Padmalatha S. Rai

MTHFR gene variants C677T, A1298C and association with Down syndrome: a case-control study from South India.

BACKGROUND: The 5,10-methylenetetrahydrofolate reductase (MTHFR) polymorphisms and low folate levels are associated with inhibition of DNA methyltransferase and consequently DNA hypomethylation. The expanding spectrum of common conditions linked with MTHFR polymorphisms includes certain adverse birth outcome, pregnancy complications, cancers, adult cardiovascular diseases and psychiatric disorders, with several of these associations remaining still controversial. Trisomy 21 or Down syndrome (DS) is the most common genetic cause of mental retardation. It stems predominantly from the failure of chromosome 21 to segregate normally during meiosis. Despite substantial research, the molecular mechanisms underlying non-disjunction leading to trisomy 21 are poorly understood. MATERIALS AND METHODS: Two common variants C677T and A1298C of the MTHFR gene were screened in 36 parents with DS children and 60 healthy couples from Tamil Nadu and Karnataka. The MTHFR genotypes were studied by RFLP analysis of PCR-amplified products and confirmed by sequencing. RESULTS: The CT genotype was seen in three each (8.3%) of case mothers and fathers. One case father showed TT genotype. All the control individuals exhibited the wild type CC genotype. A similar frequency for the uncommon allele C of the second polymorphism was recorded in case mothers (0.35) and fathers (0.37) in comparison with the control mothers (0.39) and fathers (0.37). CONCLUSION: This first report on MTHFR C677T and A1298C polymorphisms in trisomy 21 parents from south Indian population revealed that MTHFR 677CT polymorphism was associated with a risk for Down syndrome.

γ-radiation induces cellular sensitivity and aberrant methylation in human tumor cell lines

Abstract Purpose: Ionizing radiation induces cellular damage through both direct and indirect mechanisms, which may include effects from epigenetic changes. The purpose of this study was to determine the effect of ionizing radiation on DNA methylation patterns that may be associated with altered gene expression. Materials and methods: Sixteen human tumor cell lines originating from various cancers were initially tested for radiation sensitivity by irradiating them with γ-radiation in vitro and subsequently, radiation sensitive and resistant cell lines were treated with different doses of a demethylating agent, 5-Aza-2′-Deoxycytidine (5-aza-dC) and a chromatin modifier, Trichostatin-A (TSA). Survival of these cell lines was measured using 3-(4, 5-Dimethylthiazol- 2-yl)-2, 5-diphenyltetrazolium (MTT) and clonogenic assays. The effect of radiation on global DNA methylation was measured using reverse phase high performance liquid chromatography (RP-HPLC). The transcription response of methylated gene promoters, from cyclin-dependent kinase inhibitor 2A (p16INK4a) and ataxia telangiectasia mutated (ATM) genes, to radiation was measured using a luciferase reporter assay. Results: γ-radiation resistant (SiHa and MDAMB453) and sensitive (SaOS2 and WM115) tumor cell lines were examined for the relationship between radiation sensitivity and DNA methylation. Treatment of cells with 5-aza-dC and TSA prior to irradiation enhanced DNA strand breaks, G2/M phase arrest, apoptosis and cell death. Exposure to γ-radiation led to global demethylation in a time-dependent manner in tumor cells in relation to resistance and sensitivity to radiation with concomitant activation of p16INK4a and ATM gene promoters. Conclusion: These results provide important information on alterations in DNA methylation as one of the determinants of radiation effects, which may be associated with altered gene expression. Our results may help in delineating the mechanisms of radiation resistance in tumor cells, which can influence diagnosis, prognosis and eventually therapy for human cancers.

