Crohn's Disease Risk Alleles Research Articles

Denosumab Regulates Gut Microbiota Composition and Cytokines in Dinitrobenzene Sulfonic Acid (DNBS)-Experimental Colitis

The pro-inflammatory mediator receptor activator of nuclear factor-kappa B ligand (RANKL) plays a significant role in the development of rheumatoid arthritis; however, its role in inflammatory bowel disease is unknown. Genome-wide association meta-analysis for Crohn’s disease (CD) identified a variant near the TNFSF11 gene that encodes RANKL and CD risk allele increased expression of RANKL in specific cell lines. This study aims to elucidate if the RANKL inhibitor denosumab can reduce the severity of experimental colitis and modify the gut microbiota composition using murine dinitrobenzenesulfonic acid (DNBS)-experimental model of colitis mimicking CD. In colitic conditions, denosumab treatment significantly decreased the pro-inflammatory cytokines IL-6, IL-1β, and TNF-α within the colonic mucosa. Moreover, colitis was accompanied by disruption of gut microbiota, and preventative treatment with denosumab modulated this disruption. Denosumab treatment also modified the alpha- and beta diversity of colonic mucosa and fecal microbiota. These results provide a rationale for considering denosumab as a future potential therapy in CD; however, more detailed experimental and clinical studies are warranted.

Functional variants in the LRRK2 gene confer shared effects on risk for Crohn's disease and Parkinson's disease.

Crohn's disease (CD), a form of inflammatory bowel disease, has a higher prevalence in Ashkenazi Jewish than in non-Jewish European populations. To define the role of nonsynonymous mutations, we performed exome sequencing of Ashkenazi Jewish patients with CD, followed by array-based genotyping and association analysis in 2066 CD cases and 3633 healthy controls. We detected association signals in the LRRK2 gene that conferred risk for CD (N2081D variant, P = 9.5 × 10-10) or protection from CD (N551K variant, tagging R1398H-associated haplotype, P = 3.3 × 10-8). These variants affected CD age of onset, disease location, LRRK2 activity, and autophagy. Bayesian network analysis of CD patient intestinal tissue further implicated LRRK2 in CD pathogenesis. Analysis of the extended LRRK2 locus in 24,570 CD cases, patients with Parkinson's disease (PD), and healthy controls revealed extensive pleiotropy, with shared genetic effects between CD and PD in both Ashkenazi Jewish and non-Jewish cohorts. The LRRK2 N2081D CD risk allele is located in the same kinase domain as G2019S, a mutation that is the major genetic cause of familial and sporadic PD. Like the G2019S mutation, the N2081D variant was associated with increased kinase activity, whereas neither N551K nor R1398H variants on the protective haplotype altered kinase activity. We also confirmed that R1398H, but not N551K, increased guanosine triphosphate binding and hydrolyzing enzyme (GTPase) activity, thereby deactivating LRRK2. The presence of shared LRRK2 alleles in CD and PD provides refined insight into disease mechanisms and may have major implications for the treatment of these two seemingly unrelated diseases.

A Pleiotropic Missense Variant in SLC39A8 Is Associated With Crohn’s Disease and Human Gut Microbiome Composition

Genome-wide association studies have identified 200 inflammatory bowel disease (IBD) loci, but the genetic architecture of Crohn's disease (CD) and ulcerative colitis remain incompletely defined. Here, we aimed to identify novel associations between IBD and functional genetic variants using the Illumina ExomeChip (San Diego, CA). Genotyping was performed in 10,523 IBD cases and 5726 non-IBD controls. There were 91,713 functional single-nucleotide polymorphism loci in coding regions analyzed. A novel identified association was replicated further in 2 independent cohorts. We further examined the association of the identified single-nucleotide polymorphism with microbiota from 338 mucosal lavage samples in the Mucosal Luminal Interface cohort measured using 16S sequencing. We identified an association between CD and a missense variant encoding alanine or threonine at position 391 in the zinc transporter solute carrier family 39, member 8 protein (SLC39A8 alanine 391 threonine, rs13107325) and replicated the association with CD in 2 replication cohorts (combined meta-analysis P= 5.55× 10(-13)). This variant has been associated previously with distinct phenotypes including obesity, lipid levels, blood pressure, and schizophrenia. We subsequently determined that the CD risk allele was associated with altered colonic mucosal microbiome composition in both healthy controls (P= .009) and CD cases(P= .0009). Moreover, microbes depleted in healthycarriers strongly overlap with those reduced in CD patients (P=9.24× 10(-16)) and overweight individuals (P=6.73×10(-16)). Our results suggest that anSLC39A8-dependent shift in the gut microbiome could explain itspleiotropic effects on multiple complex diseases includingCD.

