Sanjiban Chakrabarty

DNA methylation analysis of phenotype specific stratified Indian population

BackgroundDNA methylation and its perturbations are an established attribute to a wide spectrum of phenotypic variations and disease conditions. Indian traditional system practices personalized medicine through indigenous concept of distinctly descriptive physiological, psychological and anatomical features known as prakriti. Here we attempted to establish DNA methylation differences in these three prakriti phenotypes.MethodsFollowing structured and objective measurement of 3416 subjects, whole blood DNA of 147 healthy male individuals belonging to defined prakriti (Vata, Pitta and Kapha) between the age group of 20-30years were subjected to methylated DNA immunoprecipitation (MeDIP) and microarray analysis. After data analysis, prakriti specific signatures were validated through bisulfite DNA sequencing.ResultsDifferentially methylated regions in CpG islands and shores were significantly enriched in promoters/UTRs and gene body regions. Phenotypes characterized by higher metabolism (Pitta prakriti) in individuals showed distinct promoter (34) and gene body methylation (204), followed by Vata prakriti which correlates to motion showed DNA methylation in 52 promoters and 139 CpG islands and finally individuals with structural attributes (Kapha prakriti) with 23 and 19 promoters and CpG islands respectively. Bisulfite DNA sequencing of prakriti specific multiple CpG sites in promoters and 5′-UTR such as; LHX1 (Vata prakriti), SOX11 (Pitta prakriti) and CDH22 (Kapha prakriti) were validated. Kapha prakriti specific CDH22 5′-UTR CpG methylation was also found to be associated with higher body mass index (BMI).ConclusionDifferential DNA methylation signatures in three distinct prakriti phenotypes demonstrate the epigenetic basis of Indian traditional human classification which may have relevance to personalized medicine.

Copy number variations are progressively associated with the pathogenesis of colorectal cancer in ulcerative colitis.

AIM To evaluate the association of known copy number variations (CNVs) in ulcerative colitis (UC) progressing to colorectal cancer. METHODS Microsatellite instability analysis using the National Cancer Institutes panel of markers, and CNV association studies using Agilent 2 × 105 k arrays were done in tissue samples from four patient groups with UC: those at low risk (LR) or high risk of developing colorectal cancer, those with premalignant dysplastic lesions, and those with colitis-associated colorectal cancer (CAC). DNA from tissue samples of these groups were independently hybridized on arrays and analyzed. The data obtained were further subjected to downstream bioinformatics enrichment analysis to examine the correlation with CAC progression. RESULTS Microarray analysis highlighted a progressive increase in the total number of CNVs [LR (n = 178) vs CAC (n = 958), 5.3-fold], gains and losses [LR (n = 37 and 141) vs CAC (n = 495 and 463), 13.4- and 3.3-fold, respectively], size [LR (964.2 kb) vs CAC (10540 kb), 10.9-fold] and the number of genes in such regions [LR (n = 119) vs CAC (n = 455), 3.8-fold]. Chromosome-wise analysis of CNVs also showed an increase in the number of CNVs across each chromosome. There were 38 genes common to all four groups in the study; 13 of these were common to cancer genes from the Genetic Disease Association dataset. The gene set enrichment analysis and ontology analysis highlighted many cancer-associated genes. All the samples in the different groups were microsatellite stable. CONCLUSION Increasing numbers of CNVs are associated with the progression of UC to CAC, and warrant further detailed exploration.

Upregulation of TFAM and mitochondria copy number in human lymphoblastoid cells

Mitochondria are central to several physiological and pathological conditions in humans. In the present study, we performed copy number analysis of nuclear encoded mitochondrial genes, in peripheral blood mononuclear cells (PBMCs) and its representative lymphoblastoid cells (LCLs). We have observed hyper diploid copies of mitochondrial transcription factor A (TFAM) gene in the LCLs along with increased mtDNA copy number, mitochondrial mass, intracellular ROS and mitochondrial membrane potential, suggesting elevated mitochondrial biogenesis in LCLs. Gene expression analysis confirmed TFAM over-expression in LCLs when compared to PBMC. Based on our observation, we suggest that increased copy number of TFAM gene upregulates its expression, increases mtDNA copy numbers and protects it from oxidative stress induced damage in the transformed LCLs.