DNA Barcoding of Authentic and Substitute Samples of Herb of the family Asparagaceae and Asclepiadaceae based on the ITS2 Region

Background: Herbal drugs used to treat illness according to Ayurveda are often misidentified or adulterated with similar plant materials. Objective: To aid taxonomical identification, we used DNA barcoding to evaluate authentic and substitute samples of herb and phylogenetic relationship of four medicinal plants of family Asparagaceace and Asclepiadaceae. Materials and Methods: DNA extracted from dry root samples of two authentic and two substitutes of four specimens belonging to four species were subjected to polymerase chain reaction (PCR) and DNA sequencing. Primers for nuclear DNA (nu ITS2) and plastid DNA (matK and rpoC1) were used for PCR and sequence analysis was performed by Clustal W. The intraspecific variation and interspecific divergence were calculated using MEGA V 4.0. Statistical Analysis: Kimuras two parameter model, neighbor joining and bootstrapping methods were used in this work. Results: The result indicates the efficiency of amplification for ITS2 candidate DNA barcodes was 100% for four species tested. The average interspecific divergence is 0.12 and intraspecific variation was 0.232 in the case of two Asparagaceae species. In two Asclepiadaceae species, average interspecific divergence and intraspecific variation were 0.178 and 0.004 respectively. Conclusions: Our findings show that the ITS2 region can effectively discriminate Asparagus racemosus and Hemidesmus indicus from its substitute samples and hence can resolve species admixtures in raw samples. The ITS2 region may be used as one of the standard DNA barcodes to identify closely related species of family Asclepiadaceae but was noninformative for Asparagaceae species suggesting a need for the development of new markers for each family. More detailed studies involving more species and substitutes are warranted.

Population specific impact of genetic variants in KCNJ11 gene to type 2 diabetes: A case-Control and meta- Analysis study

Background and Objectives Potassium inwardly rectifying channel, subfamily J, member 11 (KCNJ11) gene have a key role in insulin secretion and is of substantial interest as a candidate gene for type 2 diabetes (T2D). The current work was performed to delineate the genetic influence of KCNJ11 polymorphisms on risk of T2D in South Indian population through case-control association study along with systematic review and meta-analysis. Methods A case-control study of 400 T2D cases and controls of South Indian origin were performed to analyze the association of KCNJ11 polymorphisms (rs5219, rs5215, rs41282930, rs1800467) and copy number variations (CNV) on the risk of T2D. In addition a systematic review and meta-analysis for KCNJ11 rs5219 was conducted in 3,831 cases and 3,543 controls from 5 published reports from South-Asian population by searching various databases. Odds ratio with 95% confidence interval (CI) was used to assess the association strength. Cochrans Q, I2 statistics were used to study heterogeneity between the eligible studies. Results KCNJ11 rs5215, C-G-C-C haplotype and two loci analysis (rs5219 vs rs1800467) showed a significant association with T2D but CNV analysis did not show significant variation between T2D cases and control subjects. Lower age of disease onset (P = 0.04) and higher body mass index (BMI) (P = 0.04) were associated with rs5219 TT genotype in T2D patients. The meta-analysis of KCNJ11 rs5219 on South Asian population showed no association on susceptibility to T2D with an overall pooled OR = 0.98, 95% CI = 0.83–1.16. Stratification analysis showed East Asian population and global population were associated with T2D when compared to South Asians. Conclusion KCNJ11 rs5219 is not independently associated with T2D in South-Indian population and our meta-analysis suggests that KCNJ11 polymorphism (rs5219) is associated with risk of T2D in East Asian population and global population but this outcome could not be replicated in South Asian sub groups.

Genetic association of KCNJ10 rs1130183 with seizure susceptibility and computational analysis of deleterious non-synonymous SNPs of KCNJ10 gene