Defective macrophage handling of Escherichia coli in Crohn's disease.

Escherichia coli can be isolated from lamina propria macrophages in Crohn's disease (CD), and their intramacrophage persistence may provide a stimulus for inflammation. To further determine the contributions of macrophage dysfunction and E. coli pathogenicity to this, we aimed to compare in vitro functioning of macrophages from patients with CD and healthy controls (HC) in response to infection with CD-derived adherent-invasive E. coli (AIEC) and less pathogenic E. coli strains. Monocyte-derived macrophages were cultured from patients with CD and HC. Intramacrophage survival of E. coli strains (CD-derived adherent-invasive [AI] and non-AI strains and laboratory strain K-12) was compared. Macrophage cytokine release (tumor necrosis factor alpha [TNFα], interleukin [IL]-23, IL-8 and IL-10) and monocyte phagoctyosis and respiratory burst function were measured after E. coli infection. For CD patients, laboratory data were correlated with clinical phenotype, use of immunomodulation, and CD risk alleles (NOD2, IL-23R, ATG16L1 and IRGM). Attenuated TNFα and IL-23 release from CD macrophages was found after infection with all E. coli strains. There was prolonged survival of CD-derived AIEC, CD-derived non-AIEC and E. coli K-12 in macrophages from CD patients compared to within those from HC. No abnormality of monocyte phagocytosis or respiratory burst function was detected in CD. Macrophage dysfunction in CD was not influenced by phenotype, use of immunomodulation or genotype. CD macrophage responses to infection with E. coli are deficient, regardless of clinical phenotype, CD genotype or E. coli pathogenicity. This suggests host immunodeficiency is an important contributor to intramacrophage E. coli persistence in CD.

Granulocyte–Macrophage Colony-Stimulating Factor Autoantibodies

Neutralizing autoantibodies (Abs) against granulocyte-macrophage colony-stimulating factor (GM-CSF Ab) have been associated with stricturing ileal Crohn's disease (CD) in a largely pediatric patient cohort (total 394, adult CD 57). The aim of this study was to examine this association in 2 independent predominantly adult inflammatory bowel disease patient cohorts. Serum samples from 742 subjects from the NIDDK IBD Genetics Consortium and 736 subjects from Australia were analyzed for GM-CSF Ab and genetic markers. We conducted multiple regression analysis with backward elimination to assess the contribution of GM-CSF Ab levels and established CD risk alleles and smoking on ileal disease location in the 477 combined CD subjects from both cohorts. We also determined associations of GM-CSF Ab levels with complications requiring surgical intervention in combined CD subjects in both cohorts. Serum samples from patients with CD expressed significantly higher concentrations of GM-CSF Ab when compared with ulcerative colitis or controls in each cohort. Nonsmokers with ileal CD expressed significantly higher GM-CSF Ab concentrations in the Australian cohort (P = 0.002). Elevated GM-CSF Ab, ileal disease location, and disease duration more than 3 years were independently associated with stricturing/penetrating behavior and intestinal resection for CD. The expression of high GM-CSF Ab is a risk marker for aggressive CD behavior and complications including surgery. Modifying factors include environmental exposure to smoking and genetic risk markers.

975 Novel Associations of Uncommon Crohn's Disease Risk Alleles With Higher Frequencies in the Ashkenazi Jewish Population

975 Novel Associations of Uncommon Crohn's Disease Risk Alleles With Higher Frequencies in the Ashkenazi Jewish Population

Association Between Variants of PRDM1 and NDP52 and Crohn's Disease, Based on Exome Sequencing and Functional Studies

Genome-wide association studies (GWAS) have identified 140 Crohn's disease (CD) susceptibility loci. For most loci, the variants that cause disease are not known and the genes affected by these variants have not been identified. We aimed to identify variants that cause CD through detailed sequencing, genetic association, expression, and functional studies. We sequenced whole exomes of 42 unrelated subjects with CD and 5 healthy subjects (controls) and then filtered single nucleotide variants by incorporating association results from meta-analyses of CD GWAS and in silico mutation effect prediction algorithms. We then genotyped 9348 subjects with CD, 2868 subjects with ulcerative colitis, and 14,567 control subjects and associated variants analyzed in functional studies using materials from subjects and controls and in vitro model systems. We identified rare missense mutations in PR domain-containing 1 (PRDM1) and associated these with CD. These mutations increased proliferation of T cells and secretion of cytokines on activation and increased expression of the adhesion molecule L-selectin. A common CD risk allele, identified in GWAS, correlated with reduced expression of PRDM1 in ileal biopsy specimens and peripheral blood mononuclear cells (combined P = 1.6 × 10(-8)). We identified an association between CD and a common missense variant, Val248Ala, in nuclear domain 10 protein 52 (NDP52) (P = 4.83 × 10(-9)). We found that this variant impairs the regulatory functions of NDP52 to inhibit nuclear factor κB activation of genes that regulate inflammation and affect the stability of proteins in Toll-like receptor pathways. We have extended the results of GWAS and provide evidence that variants in PRDM1 and NDP52 determine susceptibility to CD. PRDM1 maps adjacent to a CD interval identified in GWAS and encodes a transcription factor expressed by T and B cells. NDP52 is an adaptor protein that functions in selective autophagy of intracellular bacteria and signaling molecules, supporting the role of autophagy in the pathogenesis of CD.