Aberrant gene-specific DNA methylation signature analysis in cervical cancer

Multicomponent molecular modifications such as DNA methylation may offer sensitive and specific cervical intraepithelial neoplasia and cervical cancer biomarkers. In this study, we tested cervical tissues at various stages of tumor progression for 5-methylcytosine and 5-hydroxymethylcytosine levels and also DNA promoter methylation profile of a panel of genes for its diagnostic potential. In total, 5-methylcytosine, 5-hydroxymethylcytosine, and promoter methylation of 33 genes were evaluated by reversed-phase high-performance liquid chromatography, enzyme-linked immunosorbent assay based technique, and bisulfate-based next generation sequencing. The 5-methylcytosine and 5-hydroxymethylcytosine contents were significantly reduced in squamous cell carcinoma and receiver operating characteristic curve analysis showed a significant difference in (1) 5-methylcytosine between normal and squamous cell carcinoma tissues (area under the curve = 0.946) and (2) 5-hydroxymethylcytosine levels among normal, squamous intraepithelial lesions and squamous cell carcinoma. Analyses of our next generation sequencing results and data from five independent published studies consisting of 191 normal, 10 low-grade squamous intraepithelial lesions, 21 high-grade squamous intraepithelial lesions, and 335 malignant tissues identified a panel of nine genes (ARHGAP6, DAPK1, HAND2, NKX2-2, NNAT, PCDH10, PROX1, PITX2, and RAB6C) which could effectively discriminate among the various groups with sensitivity and specificity of 80%–100% (p < 0.05). Furthermore, 12 gene promoters (ARHGAP6, HAND2, LHX9, HEY2, NKX2-2, PCDH10, PITX2, PROX1, TBX3, IKBKG, RAB6C, and DAPK1) were also methylated in one or more of the cervical cancer cell lines tested. The global and gene-specific methylation of the panel of genes identified in our study may serve as useful biomarkers for the early detection and clinical management of cervical cancer.

Comprehensive DNA copy number profile and BAC library construction of an Indian individual

Bacterial artificial chromosomes (BACs) are used in genomic variation studies due to their capacity to carry a large insert, their high clonal stability, low rate of chimerism and ease of manipulation. In the present study, an attempt was made to create the first genomic BAC library of an anonymous Indian male (IMBL4) consisting of 100,224 clones covering the human genome more than three times. Restriction mapping of 255 BAC clones by pulse field gel electrophoresis confirmed an average insert size of 120 kb. The library was screened by PCR using SHANK3 (SH3 and multiple ankyrin repeat domains 3) and OLFM3 (olfactomedin 3) specific primers. A selection of clones was analyzed by fluorescent in situ hybridization (FISH) and sequencing. Fine mapping of copy number variable regions by array based comparative genomic hybridization identified 467 CNVRs in the IMBL4 genome. The IMBL4 BAC library represents the first cataloged Indian genome resource for applications in basic and clinical research.

Perspectives on Translational Genomics and Public Health in India

It is now recognized worldwide that anticipation and prevention of diseases have significant advantages for the health and healthy ageing of the population. Early recognition of the disease in a vulnerable population such as in children aged <5 years and adults aged >60 years enhances our preparedness for any eventualities and future burden of the diseases to society. It is also recognized that current public health practices alone cannot bring about the desired outcome. When tackling public health-related issues, such problems must be recognized and state-of-the-art principles and innovations from genomic sciences, information technologies, and medical specialties must be encompassed and embraced. These will enhance strategies for preparedness and provide us with a better understanding of how to identify, manage, and control disease burdens. The ever expanding landscape of genomics research also includes experimental and computational approaches for effectively utilizing DNA sequence information. From these perspectives, the intricacies of Mendelian single gene disorders are the least challenging compared to intricacies of multi-dimensional host factors for infectious diseases or complex disorders such as cancer. The concepts of public health in India are on firm footing; however, integration of contemporary advances to implement public health principles into practice has neither been attempted nor impacted on disease burden or our preparedness to prevent eventualities. At the same time, translational genomics is gradually paving the way for personalized medicine. Principles of personalized medicine remain to be fully understood and practiced despite the pharmacogenomics-based future of drug development, and treatment has not been as exciting as the advances in genomics we are witnessing today. The relevance, importance, and translational impediments of these advances will be discussed.

DNA methylation detection at single base resolution using targeted next generation bisulfite sequencing and cross validation using capillary sequencing.