Establishing genetic basis of Idiopathic generalized epilepsies (IGE) is challenging because of their complex inheritance pattern and genetic heterogeneity. Kir4.1 inwardly rectifying channel (KCNJ10) is one of the independent genes reported to be associated with seizure susceptibility. In the current study we have performed a comprehensive in silico analysis of genetic variants in KCNJ10 gene at functional and structural level along with a case-control analysis for the association of rs1130183 (R271C) polymorphism in Indian patients with IGE. Age and sex matched 108 epileptic patients and normal healthy controls were examined. Genotyping of KCNJ10rs1130183 variation was performed using PCR-RFLP method. The risk association was determined by using odds ratio and 95% confidence interval. Functional effects of non-synonymous SNPs (nsSNPs) in KCNJ10 gene were analyzed using SIFT PolyPhen-2, I-Mutant 2.0, PANTHER and FASTSNP. Subsequently, homology modeling of protein three dimensional (3D) structures was performed using Modeller tool (9.10v) and compared the native protein with mutant for assessment of structure and stability. SIFT, PolyPhen-2, I-Mutant 2.0 and PANTHER collectively showed rs1130183, rs1130182 and rs137853073 SNPs inKCNJ10 gene affect protein structure and function. There was a considerable variation in the Root Mean Square Deviation (RMSD) value between the native and mutant structure (1.17Ǻ). Association analysis indicate KCNJ10rs1130183 did not contribute to risk of seizure susceptibility in Indian patients with IGE (OR- 0.38; 95%CI, 0.07-2.05) and T allele frequency (0.02%) was in concordance with dbSNP reports. This study identifies potential SNPs that may contribute to seizure susceptibility and further studies with the selected SNPs in larger number of samples and their functional analysis is required for understanding the variants of KCNJ10 with seizure susceptibility.

Genetic variation in genes involved in folate and drug metabolism in a south indian population

BACKGROUND: Genetic variations represented as single nucleotide polymorphisms (SNPs) vary across the world population. This genetic polymorphism (such as SNPs) plays an important role in pharmacogenomics. SNPs that affects cellular metabolism, by altering the enzyme activity, have an important role in therapeutic outcome. Allele frequencies in number of clinically relevant SNPs within south Indian populations are not yet known. Hence, we genotyped randomly selected unrelated south Indian subjects from different locations of south India representing the heterogeneous ethnic background of the population. MATERIALS AND METHODS: Common variants of MTHFD1, TYMS, SHMT1, MTR, MTRR, CBS and SULT1A1 gene polymorphisms were screened from healthy unrelated south Indian volunteers. Genotypes were determined using RFLP analysis of polymerase chain reaction-amplified products and confirmed by DNA sequencing. Chi-square test was performed to test for deviation from the Hardy-Weinberg equilibrium for each locus. RESULTS: Gene allele frequency for several polymorphisms in our study differed significantly between the populations of other nations reported for several of the SNPs. These results demonstrate that the populations in different geographic regions may have widely varying genetic allele frequencies for clinically relevant SNPs. CONCLUSION: The present study reports, for the first time, the frequency distribution of MTHFD1, TYMS, SHMT1, MTR, MTRR, CBS and SULTIA1 gene polymorphisms in a south Indian population. Population-specific genetic polymorphism studies will help in practicing pharmacogenomic principles in the clinics.

Implications of critical PPARγ2, ADIPOQ and FTO gene polymorphisms in type 2 diabetes and obesity‑mediated susceptibility to type 2 diabetes in an Indian population

Peroxisome proliferator-activated receptors (PPARγ), adiponectin (ADIPOQ) and fat mass and obesity-associated gene (FTO) have been reported as a key candidate genes for obesity, type 2 diabetes (T2D) susceptibility and insulin resistance, and we hypothesize that in the background of obesity, the effect of PPARγ2 (rs1801282), ADIPOQ (rs16861194) and FTO (rs9939609) variant could potentially influence T2D susceptibility. To decipher a more accurate estimation toward its population-specific impact of these variants toward susceptibility to T2D, a case–control study, systematic review and a meta-analysis was performed in a South Asian population. A case–control analysis of 518 T2D cases and 518 controls of Karnataka origin were performed to analyze the association of PPARγ2 (rs1801282), ADIPOQ (rs16861194) and FTO (rs9939609) on the risk of T2D. In addition, a systematic review and meta-analysis for PPARγ2 (rs1801282) and FTO (rs9939609) was elucidated from Asian population. Our investigation showed that PPARγ2 (rs1801282) and FTO (rs9939609) are associated with T2D susceptibility. When T2D cohort was further stratified according to the obesity status, PPARγ2 (rs1801282) and FTO (rs9939609) showed association with T2D only in the obese diabetic group and ADIPOQ (rs16861194) showed no difference in risk of susceptibility to the disease. The meta-analysis of PPARγ2 (rs1801282) showed population-specific association for T2D susceptibility as opposed to FTO (rs9939609) which showed no difference in population effect toward T2D susceptibility. In conclusion, our study showed that PPARγ2 (rs1801282) and FTO (rs9939609) variants are associated with T2D susceptibility when associated with adiposity in Indian population.

