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Background and AimsA link between gut microbiota and Ulcerative colitis (UC) has been established in several studies. However, only a few studies have examined specific changes in microbiota associated with different phases of disease activity in UC. In this study, we attempted to identify differentially abundant taxa between (i) UC patients and healthy controls and (ii) different phases of disease activity, in a genetically distinct north Indian (NI) population.Methods16S rRNA (V3–V4) sequencing of 105 patients with UC [newly diagnosed (n=14); patients in remission (n=36) and active disease (relapse, n=55)]; and 36 healthy controls was performed and analysed.ResultsLower gut microbial diversity; enrichment of lactate-producing bacteria namely Streptococcus, Bifidobacterium and Lactobacillus; and depletion of butyrate-producing bacteria (e.g., Lachnospiraceae and Ruminococcaceae), were observed among UC patients. Subgroup analysis revealed differential abundance of Escherichia-Shigella, Streptococcus, Enterococcus and Faecalibacterium in newly diagnosed UC patients. No discrete microbial features were observed between patients in remission and those with active disease. Co-occurrence network analysis revealed a mutualistic association between opportunistic pathogens and Bifidobacterium and Lactobacillus and antagonistic relationship with butyrate-producers.ConclusionThis first faecal microbiome study among NI UC cohort elucidated dysanaerobiosis; loss of short chain fatty acid producers and enrichment of inflammation associated microbes; population specific differential microbial genera; and a potential microbial signature for early dysbiosis.

Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gut. Genetic association studies have identified the highly variable human leukocyte antigen (HLA) region as the strongest susceptibility locus for IBD and specifically DRB1*01:03 as a determining factor for ulcerative colitis (UC). However, for most of the association signal such as delineation could not be made because of tight structures of linkage disequilibrium within the HLA. The aim of this study was therefore to further characterize the HLA signal using a transethnic approach. We performed a comprehensive fine mapping of single HLA alleles in UC in a cohort of 9272 individuals with African American, East Asian, Puerto Rican, Indian and Iranian descent and 40 691 previously analyzed Caucasians, additionally analyzing whole HLA haplotypes. We computationally characterized the binding of associated HLA alleles to human self-peptides and analyzed the physicochemical properties of the HLA proteins and predicted self-peptidomes. Highlighting alleles of the HLA-DRB1*15 group and their correlated HLA-DQ-DR haplotypes, we not only identified consistent associations (regarding effects directions/magnitudes) across different ethnicities but also identified population-specific signals (regarding differences in allele frequencies). We observed that DRB1*01:03 is mostly present in individuals of Western European descent and hardly present in non-Caucasian individuals. We found peptides predicted to bind to risk HLA alleles to be rich in positively charged amino acids. We conclude that the HLA plays an important role for UC susceptibility across different ethnicities. This research further implicates specific features of peptides that are predicted to bind risk and protective HLA proteins.

Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gut. Genetic association studies have identified the highly variable human leukocyte antigen (HLA) region as the strongest susceptibility locus for IBD, and specifically DRB1*01:03 as a determining factor for ulcerative colitis (UC). However, for most of the association signal such a delineation could not be made due to tight structures of linkage disequilibrium within the HLA. The aim of this study was therefore to further characterize the HLA signal using a trans-ethnic approach. We performed a comprehensive fine mapping of single HLA alleles in UC in a cohort of 9,272 individuals with African American, East Asian, Puerto Rican, Indian and Iranian descent and 40,691 previously analyzed Caucasians, additionally analyzing whole HLA haplotypes. We computationally characterized the binding of associated HLA alleles to human self-peptides and analysed the physico-chemical properties of the HLA proteins and predicted self-peptidomes. Highlighting alleles of the HLA-DRB1*15 group and their correlated HLA-DQ-DR haplotypes, we identified consistent associations across different ethnicities but also identified population-specific signals. We observed that DRB1*01:03 is mostly present in individuals of Western European descent and hardly present in non-Caucasian individuals. We found peptides predicted to bind to risk HLA alleles to be rich in positively charged amino acids such. We conclude that the HLA plays an important role for UC susceptibility across different ethnicities. This research further implicates specific features of peptides that are predicted to bind risk and protective HLA proteins.

The first ever genome-wide association study (GWAS) of ulcerative colitis in genetically distinct north Indian population identified two novel genes namely CFB and SLC44A4. Considering their biological relevance, we investigated allelic/genetic heterogeneity in these genes among ulcerative colitis cohorts of north Indian, Japanese and Dutch origin using high-density ImmunoChip case–control genotype data. Comparative linkage disequilibrium profiling and test of association were performed. Of the 28 CFB SNPs, similar strength of association was observed for rs4151657 (novel ulcerative colitis GWAS SNP) in north Indians (P=1.73 × 10−10) and Japanese (P=2.02 × 10−12) but not in the Dutch. Further, a three-marker haplotype was shared between north Indians and Japanese (P

