Multi-gene testing in neurological disorders showed an improved diagnostic yield: data from over 1000 Indian patients.

BACKGROUND: Neurological disorders are clinically heterogeneous group of disorders and are major causes of disability and death. Several of these disorders are caused due to genetic aberration. A precise and confirmatory diagnosis in the patients in a timely manner is essential for appropriate therapeutic and management strategies. Due to the complexity of the clinical presentations across various neurological disorders, arriving at an accurate diagnosis remains a challenge. METHODS: We sequenced 1012 unrelated patients from India with suspected neurological disorders, using TruSight One panel. Genetic variations were identified using the Strand NGS software and interpreted using the StrandOmics platform. RESULTS: We were able to detect mutations in 197 genes in 405 (40%) cases and 178 mutations were novel. The highest diagnostic rate was observed among patients with muscular dystrophy (64%) followed by leukodystrophy and ataxia (43%, each). In our cohort, 26% of the patients who received definitive diagnosis were primarily referred with complex neurological phenotypes with no suggestive diagnosis. In terms of mutations types, 62.8% were truncating and in addition, 13.4% were structural variants, which are also likely to cause loss of function. CONCLUSION: In our study, we observed an improved performance of multi-gene panel testing, with an overall diagnostic yield of 40%. Furthermore, we show that NGS (next-generation sequencing)-based testing is comprehensive and can detect all types of variants including structural variants. It can be considered as a single-platform genetic test for neurological disorders that can provide a swift and definitive diagnosis in a cost-effective manner.

Next-generation sequencing-based method shows increased mutation detection sensitivity in an Indian retinoblastoma cohort.

PURPOSE: Retinoblastoma (Rb) is the most common primary intraocular cancer of childhood and one of the major causes of blindness in children. India has the highest number of patients with Rb in the world. Mutations in the RB1 gene are the primary cause of Rb, and heterogeneous mutations are distributed throughout the entire length of the gene. Therefore, genetic testing requires screening of the entire gene, which by conventional sequencing is time consuming and expensive. METHODS: In this study, we screened the RB1 gene in the DNA isolated from blood or saliva samples of 50 unrelated patients with Rb using the TruSight Cancer panel. Next-generation sequencing (NGS) was done on the Illumina MiSeq platform. Genetic variations were identified using the Strand NGS software and interpreted using the StrandOmics platform. RESULTS: We were able to detect germline pathogenic mutations in 66% (33/50) of the cases, 12 of which were novel. We were able to detect all types of mutations, including missense, nonsense, splice site, indel, and structural variants. When we considered bilateral Rb cases only, the mutation detection rate increased to 100% (22/22). In unilateral Rb cases, the mutation detection rate was 30% (6/20). CONCLUSIONS: Our study suggests that NGS-based approaches increase the sensitivity of mutation detection in the RB1 gene, making it fast and cost-effective compared to the conventional tests performed in a reflex-testing mode.

Role of common sarcomeric gene polymorphisms in genetic susceptibility to left ventricular dysfunction.

Mutations in sarcomeric genes are common genetic cause of cardiomyopathies. An intronic 25-bp deletion in cardiac myosin binding protein C (MYBPC3) at 3' region is associated with dilated and hypertrophic cardiomyopathies in Southeast Asia. However, the frequency of sarcomeric gene polymorphisms and associated clinical presentation have not been established with left ventricular dysfunction (LVD). Therefore, the aim of the present study was to explore the association of MYBPC3 25-bp deletion, titin (TTN) 18 bp I/D, troponin T type 2 (TNNT2) 5 bp I/D and myospryn K2906N polymorphisms with LVD. This study includes 988 consecutive patients with angiographically confirmed coronary artery disease (CAD) and 300 healthy controls. Among the 988 CAD patients, 253 with reduced left ventricle ejection fraction (LVEF≤45%) were categorized as LVD. MYBPC3 25-bp deletion, TTN 18 bp I/D and TNNT2 5 bp I/D polymorphisms were determined by direct polymerase chain reaction method, while myospryn K2906N polymorphism by TaqMan assay. Our results showed that MYBPC3 25-bp deletion polymorphism was significantly associated with elevated risk of LVD (LVEF <45) (healthy controls versus LVD: OR=3.85, P <0.001; and nonLVD versus LVD: OR=1.65, P = 0.035), while TTN 18 bp I/D, TNNT2 5 bp I/D and myospryn K2906N polymorphisms did not show any significant association with LVD. The results also showed that MYBPC3 25-bp deletion polymorphism was significantly associated with other parameters of LV remodelling, i.e. LV dimensions (LV end diastole dimension, LVEDD: P = 0.037 and LV end systolic dimension, LVESD: P = 0.032). Our data suggests that MYBPC3 25-bp deletion may play significant role in conferring LVD as well as CAD risk in north Indian population.

