Pratibha Nallari

Genes governing premature ovarian failure

Premature ovarian failure (POF) is unexplained amenorrhoea (>6 months), increased FSH (>20 IU/l) and LH occurring before 40 years. Several genes are reported as having significance in POF, including genes governing regulation of the hypothalamic-pituitary-ovarian axis, but their role in ovarian physiology is not known. Deletions or translocations in Xq arm have been found to be associated with POF, assuming presence of ovarian-related genes but ovary-related function of these genes is unclear. Several researchers have suggested specific loci on Xq critical region, POF1 and POF2 and genes DIA, FMR1 and FMR2. The understanding of ovarian physiology, its regulation and genes involved is important to explain the causes of POF. Some genes coordinate development of germ cell to primordial stage, e.g. GDF9, BMP15 and NGF, while others regulate development of further stages, such as FSH and LH. Mutation in these genes may lead to female infertility and are likely to be candidate genes for POF. Recently, association between blepharophimosis-ptosis-epicanthus inversus syndrome type 1 and POF has emerged as a possibility. Galactosaemia is also shown to be important in POF due to toxic effects of accumulated galactose or downstream products. Thus, understanding the role of several genes can be used for the appropriate genetic diagnosis, research and in the clinical practice of POF.

Molecular genetics of familial hypertrophic cardiomyopathy (FHC).

AbstractFamilial hypertrophic cardiomyopathy is an autosomal dominant disease with a wide range of clinical features from benign to severe, and is the most common cause of sudden death in otherwise healthy individuals. The two prominent clinical features are left ventricular hypertrophy and myocyte/myofibrillar disarray. The former is responsible for clinical symptoms such as breathlessness and angina, whereas the latter may lead to sudden cardiac death. The last decade has seen an enormous improvement in our understanding of the molecular genetics of this disorder. The clinical heterogeneity has been linked to genetic heterogeneity; mutations in nine genes encoding sarcomere proteins have been shown to be the molecular basis for the disorder. However, attempts to establish a genotype-phenotype correlation for each of the more than 100 mutations that have been identified have not been highly successful. Additional genetic loci, as well as nongenetic factors such as lifestyle, sex, and age, have also been shown to play a role in modulating the clinical presentation of the disease. How each mutation results in hypertrophy and/or myofibrillar disarray is unclear. The present review discusses the current status of the molecular genetic characterization of this important disorder.

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.

Serum vitamin D levels and VDR polymorphisms (BsmI and FokI) in patients and their household contacts susceptible to tuberculosis.

Vitamin D, an immunomodulator of macrophage function, can activate human antimycobacterial activity. Vitamin D deficiency (VDD) is associated with an impaired mycobacterial immunity and susceptibility to tuberculosis. It has been found that vitamin D and its receptor may be essential for immune function. In this study, we examined the serum 25(OH) vitamin D levels and its receptor (VDR) polymorphisms with susceptibility to tuberculosis in patients, household contacts and healthy controls. Serum 25(OH) vitamin D levels were measured in 75 cases (25 patients, 25 household contacts and 25 healthy controls), and polymorphisms (BsmI and FokI) were carried out in 335 cases (110 patients, 110 household contacts and 115 healthy controls). The proportion of serum 25(OH) vitamin D deficiency and insufficiency was high in patients (44, 58%) and household contacts (40, 48%) compared to controls (48%). The BB and Bb genotypes of BsmI were significantly associated in patients (P < 0.014; OR: 0.509; CI: 0.265–0.876) (P < 0.001; OR: 2.351; CI: 1.368–4.041) and household contacts (P < 0.04; OR: 0.575; CI: 0.336–0.985); (P < 0.002; OR: −2.267; CI: 1.32–3.895) when compared to healthy controls. The diplotype and MDR analysis showed the high‐risk genotypes of BsmI and FokI polymorphisms. Vitamin D deficiency and its association with VDR gene polymorphisms may be useful to identify the high‐risk group individuals.

