF1. Thus, we have identified calcineurin as a novel interaction partner for RAF1 and established a mechanistic link and possible therapeutic target for pathological cardiomyocyte hypertrophy induced by mutant RAF1. This article is part of a Special Issue entitled 'Possible Editorial'.

Targeted genome-wide enrichment of functional regions

Only a small fraction of large genomes such as that of the human contains the functional regions such as the exons, promoters, and polyA sites. A platform technique for selective enrichment of functional genomic regions will enable several next-generation sequencing applications that include the discovery of causal mutations for disease and drug response. Here, we describe a powerful platform technique, termed “functional genomic fingerprinting” (FGF), for the multiplexed genomewide isolation and analysis of targeted regions such as the exome, promoterome, or exon splice enhancers. The technique employs a fixed part of a uniquely designed Fixed-Randomized primer, while the randomized part contains all the possible sequence permutations. The Fixed-Randomized primers bind with full sequence complementarity at multiple sites where the fixed sequence (such as the splice signals) occurs within the genome, and multiplex amplify many regions bounded by the fixed sequences (e.g., exons). Notably, validation of this technique using cardiac myosin binding protein-C (MYBPC3) gene as an example strongly supports the application and efficacy of this method. Further, assisted by genomewide computational analyses of such sequences, the FGF technique may provide a unique platform for high-throughput sample production and analysis of targeted genomic regions by the next-generation sequencing techniques, with powerful applications in discovering disease and drug response genes.

Mitochondrial DNA haplogroup 'R' is associated with Noonan syndrome of south India

Mutations in PTPN11 gene was responsible for approximately 50% of the Noonan syndrome (NS), however, we did not find any mutation in PTPN11 in any of seven NS patients analysed. Whereas, the complete mtDNA sequencing revealed 146 mutations, of which five, including one heteroplasmic (A11144R; Thr-->Ala) non-synonymous mutation, were novel and exclusively observed in NS patients. Interestingly all the seven probands and their maternal relatives were clustered under a major haplogroup R and its novel sub-haplogroups (R7b1b, R30a1, R30c, T2b7, U9a1) exclusive in NS, therefore we strongly suggest that these haplogroups may influence NS in South Indian populations.

Novel mitochondrial DNA mutations implicated in Noonan syndrome

We report a case of Noonan syndrome with compound mutations in a sarcomeric contractile protein gene and several novel mutations in mitochondrial genes. Our case forms the first report, which emphasizes the importance of mtDNA mutations in Noonan syndrome and extends the scope for mitochondrial related syndromes.

Cardiac isoform of alpha 2 macroglobulin, an early diagnostic marker for cardiac manifestations in AIDS patients

This study investigated the possible role of the cardiac isoform of alpha 2-macroglobulin (CA2M) as an early diagnostic marker for HIV-associated cardiovascular manifestations. A total of 349 samples were analysed by Western blot and quantified by sandwich enzyme-linked immunosorbent assay. The levels of CA2M present in sera of HIV-associated cardiac diseases were significantly higher than those of HIV without cardiac involvement and healthy sera. CA2M may act as a novel diagnostic marker to identify cardiac manifestations in HIV/AIDS patients.

Cardiac isoform of alpha-2 macroglobulin—A new biomarker for myocardial infarcted diabetic patients

Cardiac isoform of alpha-2 macroglobulin [cardiac alpha2M] has been shown to be an early marker in cardiac hypertrophy and left ventricular mass in humans. We, here, for the first time report its presence in myocardial infarcted humans and tried to explore the possibility of using this protein as a novel diagnostic marker for myocardial infarcted diabetic patients. A total of 260 samples were analyzed in this study for the presence of cardiac alpha2M. These include 55 patients of diabetic with post myocardial infarction [PMI], 45 diabetic patients without PMI, 60 patients of PMI alone and 100 controls without any ailments. Levels of cardiac alpha2M present in the sera of diabetic patients with PMI are significantly higher than that of normal human sera and diabetic patients without PMI but not with PMI alone group, suggesting this protein as a marker for PMI itself. However, our results reveal that cardiac alpha2M could be a valuable marker for the diagnosis of myocardial infarcted diabetic patients and differentiating them from diabetic patients without myocardial infarction by sandwich ELISA.

Cardiac isoform of alpha-2 macroglobulin as a novel diagnostic marker for cardiac diseases

BACKGROUND

Earlier we showed cardiac isoform of alpha-2 macroglobulin (CA2M) to be an early marker of cardiac hypertrophy.

DESIGN

In this study, we tried to explore the possibility of using this protein as a marker for diagnosis of cardiac diseases.

METHODS

A total of 593 samples were analyzed for the presence of CA2M using sandwich enzyme-linked immunosorbent assay.

RESULTS

Samples include various cardiac diseases (230), non-cardiac ailments (263) and controls (100).

CONCLUSION

Levels of CA2M in cardiac diseases were significantly higher than other sample groups but moderately elevated in leprosy. This protein could be considered for diagnosis of cardiac diseases as a serum marker.