Detection of high frequency of mutations in a breast and/or ovarian cancer cohort: implications of embracing a multi-gene panel in molecular diagnosis in India.

Breast and/or ovarian cancer (BOC) are among the most frequently diagnosed forms of hereditary cancers and leading cause of death in India. This emphasizes on the need for a cost-effective method for early detection of these cancers. We sequenced 141 unrelated patients and families with BOC using the TruSight Cancer panel, which includes 13 genes strongly associated with risk of inherited BOC. Multi-gene sequencing was done on the Illumina MiSeq platform. Genetic variations were identified using the Strand NGS software and interpreted using the StrandOmics platform. We were able to detect pathogenic mutations in 51 (36.2%) cases, out of which 19 were novel mutations. When we considered familial breast cancer cases only, the detection rate increased to 52%. When cases were stratified based on age of diagnosis into three categories, ⩽40 years, 40-50 years and >50 years, the detection rates were higher in the first two categories (44.4% and 53.4%, respectively) as compared with the third category, in which it was 26.9%. Our study suggests that next-generation sequencing-based multi-gene panels increase the sensitivity of mutation detection and help in identifying patients with a high risk of developing cancer as compared with sequential tests of individual genes.

Role of angiotensin II type I (AT1 A1166C) receptor polymorphism in susceptibility of left ventricular dysfunction.

BACKGROUND: Left ventricular dysfunction (LVD) with subsequent congestive heart failure (CHF) constitutes the final common pathway for a host of cardiac disorders. The impaired LV function develops in response to an ischemic insult followed by a fall in cardiac output that leads to activation of renin-angiotensin-system (RAS). Angiotensin II type I receptor (AT1), which mediate the vasoconstrictive and salt-conserving actions of the RAS, represent interesting candidate genes for cardiovascular diseases. Therefore, we conducted an association study between single nucleotide polymorphism (SNP) in AT1 gene and LVD in CAD patients. METHODS AND RESULTS: The present study recruited a total of 950 subjects including 720 angiography confirmed CAD patients and 230 healthy controls. Among 720 CAD patients, 229 with reduced left ventricle ejection fraction (LVEF≤45%) were categorized as LVD. The AT1 (A1166C, rs5186) polymorphism was determined by ARMS-PCR. Our results showed that the frequency of AT1 1166AC and CC genotypes were significantly higher in LVD patients in comparison to non-LVD (LVEF >45%) patients (p value = 0.003; OR = 1.81 and p value <0.001; OR = 4.33). Further analysis showed that AT1 A1166C polymorphism was significantly associated with LV end diastole (p-value = 0.031), end systole (p-value = 0.038) dimensions, and mean LVEF (p-value = 0.035). Moreover, on comparing the AT1 A1166C polymorphism in CAD patients with healthy controls, we did not find any association both at genotypic and allelic level (p value = 0.927; OR = 1.04 and p value = 0.219; OR = 0.83) respectively. CONCLUSIONS: Our study suggests that AT1 A1166C polymorphism may play significant role in conferring genetic susceptibility of LVD.

Matrix metalloproteinases in coronary artery disease.

Matrix metalloproteinases (MMP) are a family of zinc-containing endoproteinases that degrade extracellular matrix (ECM) components. MMP have important roles in the development, physiology and pathology of cardiovascular system. Metalloproteases also play key roles in adverse cardiovascular remodeling, atherosclerotic plaque formation and plaque instability, vascular smooth muscle cell (SMC) migration and restenosis that lead to coronary artery disease (CAD), and progressive heart failure. The study of MMP in developing animal model cardiovascular systems has been helpful in deciphering numerous pathologic conditions in humans. Increased peripheral blood MMP-2 and MMP-9 in acute coronary syndrome (ACS) may be useful as noninvasive tests for detection of plaque vulnerability. MMP function can be modulated by certain pharmacological drugs that can be exploited for treatment of ACS. CAD is a polygenic disease and hundreds of genes contribute toward its predisposition. A large number of sequence variations in MMP genes have been identified. Case-control association studies have highlighted their potential association with CAD and its clinical manifestations. Although results thus far are inconsistent, meta-analysis has demonstrated that MMP-3 Glu45Lys and MMP-9 1562C/T gene polymorphisms were associated with CAD risk.