Role of IL-10 -819(T/C) Promoter Polymorphism in Preeclampsia

Abstract—Preeclampsia is a severe complication of pregnancy characterized by an excessive maternal systemic inflammatory response with activation of both the innate and adaptive immune system. Interleukin-10 affects maternal intravascular inflammation, as well as endothelial dysfunction. The aim of the study was to investigate the association between IL-10 T-819 C polymorphism and preeclampsia. A total of 120 pregnant women with preeclampsia and 120 women with normal pregnancy attending the Gynecological Unit of Government Maternity Hospital, Petlaburz, Hyderabad, India, were considered for the present study. A standard amplification refractory mutation system (ARMS) PCR was carried out for genotyping of IL-10 T-819 C promoter polymorphism in all the participants. Genotypic distribution of the control and patient groups was compared with values predicted by the Hardy-Weinberg equilibrium using χ2 test. Odds ratios (OR) and their respective 95 % confidence intervals were used to measure the strength of association between IL-10 gene polymorphism and preeclampsia. The frequencies of IL-10 T-819 C genotypes, CC, CT, and TT, were 47.5, 28.3, and 24.2 % in women with preeclampsia and 20.8, 48.3, and 30.8 % in the controls, respectively. There is a significant difference in the distribution of genotypes and alleles of IL-10 T-819 C between the two groups (test power = 0.66). The present study suggests that the IL-10 T-819 C gene promoter polymorphism can be a major genetic regulator in the etiology of preeclampsia

Role of transforming growth factor-β1 −509 C/T promoter polymorphism in gastric cancer in south Indian population

Gastric cancer is a multifactorial disease with the involvement of both genetic and environmental risk factors. Genetic variation in genes encoding cytokines and their receptors determine the intensity of the inflammatory response, which may contribute to individual differences in the outcome and severity of the disease. Transforming growth factor (TGF-β) signaling pathway plays an important role in the genesis and progression of tumors through regulating cell proliferation and differentiation. A hospital-based case–control study was conducted to investigate whether TGF-β1 −509 C/T polymorphism can modify the risk of gastric cancer. Seventy endoscopically and histopathologically confirmed gastric cancer patients and 100 age and sex-matched healthy controls were enrolled in the case–control study. TGF-β1 −509 C/T gene polymorphism was carried out by amplification refractory mutation system polymerase chain reaction (ARMS-PCR) method followed by agarose gel electrophoresis. Statistical analysis was applied to test for the significance of the results. The distribution of TGF-β1 genotypes at −509 C/T were CC 37.14%, CT 50%, and TT 12.86% in gastric cancer patients and CC 52%, CT 42%, and TT 6% in control subjects. The allelic frequencies of C and T were 0.621 and 0.379 in gastric cancer patients and 0.73 and 0.27 in control subjects, respectively. Our study imply that T allele of TGF-β1 −509 C/T genotypes may be a risk factor of genetic susceptibility to gastric cancer in south Indian population.

Haplotypes of NOS3 Gene Polymorphisms in Dilated Cardiomyopathy

Dilated Cardiomyopathy (DCM) is characterized by systolic dysfunction, followed by heart failure necessitating cardiac transplantation. The genetic basis is well established by the identification of mutations in sarcomere and cytoskeleton gene/s. Modifier genes and environmental factors are also considered to play a significant role in the variable expression of the disease, hence various mechanisms are implicated and one such mechanism is oxidative stress. Nitric Oxide (NO), a primary physiological transmitter derived from endothelium seems to play a composite role with diverse anti-atherogenic effects as vasodilator. Three functional polymorphisms of endothelial nitric oxide synthase (NOS3) gene viz., T-786C of the 5′ flanking region, 27bp VNTR in intron4 and G894T of exon 7 were genotyped to identify their role in DCM. A total of 115 DCM samples and 454 controls were included. Genotyping was carried out by PCR -RFLP method. Allelic and genotypic frequencies were computed in both control & patient groups and appropriate statistical tests were employed. A significant association of TC genotype (T-786C) with an odds ratio of 1.74, (95% CI 1.14 - 2.67, p = 0.01) was observed in DCM. Likewise the GT genotypic frequency of G894T polymorphism was found to be statistically significant (OR 2.10, 95% CI 1.34–3.27, p = 0.0011), with the recessive allele T being significantly associated with DCM (OR 1.64, 95% CI 1.18 - 2.30, p = 0.003). The haplotype carrying the recessive alleles of G894T and T-786C, C4bT was found to exhibit 7 folds increased risk for DCM compared to the controls. Hence C4bT haplotype could be the risk haplotype for DCM. Our findings suggest the possible implication of NOS3 gene in the disease phenotype, wherein NOS3 may be synergistically functioning in DCM associated heart failure via the excessive production of NO in cardiomyocytes resulting in decreased myocardial contractility and systolic dysfunction, a common feature of DCM phenotype.