GADL1 gene polymorphisms and lithium response in bipolar I disorder: lack of association from an Indian population.

Response to lithium therapy in bipolar I disorder (BD) is known to be heritable, but the precise genetic markers for the same remain to be established. A recent genomewide association study in an East-Asian population identified two single-nucleotide polymorphisms (SNPs) (rs17026688 and rs17026651) in the gene encoding glutamate decarboxylase-like protein 1 (GADL1) to be strongly associated with lithium response (Chen et al., 2014). Despite such a remarkable association, the variant alleles of these SNPs were mainly observed in an Asian population, but were rare or absent in other populations. Further attempts to replicate these findings in independent East-Asian samples did not support the association of GADL1 SNPs with lithium response (Hou et al., 2014; Ikeda et al., 2014). However, no other Asian population has been investigated to date. The SNPs rs17026688 and rs17026651 are located in the introns (introns 6 and 9, respectively) and have no predicted direct functional significance. However, rs17026688 is in high linkage disequilibrium with rs201973599, which is a splice variant affecting the expression of the major isoform of GADL1.

Significance of 5,10-methylenetetrahydrofolate reductase gene variants in acute lymphoblastic leukemia in Indian population: an experimental, computational and meta-analysis

Abstract Acute lymphoblastic leukemia (ALL) arises due to several genetic alterations in progenitor cells, and methotrexate is frequently used as part of the treatment regimen. Although there is evidence for an effect of 5,10-methylenetetrahydrofolate reductase gene (MTHFR) C677T and A1298C variations on drug response in ALL, its risk association for ALL is still unresolved. In a case–control study of 203 patients with ALL and 246 controls and meta-analysis in the Indian population, we showed an insignificant association of MTHFR C677T and A1298C genotypes with childhood and adult ALL. Comprehensive in silico characterization of non-synonymous single nucleotide polymorphisms (nsSNPs) and SNPs of the 3′ untranslated region (UTR) revealed nine nsSNPs as deleterious, and three SNPs in the 3′UTR could possibly alter the binding of miRNAs. The study revealed that several overlooked SNPs may contribute to the risk of ALL susceptibility and further studies of these SNPs with functional characterization in a large sample size are required to understand the significant role of MTHFR in ALL development.

Intraindividual somatic variations in MTHFR gene polymorphisms in relation to colon cancer

AIM MTHFR mediates the one carbon metabolism pathway. Two common genetic variants, C677T and A1298C, of MTHFR are associated with number of human diseases, including cancer, as well as being involved in the modulation of therapy outcome to antifolate drugs. To understand the distribution pattern of SNPs among different tissues of an individual, we examined MTHFR polymorphisms in normal and colon cancer tissues and compared the genotype frequencies in peripheral blood samples. MATERIALS & METHODS DNA was isolated from tumor tissue and matched normal tissues from 155 colon cancer patients. These samples as well as DNA from blood samples of the control group (n = 294) were analyzed for MTHFR polymorphisms by PCR-RFLP and confirmed by a direct DNA sequencing method. RESULTS Our data suggest that the allele and genotype frequencies of C677T and A1298C were significantly different between tumor tissues and both types of normal tissues. We have established that MTHFR variants that exist in tumor and matched normal tissues of colon cancer patients differ suggesting somatic variation in MTHFR polymorphisms among different tissues of an individual. The MTHFR A1298C polymorphism was associated with risk of colon cancer. CONCLUSION Different MTHFR variants may exist in different tissues to maintain physiological functions and may have implications for disease susceptibility and pharmacogenomics based therapies. Original submitted 21 January 2013; Revision submitted 3 January 2014.