Genetic predisposition to left ventricular dysfunction: a multigenic and multi-analytical approach.

BACKGROUND: Left ventricular dysfunction (LVD) is a complex, multifactorial condition, caused by mechanical, neurohormonal, and genetic factors. We have previously observed association of renin-angiotensin-aldosterone system (RAAS), matrix metalloproteinases (MMPs) and inflammatory pathway genes with LVD. Therefore the present study was undertaken to identify the combination of genetic variants and their possible interactions contributing towards genetic susceptibility to LVD in the background of coronary artery disease (CAD). METHODS AND RESULTS: The study included 230 healthy controls and 510 consecutive patients with angiographically confirmed CAD. Among them, 162 with reduced left ventricle ejection fraction (LVEF≤45%) were categorized as having LVD. We analyzed 11 polymorphisms of RAAS, MMPs and inflammatory pathways. Single locus analysis showed that AT1 A1166C (p value<0.001; OR=3.67), MMP9 R668Q (p value=0.007; OR=3.48) and NFKB1-94 ATTG ins/del (p value=0.013; OR=2.01) polymorphisms were independently associated with LVD when compared with both non-LVD patients and healthy controls. High-order gene-gene interaction analysis, using classification and regression tree (CART) and multifactor dimensionality reduction (MDR) revealed that AT1 A1166C and NFKB1-94 ATTG ins/del polymorphisms jointly increased the risk of LVD to great extent (p-value=0.001; OR=8.55) and best four-factor interaction model consisted of AT1 A1166C, MMP7 A-181G, MMP9 R668Q and NFKB1-94 ATTG ins/del polymorphisms with testing accuracy of 0.566 and cross validation consistency (CVC)=9/10 (permutation p<0.001) showed increased risk for LVD respectively. CONCLUSION: AT1 A1166C independently and in combination with MMP9 R668Q and NFKB1-94 ATTG ins/del polymorphisms plays important role in conferring genetic susceptibility to LVD in CAD patients.

Significant role of ADRB3 rs4994 towards the development of coronary artery disease.

BACKGROUND: Coronary artery disease (CAD) is the most common type of heart disease and cause of heart attacks. It has been proposed that both the susceptibility to disease and the interindividual variability in response to treatment relates in part to genetic polymorphisms, particularly those polymorphisms for neurotransmitter and drug receptors. Common functional polymorphisms in ß-adrenergic receptor genes (ADRB) have been associated with heart failure phenotypes. Therefore, the purpose of the present study was to explore the association of genetic variants in ADRB3 (C190T or Trp64Arg) ADRB1 (C1165G or Arg389Gly), and ADRA2A (C-1291G) with CAD. MATERIALS AND METHODS: The present study recruited a total of 600 consecutive patients with angiographically confirmed CAD and 200 population-matched controls (173 men and 27 women) (mean age 54.10±8.30 years). The ADRB3 T190C, ADRA2A C-1291G, and ADRB1 C1165G polymorphisms were determined by PCR-restriction fragment length polymorphism. The putative functional effects were determined in the coding region of the ADRD3 gene by online web servers FASTSNP and F-SNP. RESULTS: On comparing the genotype frequency distribution in CAD patients with that of healthy individuals, significant association was observed with the CC genotype of the ADRB3 T190C polymorphism (P=0.040, odds ratio=1.5). Also, at the allelic level the C allele of ADRB3 T190C conferred risk for CAD (P=0.005, odds ratio=1.7). The ADRA2A C-1291G and ADRB1 C1165G polymorphisms were not found to be a risk for CAD when compared with controls. CONCLUSION: The present study finding suggests that ADRB3 C190T may also be involved in the complex pathophysiology of CAD.

Association of angiotensin I-converting enzyme gene insertion/deletion polymorphism with rheumatic heart disease in Indian population and meta-analysis.