Etiopathogenesis of arrhythmogenic right ventricular cardiomyopathy

AbstractArrhythmogenic right ventricular cardiomyopathy (ARVC) is characterised by progressive fibro-fatty replacement of right ventricular myocardium. Earlier studies described ARVC as non-inflammatory, non-coronary disorder associated with arrhythmias, heart failure and sudden death due to functional exclusion of the right ventricle. Molecular genetic studies have identified nine different loci associated with ARVC; accordingly each locus is implicated for each type of ARVC (ARVC1-ARVC9). So far five genes have been identified as containing pathogenic mutations for ARVC. Though mutations in each of the gene/s indicate disruption of different pathways leading to the condition, the exact pathogenesis of the condition is still obscure. This review tries to understand the pathogenesis of the condition by examining the individual proteins implicated and relate them to the pathways that could play a role in the aetiology of the condition. Cardiac ryanodine receptor (RYR-2), which regulates intra-cellular Ca2+ concentration by releasing Ca2+ reserves from the sarcoplasmic reticulum (SR), was the first gene for ARVC. The mutation in this gene is believed to disrupt coupled gating of RYR-2, causing after-depolarisation, leading to arrhythmias followed by structural changes due to altered intra-cellular Ca2+ levels. Three other genes implicated for ARVC, plakoglobin (Naxos disease), desmoplakin (ARVC8) and plakophilin (ARVC9) have prompted the speculation that ARVC is primarily a disease of desmosomes. But identification of TGFβ-3 for ARVC1 and the role of all these three genes (plakoglobin, desmoplakin and plakophilin) in cardiac morphogenesis indicate some kind of signal-transducing pathway disruption in the condition. The finding that ARVC as a milder form of Uhls anomaly indicates similar ontogeny for the condition. Further, discovery of apoptotic cells in the autopsy of the right ventricular myocardium of ARVC patients does indicate a common pathway for different types of ARVCs, which is more specific for the right ventricular myocardium involving desmosomal plaque proteins, growth factors and Ca2+ receptors.

MYBPC3 gene variations in hypertrophic cardiomyopathy patients in India

BACKGROUND 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. OBJECTIVE To screen exons 16, 18, 19, 22, 24, 28, 30, 31 and 34 in the MYBPC3 gene in Indian HCM patients. METHODS 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. RESULTS 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. CONCLUSION 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.

Endothelin 1 gene as a modifier in dilated cardiomyopathy.

Dilated cardiomyopathy (DCM) is a myocardial disease of unknown etiology with left ventricular dilatation and impaired myocardial contractility leading to heart failure. It is considered to be a multifactorial disorder with the interplay of both genetic and environmental factors. One of the possible genes implicated in DCM is endothelin 1 (EDN1). The genetic variants of EDN1 may be involved in the pathophysiology of DCM hence the entire EDN1 gene was screened to examine for the possible genotypic associations with DCM. A total of 115 DCM patients and 250 control subjects were included in the present study. PCR based SSCP analysis was carried out followed by commercial sequencing. Screening of EDN1 revealed two common and two rare polymorphisms. Allelic and genotypic frequencies were estimated in patient and control groups by appropriate statistical tests. The heterozygotes of insertion variation (+138A) were found to exhibit four-fold increase risk to DCM (OR=4.12, 95% CI 2.10-8.08; p=0.0001). The two rare variants (G>A transition (rs150035515) at c.90 and C>T transition (rs149399492) at c.119) observed in the present study were found to be unique in DCM. The secondary mRNA structures of these variations were found to have less free energy than wild type. The haplotype analysis revealed 4A-T to be risk haplotype for DCM (OR 5.90, 95% CI 2.29-15.25, p=0.0001). In conclusion, EDN1 polymorphisms (+138A, A30A, T40I) appear to play a significant role in the pathogenesis of DCM, as they influence the stability of protein. The increased EDN1 production may lead to constriction of coronary arteries, reducing coronary blood flow which may in turn increase the load on left ventricle, impairing contractility of the heart resulting in a DCM phenotype, an end stage of heart failure.