Ulcerative colitis (UC), one of the two clinical subtypes of inflammatory bowel disease is perceived as a potential ‘sleeping giant’ in the Indian subcontinent. Clinical manifestation is overall believed to be the same across ethnic groups but overwhelming genetics from large European and fewer non-European studies have revealed shared as well as unique disease susceptibly signatures between them, pointing to population specific differences at genomic and environmental levels. A systematic recount of the four major eras in UC genetics spanning earliest linkage analysis, cherry picked candidate gene association studies, unbiased genomewide association studies, their logical extension in trans-ethnic setting (Immunochip study), lastly whole exome sequencing efforts for rare variant burden; and lessons learnt thereof in context of genetically distinct Indian population was attempted in this review. Genetic heterogeneity manifesting at allelic/locus level across these approaches has been the consistent finding through the range of pan India studies. On the other hand, these salient findings also highlight the limitations of even the best of these genetic leads for prognostic/clinical application. The imminent need, therefore, for the UC research community to adopt newer approaches/tools with improved study design to (i) gain better insight into genetic/mechanistic basis of disease; (ii) identify biomarkers of immediate translational value; and (iii) develop new/alternate therapeutic options is emphasized at the end.

Objective Over 100 ulcerative colitis (UC) loci have been identified by genome-wide association studies (GWASs) primarily in Caucasians (CEUs). Many of them have weak effects on disease susceptibility, and the bulk of the heritability cannot be ascribed to these loci. Very little is known about the genetic background of UC in non-CEU groups. Here we report the first GWAS on UC in a genetically distinct north Indian (NI) population.Design A genome-wide scan was performed on 700 cases and 761 controls. 18 single-nucleotide polymorphisms (SNPs) (pResults Seven novel human leucocyte antigen (HLA)-independent SNPs from chromosome 6, located in 3.8-1, BAT2, MSH5, HSPA1L, SLC44A4, CFB and NOTCH4, exceeded pConclusions This study shows varying contribution of the HLA region to UC in different populations. Different environmental exposures and the characteristic genetic structure of the HLA locus across ethnic groups collectively make it amenable to the discovery of causative alleles by transethnic resequencing. This may lead to an improved understanding of the molecular mechanisms underlying UC.

Indian demographic history includes special features such as founder effects, interpopulation segregation, complex social structure with a caste system and elevated frequency of consanguineous marriages. It also presents a higher frequency for some rare mendelian disorders and in the last two decades increased prevalence of some complex disorders. Despite the fact that India represents about one-sixth of the human population, deep genetic studies from this terrain have been scarce. In this study, we analyzed high-density genotyping and whole-exome sequencing data of a North and a South Indian population. Indian populations show higher differentiation levels than those reported between populations of other continents. In this work, we have analyzed its consequences, by specifically assessing the transferability of genetic markers from or to Indian populations. We show that there is limited genetic marker portability from available genetic resources such as HapMap or the 1,000 Genomes Project to Indian populations, which also present an excess of private rare variants. Conversely, tagSNPs show a high level of portability between the two Indian populations, in contrast to the common belief that North and South Indian populations are genetically very different. By estimating kinship from mates and consanguinity in our data from trios, we also describe different patterns of assortative mating and inbreeding in the two populations, in agreement with distinct mating preferences and social structures. In addition, this analysis has allowed us to describe genomic regions under recent adaptive selection, indicating differential adaptive histories for North and South Indian populations. Our findings highlight the importance of considering demography for design and analysis of genetic studies, as well as the need for extending human genetic variation catalogs to new populations and particularly to those with particular demographic histories., International fellowship funded by Center for Neurogenomics and Cognitive Research (CNCR), VU, Amsterdam, The Netherlands to GJ; Research grant from J C Bose fellowship to BKT; grant # BT/01/COE/07/UDSC to BKT and salary support to GJ are gratefully acknowledged. FC was supported by a Beatriu de Pinós (2010-BP- B-00128) fellowship and MM by a PhD grant both from AGAUR (Generalitat de Catalunya). Funding to FC by grant SAF2012-35025 from the Ministerio de Economía y Competitividad (Spain); Funding to JB by grants BFU2010-19443 from the Ministerio de Ciencia y Tecnología (Spain), PRI-PIBIN-2011-0942 from the Ministerio de Economía y Competitividad (Spain), and from the Direcció General de Recerca, Generalitat de Catalunya (Grup de Recerca Consolidat 2009 SGR 1101).

Objective Genome-wide association studies (GWAS) and their subsequent meta-analyses have changed the landscape of genetics in rheumatoid arthritis (RA) by uncovering several novel genes. Such studies are heavily weighted by samples from Caucasian populations, but they explain only a small proportion of total heritability. Our previous studies in genetically distinct North Indian RA cohorts have demonstrated apparent allelic/genetic heterogeneity between North Indian and Western populations, warranting GWAS in non-European populations. We undertook this study to detect additional disease-associated loci that may be collectively important in the presence or absence of genes with a major effect. Methods High-quality genotypes for >600,000 single-nucleotide polymorphisms (SNPs) in 706 RA patients and 761 controls from North India were generated in the discovery stage. Twelve SNPs showing suggestive association (P < 5 × 10−5) were then tested in an independent cohort of 927 RA patients and 1,148 controls. Additional disease-associated loci were determined using support vector machine (SVM) analyses. Fine-mapping of novel loci was performed by using imputation. Results In addition to the expected association of the HLA locus with RA, we identified association with a novel intronic SNP of ARL15 (rs255758) on chromosome 5 (Pcombined = 6.57 × 10−6; odds ratio 1.42). Genotype–phenotype correlation by assaying adiponectin levels demonstrated the functional significance of this novel gene in disease pathogenesis. SVM analysis confirmed this association along with that of a few more replication stage genes. Conclusion In this first GWAS of RA among North Indians, ARL15 emerged as a novel genetic risk factor in addition to the classic HLA locus, which suggests that population-specific genetic loci as well as those shared between Asian and European populations contribute to RA etiology. Furthermore, our study reveals the potential of machine learning methods in unraveling gene–gene interactions using GWAS data.