Rheumatic heart disease (RHD) is one of the most severe consequences of rheumatic fever. It has been suggested that angiotensin I-converting enzyme (ACE) may be involved in the increased valvular fibrosis and calcification in the pathogenesis of RHD. We conducted a case-control study to look for association of ACE I/D polymorphism with RHD in Indian population. The study incorporated 300 patients (170 males and 130 females) with RHD, and 200 controls (118 males and 82 females). We also subgrouped RHD patients into mitral valve lesion (MVL) and combined valve lesion (CVL). ACE I/D polymorphism was identified using polymerase chain reaction method. We also performed a meta-analysis of three published studies and the present study (636 RHD cases and 533 controls) to evaluate the association between the ACE I/D polymorphisms and RHD risk. A significant difference in ACE ID and DD genotypes distribution between RHD cases (OR = 1.62, 95% CI = 1.11-2.36 and OR = 2.08, 95% CI = 1.02-4.15, respectively) and corresponding controls was observed. On comparing the ACE genotypes of MVL and CVL subgroups with controls, ID and DD genotypes were also significantly associated with CVL (FDR Pcorr = 0.009, OR = 2.19 and FDR Pcorr = 0.014, OR = 3.29, respectively). Meta-analysis also suggested association of the ACE D allele (FDR Pcorr = 0.036, OR-1.22, 95% CI 1.02-1.45) with RHD. In conclusion, ACE ID and DD genotypes are associated with an increased risk of RHD, particularly CVL. This suggests that the ACE I/D gene polymorphism may play an important role in the pathogenesis of RHD.

Multi-analytic approach elucidates significant role of hormonal and hepatocanalicular transporter genetic variants in gallstone disease in North Indian population.

OBJECTIVE: Cholesterol gallstone disease (CGD) is a multifactorial and multistep disease. Apart from female gender and increasing age being the documented non-modifiable risk factor for gallstones the pathobiological mechanisms underlying the phenotypic expression of CGD appear to be rather complex, and one or more variations in genes could play critical roles in the diverse pathways further progressing to cholesterol crystal formation. In the present study we performed genotyping score, Multifactor dimensionality reduction (MDR) and Classification and Regression Tree analysis (CART) to identify combinations of alleles among the hormonal, hepatocanalicular transporter and adipogenesis differentiation pathway genes in modifying the risk for CGD. DESIGN: The present case-control study recruited total of 450 subjects, including 230 CGD patients and 220 controls. We analyzed common ESR1, ESR2, PGR, ADRB3, ADRA2A, ABCG8, SLCO1B1, PPARγ2, and SREBP2 gene polymorphisms to find out combinations of genetic variants contributing to CGD risk, using multi-analytical approaches (G-score, MDR, and CART). RESULTS: Single locus analysis by logistic regression showed association of ESR1 IVS1-397C>T (rs2234693), IVS1-351A>G (rs9340799) PGR ins/del (rs1042838) ADRB3-190 T>C (rs4994) ABCG8 D19H (rs11887534), SLCO1B1 Exon4 C>A (rs11045819) and SREBP2 1784G>C (rs2228314) with CGD risk. However, the MDR and CART analysis revealed ESR1 IVS1-397C>T (rs2234693) ADRB3-190 T>C (rs4994) and ABCG8 D19H (rs11887534) polymorphisms as the best polymorphic signature for discriminating between cases and controls. The overall odds ratio for the applied multi-analytical approaches ranged from 4.33 to 10.05 showing an incremental risk for cholesterol crystal formation. In conclusion, our muti-analytical approach suggests that, ESR1, ADRB3, in addition to ABCG8 genetic variants confer significant risk for cholesterol gallstone disease.

Role of inflammatory gene polymorphisms in left ventricular dysfunction (LVD) susceptibility in coronary artery disease (CAD) patients.

