Inflammatory Bowel Disease Risk Loci Research Articles

Many Inflammatory Bowel Disease Risk Loci Include Regions That Regulate Gene Expression in Immune Cells and the Intestinal Epithelium

The contribution of genetic factors to the pathogenesis of inflammatory bowel disease (IBD) has been established by twin, targeted-sequencing, and genome-wide association studies. These studies identified many risk loci, and research is underway to identify causal variants. These studies have focused mainly on protein-coding genes. We investigated other functional elements in the human genome, such as regulatory regions. Using acetylated histone 3 lysine 27 chromatin immunoprecipitation and sequencing, we identified tens of thousands of potential regulatory regions that are active in intestinal epithelium (primary intestinal crypts and cultured organoids) isolated from resected material and from biopsies collected during ileo-colonoscopies and immune cells (monocytes, macrophages, CD34(+), CD4(+), and CD8(+)). We correlated these regions with susceptibility loci for IBD. We have generated acetylated histone 3 lysine 27 profiles from primary intestinal epithelium and cultured organoids, which we have made publically available. We found that 45 of 163 single nucleotide polymorphisms (SNPs) associated with IBD overlap specifically with active regulatory elements. In addition, by taking strong linkage disequilibrium into account, another 47 IBD-associated SNPs colocalized with active regulatory elements through other SNPs in their vicinity. Altogether, 92 of 163 IBD-associated SNPs correlated with distinct active regulatory elements-a frequency 2.5- to 3.5-fold greater than that expected from random sampling. The variations in these SNPs often create or disrupt known binding motifs; they might affect the binding of transcriptional regulators to alter expression of regulated genes. In addition to variants in protein coding genes, variants in noncoding DNA regulatory regions that are active in intestinal epithelium and immune cells are potentially involved in the pathogenesis of IBD.

Replication Study of Ulcerative Colitis Risk Loci in a Lithuanian–Latvian Case–Control Sample

Differences between populations might be reflected in their different genetic risk maps to complex diseases, for example, inflammatory bowel disease. We here investigated the role of known inflammatory bowel disease-associated single nucleotide polymorphisms (SNPs) in a subset of patients with ulcerative colitis (UC) from the Northeastern European countries Lithuania and Latvia and evaluated possible epistatic interactions between these genetic variants. We investigated 77 SNPs derived from 5 previously published genome-wide association studies for Crohn's disease and UC. Our study panel comprised 444 Lithuanian and Latvian patients with UC and 1154 healthy controls. Single marker case-control association and SNP-SNP epistasis analyses were performed. We found 14 SNPs tagging 9 loci, including 21q21.1, NKX2-3, MST1, the HLA region, 1p36.13, IL10, JAK2, ORMDL3, and IL23R, to be associated with UC. Interestingly, the association of UC with previously identified variants in the HLA region was not the strongest association in our study (P = 4.34 × 10, odds ratio [OR] = 1.25), which is in contrast to all previously published studies. No association with any disease subphenotype was found. SNP-SNP interaction analysis showed significant epistasis between SNPs in the PTPN22 (rs2476601) and C13orf31 (rs3764147) genes and increased risk for UC (P = 1.64 × 10, OR = 2.44). The association has been confirmed in the Danish study group (P = 0.04, OR = 3.25). We confirmed the association of the 9 loci (21q21.1, 1p36.13, NKX2-3, MST1, the HLA region, IL10, JAK2, ORMDL3, and IL23R) with UC in the Lithuanian-Latvian population. SNP-SNP interaction analyses showed that the combination of SNPs in the PTPN22 (rs2476601) and C13orf31 (rs3764147) genes increase the risk for UC.

Genetic risk factors forClostridium difficileinfection in ulcerative colitis

Patients with inflammatory bowel disease (IBD) are at higher risk for Clostridium difficile infection (CDI). Disruption of gut microbiome and interaction with the intestinal immune system are essential mechanisms for pathogenesis of both CDI and IBD. Whether genetic polymorphisms associated with susceptibility to IBD are also associated with risk of CDI is unknown. To use a well-characterised and genotyped cohort of patients with UC to (i) identify clinical risk factors for CDI; (ii) examine if any of the IBD genetic risk loci were associated with CDI; and (iii) to compare the performance of predictive models using clinical and genetic risk factors in determining risk of CDI. We used a prospective registry of patients from a tertiary referral hospital. Medical record review was performed to identify all ulcerative colitis (UC) patients within the registry with a history of CDI. All patients were genotyped on the Immunochip. We examined the association between the 163 risk loci for IBD and risk of CDI using a dominant genetic model. Model performance was examined using receiver operating characteristics curves. The study included 319 patients of whom 29 developed CDI (9%). Female gender and pancolitis were associated with increased risk, while use of anti-TNF was protective against CDI. Six genetic polymorphisms including those at TNFRSF14 [Odds ratio (OR) 6.0, P-value 0.01] were associated with increased risk while 2 loci were inversely associated. On multivariate analysis, none of the clinical parameters retained significance after adjusting for genetics. Presence of at least one high-risk locus was associated with an increase in risk for CDI (20% vs. 1%) (P = 6 × 10⁻⁹). Compared to 11% for a clinical model, the genetic loci explained 28% of the variance in CDI risk and had a greater AUROC. Host genetics may influence susceptibility to Clostridium difficile infection in patients with ulcerative colitis.

P685 Ulcerative colitis risk loci in Lithuanian-Latvian case control sample – a replication study

P685 Ulcerative colitis risk loci in Lithuanian-Latvian case control sample – a replication study

Erratum: Corrigendum: Meta-analysis identifies 29 additional ulcerative colitis risk loci, increasing the number of confirmed associations to 47

Nat. Genet. 43, 246–252 (2011); published online 6 February 2011; corrected after print 11 August 2011 In the version of this article initially published, an affiliation was missing for two authors, Maria Gazouli and Nicholas P. Anagnou. They are also affiliated with the Foundation for Biomedical Research of the Academy of Athens in Athens, Greece.