With a purpose of accurate and simultaneous determination of DNA methylation from multiple loci in multiple samples, here, we are demonstrating a method to aid rapid DNA methylation detection of genomic sequences. Using genomic DNA of peripheral blood from 14 healthy individuals, DNA methylation in 465 CpG sites from 12 loci of genes (ADAM22, ATF2, BCR, CD83, CREBBP, IL12B, IL17RA, MAP2K2, RBM38, TGFBR2, TGFBR3, and WNT5A) was analysed by targeted next generation bisulfite sequencing. Analysed region for three genes, BCR, IL17RA and RBM38 showed an absolute mean DNA methylation of 25.6%, 89.2% and 38.9% respectively. Other nine gene loci were unmethylated and exhibited <10% absolute mean DNA methylation. Two genes, IL17RA and RBM38 were technically validated using direct capillary sequencing and results were comparable with positive correlation (P=0.0088 & P<0.0001 respectively) in the CpG sites for DNA methylation. All CpG sites analysed from RBM38 genes locus displayed 95% limits of agreement for DNA methylation measurements from the two methods. The present approach provides a fast and reliable DNA methylation quantitative data at single base resolution with good coverage of the CpG sites under analysis in multiple loci and samples simultaneously. Use of targeted next generation bisulfite sequencing may provide an opportunity to explore genes in the discovery panel for biomarker identification and facilitate functional validation.

Genotypic detection of fluoroquinolone resistance in drug-resistant Mycobacterium tuberculosis at a tertiary care centre in south Coastal Karnataka, India

OBJECTIVES This study aimed to characterise mutations associated with fluoroquinolone resistance in drug-resistant Mycobacterium tuberculosis clinical isolates at a tertiary care centre in south Coastal Karnataka, India. METHODS DNA from 50 M. tuberculosis clinical isolates was extracted and the gyrA and gyrB genes were amplified. Purified amplicons of gyrA and gyrB were sequenced and extended-sequencing PCR products were analysed. Analysis of mutations in gyrA and gyrB was done using the MUBII-TB-DB database. Statistical analysis was performed using SPSS v.22 and data were compared by χ2 test. A P-value of <0.05 was considered statistically significant. RESULTS Mutations conferring resistance to fluoroquinolones were observed in 9 isolates (18%). The gyrA A281G (D94G) mutation was observed in 3 isolates (6%), whereas mutations G280T (D94Y) and A281C (D94A) were each observed in 1 isolate (2%). Mutation G1498A (D500N) in gyrB alone was observed in 2 isolates (4%). Two isolates (4%) had mutations both in gyrA and gyrB; gyrA mutation T271C (S91P) was observed in one isolate, whereas the other isolate had gyrA C269G (A90G), but both isolates had a common G1498A (D500N) gyrB mutation. G284C mutation conferring S95T polymorphism (not associated with fluoroquinolone resistance) was observed in 39/50 isolates (78%). CONCLUSION gyrA mutations at codons 94, 91 and 90 and gyrB mutation G1498A (D500N) were the most common mutations associated with fluoroquinolone resistance in clinical isolates in this study. Future studies including a larger number of samples are desirable to fully explore the true extent of fluoroquinolone resistance and mutations associated with them.

Clustered miRNAs and their role in biological functions and diseases: Biological regulation by miRNA clusters

MicroRNAs (miRNAs) are endogenous, small non‐coding RNAs known to regulate expression of protein‐coding genes. A large proportion of miRNAs are highly conserved, localized as clusters in the genome, transcribed together from physically adjacent miRNAs and show similar expression profiles. Since a single miRNA can target multiple genes and miRNA clusters contain multiple miRNAs, it is important to understand their regulation, effects and various biological functions. Like protein‐coding genes, miRNA clusters are also regulated by genetic and epigenetic events. These clusters can potentially regulate every aspect of cellular function including growth, proliferation, differentiation, development, metabolism, infection, immunity, cell death, organellar biogenesis, messenger signalling, DNA repair and self‐renewal, among others. Dysregulation of miRNA clusters leading to altered biological functions is key to the pathogenesis of many diseases including carcinogenesis. Here, we review recent advances in miRNA cluster research and discuss their regulation and biological functions in pathological conditions.

Epigenomics, Pharmacoepigenomics, and Personalized Medicine in Cervical Cancer

Epigenomics encompasses the study of genome-wide changes in DNA methylation, histone modifications and noncoding RNAs leading to altered transcription, chromatin structure, and posttranscription RNA processing, respectively, resulting in an altered rate of gene expression. The role of epigenetic modifications facilitating human diseases is well established. Previous studies have identified histone and cytosine code during normal and pathological conditions with special emphasis on how these modifications regulate transcriptional events. Recent studies have also mapped these epigenetic modification and pathways leading to carcinogenesis. Discovery of drugs that target proteins/enzymes in the epigenetic pathways may provide better therapeutic opportunities, and identification of such modulators for DNA methylation, histone modifications, and expression of noncoding RNAs for several cancer types is underway. In this review, we provide a detailed description of recent developments in the field of epigenetics and its impact on personalized medicine to manage cervical cancer.