RATIONALE: Inflammation exacerbates a number of deleterious effects on the heart, most notable being left ventricular dysfunction (LVD). A promoter polymorphism of the NFKB1 gene (encodes p50 subunit) results in lower protein levels of NFkB p50 subunits, which in its dimmer (p50) form has anti-inflammatory effects. The active NFkB transcription factor promotes the expression of over 150 target genes including IL6 and TNF-α. Therefore, the aim of the present study was to assess the association of NFKB1, IL6 and TNF-α gene polymorphisms with LVD in coronary artery disease (CAD) patients. METHODS AND RESULTS: The present study included a total of 830 subjects (600 CAD patients and 230 controls) and was carried out in two (primary and replication) cohorts. CAD patients with reduced left ventricle ejection fraction (LVEF ≤45%) were categorized having LVD. The NFKB1 -94 ATTG ins/del (rs28362491), IL6 -174 G/C (rs1800795) and TNF-α -308 G/A (rs1800629) polymorphisms were genotyped by PCR/ARMS-PCR methods. The results of the primary cohort were validated in a replicative cohort and pooled by meta-analysis using Fisher's and Mantel-Haenszel test. The analysis showed that NFKB1 ATTG/ATTG genotype was significantly associated with LVD (Fisher's method p-value=0.007, Mantel-Haenszel OR=2.34), LV end diastole (p-value=0.013), end systole (p-value=0.011) dimensions, LV mass (p-value=0.024), mean LVEF (p-value=0.001) and myocardial infarction (p-value=0.043). CONCLUSION: Our data suggests that NFKB1 -94 ATTG ins/del polymorphism plays significant role in conferring susceptibility of LVD and ATTG/ATTG genotype may modulate risk of heart failure by increasing ventricular remodeling and worsening LV function.

Association of matrix metalloproteinases (MMP2, MMP7 and MMP9) genetic variants with left ventricular dysfunction in coronary artery disease patients.

BACKGROUND: Left ventricular dysfunction (LVD) is a condition resulting from clustered structural or functional cardiac disorder that reduces the ability of the ventricle to fill with or eject blood. The impaired ventricular function can be attributed to unfavorable ventricular remodeling. Among the pathways that contribute to remodeling process, matrix metalloproteinases (MMPs) appear to be of particular interest. We explored the association of MMP2 (C-735T, rs2285053), MMP7 (A-181G, rs11568818) and MMP9 (R279Q, rs17576), (P574R, rs2250889), (R668Q, rs17577) genetic variants with LVD in coronary artery disease (CAD) patients. METHODS: The study included 310 consecutive patients with angiographically confirmed CAD and 230 healthy controls. Among patients with CAD, 95 with reduced left ventricle ejection fraction (LVEF ≤ 45) were categorized as LVD. Polymorphisms were determined by PCR-RFLP. RESULTS: The MMP9 R668Q genetic variant was significantly associated with LVD (LVEF ≤ 45) (p value=0.009; OR=3.82). To validate our results, we performed a replication study in additional 200 cases with similar clinical characteristics and results again confirmed consistent findings (p value=0.033; OR=3.59). Also the frequency of haplotype R,P,Q comprising R668Q variation in MMP 9 was significantly higher in reduced LVEF subjects (p value=0.008; OR=1.83). CONCLUSION: MMP9 R668Q plays important role in conferring susceptibility of LVD.

Impact of renin-angiotensin-aldosterone system gene polymorphisms on left ventricular dysfunction in coronary artery disease patients.

BACKGROUND: Left ventricular dysfunction (LVD), followed by fall in cardiac output is one of the major complications in some coronary artery disease (CAD) patients. The decreased cardiac output over time leads to activation of the renin-angiotensin-aldosterone system which results in vasoconstriction by influencing salt-water homeostasis. Therefore, the purpose of the present study was to explore the association of single nucleotide polymorphisms (SNPs) in angiotensin I converting enzyme; ACE (rs4340), angiotensin II type1 receptor; AT1 (rs5186) and aldosterone synthase; CYP11B2 (rs1799998) with LVD. METHODS AND RESULTS: The present study was carried out in two cohorts. The primary cohort included 308 consecutive patients with angiographically confirmed CAD and 234 healthy controls. Among CAD, 94 with compromised left ventricle ejection fraction (LVEF ⩽ 45) were categorized as LVD. The ACE I/D, AT1 A1166C and CYP11B2 T-344C polymorphisms were determined by PCR. Our results showed that ACE I/D was significantly associated with CAD but not with LVD. However, AT1 1166C variant was significantly associated with LVD (LVEF ⩽ 45) (p value=0.013; OR=3.69), but CYP11B2 (rs1799998) was not associated with either CAD or LVD. To validate our results, we performed a replication study in additional 200 cases with similar clinical characteristics and results again confirmed consistent findings (p value=0.020; OR=5.20). CONCLUSION: AT1 A1166C plays important role in conferring susceptibility of LVD.