Haplotype-based analysis of ulcerative colitis risk loci identifies both IL2 and IL21 as susceptibility genes in Han Chinese

The incidence of ulcerative colitis (UC) varies between Western and Eastern ethnicities. A distinct genetic background may play a role in the differences. Until now, very little was known of the UC genetics in Asian populations. Here we performed a haplotype-based analysis of six known UC susceptibility loci in Han Chinese patients. In all, 245 UC patients and 300 healthy controls of Han Chinese descent were genotyped for 27 single nucleotide polymorphisms (SNPs), which cover the major haplotypes of the chromosome regions containing IL10, IL2/IL21, MYO9B, ECM1, MST1, and IL23R in Han Chinese. In contrast to the tight linkage disequilibrium (LD) block of the IL2/IL21 region in Caucasians, IL2 and IL21 reside in two independent LD blocks in Han Chinese. The IL2 SNP rs2069762 (P = 7.0 × 10(-4) , odds ratio [OR] = 1.54, 95% confidence interval [CI] 1.20-1.99) and the IL21 SNP rs2055979 (P = 1.2 × 10(-4) , OR = 1.50, 95% CI 1.17-1.92) were independently associated with UC. We identified one risk haplotype in IL2 and another independent risk haplotype in IL21. In addition to the IL2/IL21 locus, we observed association of the TT genotype of SNP rs1545620 in MYO9B with UC (P = 0.0169; OR = 0.29, 95% CI 0.11-0.78) and association of rs17375018 in IL23R with pancolitis in Chinese UC patients (P = 0.002; OR = 2.38, 95% CI 1.41-4.02). Our study confirmed the association of the IL2/IL21 region with UC in Han Chinese patients, and further implied both IL2 and IL21 as genetic risk factors for UC. Han Chinese UC patients share part of their genetic susceptibility with Caucasian patients.

Meta-analysis identifies 29 additional ulcerative colitis risk loci, increasing the number of confirmed associations to 47.

Genome-wide association studies (GWAS) and candidate gene studies in ulcerative colitis (UC) have identified 18 susceptibility loci. We conducted a meta-analysis of 6 UC GWAS, comprising 6,687 cases and 19,718 controls, and followed-up the top association signals in 9,628 cases and 12,917 controls. We identified 29 additional risk loci (P<5×10-8), increasing the number of UC associated loci to 47. After annotating associated regions using GRAIL, eQTL data and correlations with non-synonymous SNPs, we identified many candidate genes providing potentially important insights into disease pathogenesis, including IL1R2, IL8RA/B, IL7R, IL12B, DAP, PRDM1, JAK2, IRF5, GNA12 and LSP1. The total number of confirmed inflammatory bowel disease (IBD) risk loci is now 99, including a minimum of 28 shared association signals between Crohn’s disease (CD) and UC.

Association of inflammatory bowel disease risk loci with sarcoidosis, and its acute and chronic subphenotypes

Sarcoidosis is a complex granulomatous inflammatory disorder that shares several clinical and pathogenic features with inflammatory bowel disease (IBD). Postulating a common genetic basis of inflammatory diseases, we tested 106 single-nucleotide polymorphisms (SNPs) that are known or have been suggested to be associated with IBD for a potential association with sarcoidosis and its acute and chronic subphenotypes. We genotyped 1,996 German sarcoidosis patients, comprising 648 acutely and 1,161 chronically affected individuals, 2,622 control subjects, and 342 German trios with affected offspring using SNPlex™ technology. The nonsynonymous SNP rs11209026 (Arg381Gln) in the interleukin (IL)-23 receptor (IL23R) gene was associated with chronic sarcoidosis (OR 0.63; p = 5.58×10(-5)), which was supported by the result of a transmission disequilibrium test analysis in the independent family sample (OR 0.50; p = 0.031). Marker rs12035082 located at chromosome 1q24.3 was found to be associated with the acute subphenotype (OR 1.36; p = 6.80×10(-7)) and rs916977 (HERC2 locus; OR 1.30; p = 4.49×10(-5)) was associated with sarcoidosis. Our results highlight the potential importance of the IL-23 signalling pathway for the development of chronic sarcoidosis. The finding links sarcoidosis pathogenesis to other inflammatory conditions and may contribute to new hypotheses on disease mechanisms.

Ulcerative colitis–risk loci on chromosomes 1p36 and 12q15 found by genome-wide association study

Ulcerative colitis is a chronic inflammatory disease of the colon that presents as diarrhea and gastrointestinal bleeding. We performed a genome-wide association study using DNA samples from 1,052 individuals with ulcerative colitis and pre-existing data from 2,571 controls, all of European ancestry. In an analysis that controlled for gender and population structure, ulcerative colitis loci attaining genome-wide significance and subsequent replication in two independent populations were identified on chromosomes 1p36 (rs6426833, combined P = 5.1×10−13, combined OR = 0.73) and 12q15 (rs1558744, combined P = 2.5×10−12, combined OR = 1.35). In addition, combined genome-wide significant evidence for association was found in a region spanning BTNL2 to HLA-DQB1 on chromosome 6p21 (rs2395185, combined P = 1.0×10−16, combined OR = 0.66) and at the IL23R locus on chromosome 1p31 (rs11209026, combined P = 1.3×10−8, combined OR = 0.56; rs10889677, combined P = 1.3×10−8, combined OR = 1.29).