OBJECTIVES There are suggestions that the MDR1 (ABCB1) gene is associated with ulcerative colitis (UC) in Caucasians. We investigated whether common MDR1 variants were associated with UC in the genetically heterogeneous North Indian population. METHODS Confirmed cases of UC and healthy controls frequency matched for age (+/-10 years) and geographic region were studied. Three exonic (C1236T, G2677T/A, and C3435T) and one promoter (C129T) single nucleotide polymorphism (SNP) in the gene were assessed. Allelic, genotypic, and haplotypic associations were evaluated. RESULTS A total of 270 patients and 274 controls were studied. The mean age at diagnosis (+/-SD) of the patients was 38.6 (+/-12.4) years. Most patients had left-sided disease (63.3%) and steroids were administered to them (78%). All SNPs were in Hardy-Weinberg equilibrium in the controls. SNP C129T was monomorphic in the population. SNP C1236T was significantly (P=0.05) overrepresented in the UC patients. Borderline nonsignificant associations were also evident with SNP G2677A/T. Three-marker (C1236T, G2677T/A, C3435T) and two-marker (C1236T, G2677T/A) haplotype analysis revealed significant associations with UC (TTT, P=0.04; TGT, P=0.01; TT, P=0.01; CT, P=0.03). There were indications that SNPs C1236T and G2677T/A were significantly associated with earlier age of onset (

Genome-wide association studies (GWAS) and their subsequent meta-analyses have changed the landscape of genetics in rheumatoid arthritis (RA) by uncovering several novel genes. Such studies are heavily weighted by samples from Caucasian populations, but they explain only a small proportion of total heritability. Our previous studies in genetically distinct North Indian RA cohorts have demonstrated apparent allelic/genetic heterogeneity between North Indian and Western populations, warranting GWAS in non-European populations. We undertook this study to detect additional disease-associated loci that may be collectively important in the presence or absence of genes with a major effect.High-quality genotypes for600,000 single-nucleotide polymorphisms (SNPs) in 706 RA patients and 761 controls from North India were generated in the discovery stage. Twelve SNPs showing suggestive association (P5 × 10(-5)) were then tested in an independent cohort of 927 RA patients and 1,148 controls. Additional disease-associated loci were determined using support vector machine (SVM) analyses. Fine-mapping of novel loci was performed by using imputation.In addition to the expected association of the HLA locus with RA, we identified association with a novel intronic SNP of ARL15 (rs255758) on chromosome 5 (Pcombined = 6.57 × 10(-6); odds ratio 1.42). Genotype-phenotype correlation by assaying adiponectin levels demonstrated the functional significance of this novel gene in disease pathogenesis. SVM analysis confirmed this association along with that of a few more replication stage genes.In this first GWAS of RA among North Indians, ARL15 emerged as a novel genetic risk factor in addition to the classic HLA locus, which suggests that population-specific genetic loci as well as those shared between Asian and European populations contribute to RA etiology. Furthermore, our study reveals the potential of machine learning methods in unraveling gene-gene interactions using GWAS data.

Genome-Wide Association studies (GWAS) of both Crohn's Disease (CD) and Ulcerative Colitis (UC) have unearthed over 40 risk conferring variants. Recently, a meta-analysis on UC revealed several loci, most of which were either previously associated with UC or CD susceptibility in populations of European origin. In this study, we attempted to replicate these findings in an ethnically distinct north Indian UC cohort. 648 UC cases and 850 controls were genotyped using Infinium Human 660W-quad. Out of 59 meta-analysis index SNPs, six were not in the SNP array used in the study. Of the remaining 53 SNPs, four were found monomorphic. Association (p

Background Previous studies have attempted to link hygiene hypothesis with IBD. However most of these studies come from developed countries where the level of hygiene is high and universal. Very little data is available from developing countries. The present study explores the truth of hygiene hypotheses and other risk factors for ulcerative colitis (UC) in a North Indian population where the prevalence of UC has been increasing. Methods A total of 518 patients diagnosed with UC and 188 age-matched controls were included in the study. A structured questionnaire concerning socio-demographics and level of hygiene was completed by all participants. Logistic regression analysis was used to study the association between hygiene-related factors and the risk for UC. Odds ratios and 95% confidence intervals were estimated. Results There was a higher proportion of females (P