A Novel Approach to Detect Cumulative Genetic Effects and Genetic Interactions in Crohn’s Disease

Genome-wide association studies have identified at least 71 Crohn's disease (CD) genetic risk loci, but the role of gene-gene interactions is unclear. The value of genetic variants in clinical practice is not defined because of limited explained heritability. We examined model predictability of combining the 71 CD risk alleles and genetic interactions in an ongoing inflammatory bowel disease genome-wide association study. The Wellcome Trust Case Control Consortium inflammatory bowel disease genome-wide association study was used as a replicate cohort. We used logic regression, an adaptive regression methodology, to search for high-order binary predictors (e.g., single-nucleotide polymorphism [SNP] interactions). The combined 71 CD SNPs had good CD risk predictability (area under the curve of 0.75 and 0.73 in the 2 cohorts). Higher cumulative allele score predicted higher CD risk, but a relatively small difference in cumulative allele scores was observed between CD and controls (49 versus 47, P < 0.001). Through LR, we identified high-order genetic interactions and significantly improved the model predictability (area under the curve, from 0.75 to 0.77, P < 0.0001). A genetic interaction model, including NOD2, ATG16L1, IL10/IL19, C13orf31, and chr21q loci, was discovered and successfully replicated in the independent Wellcome Trust Case Control Consortium cohort. The explained heritability of the 71 CD SNPs alone was 24% and increased to 27% after adding the genetic interactions. A novel approach allowed the identification and replication of genetic interactions among NOD2, ATG16L1, IL10/IL19, C13orf31, and chr21q loci. CD risk can be predicted by a model of 71 CD loci and improved by adding genetic interactions.

PTGER4 Expression-Modulating Polymorphisms in the 5p13.1 Region Predispose to Crohn's Disease and Affect NF-κB and XBP1 Binding Sites

BackgroundGenome-wide association studies identified a PTGER4 expression-modulating region on chromosome 5p13.1 as Crohn's disease (CD) susceptibility region. The study aim was to test this association in a large cohort of patients with inflammatory bowel disease (IBD) and to elucidate genotypic and phenotypic interactions with other IBD genes.Methodology/Principal FindingsA total of 7073 patients and controls were genotyped: 844 CD and 471 patients with ulcerative colitis and 1488 controls were analyzed for the single nucleotide polymorphisms (SNPs) rs4495224 and rs7720838 on chromosome 5p13.1. The study included two replication cohorts of North American (CD: n = 684; controls: n = 1440) and of German origin (CD: n = 1098; controls: n = 1048). Genotype-phenotype, epistasis and transcription factor binding analyses were performed. In the discovery cohort, an association of rs4495224 (p = 4.10×10−5; 0.76 [0.67–0.87]) and of rs7720838 (p = 6.91×10−4; 0.81 [0.71–0.91]) with susceptibility to CD was demonstrated. These associations were confirmed in both replication cohorts. In silico analysis predicted rs4495224 and rs7720838 as essential parts of binding sites for the transcription factors NF-κB and XBP1 with higher binding scores for carriers of the CD risk alleles, providing an explanation of how these SNPs might contribute to increased PTGER4 expression. There was no association of the PTGER4 SNPs with IBD phenotypes. Epistasis detected between 5p13.1 and ATG16L1 for CD susceptibility in the discovery cohort (p = 5.99×10−7 for rs7720838 and rs2241880) could not be replicated in both replication cohorts arguing against a major role of this gene-gene interaction in the susceptibility to CD.Conclusions/SignificanceWe confirmed 5p13.1 as a major CD susceptibility locus and demonstrate by in silico analysis rs4495224 and rs7720838 as part of binding sites for NF-κB and XBP1. Further functional studies are necessary to confirm the results of our in silico analysis and to analyze if changes in PTGER4 expression modulate CD susceptibility.

Combined Analysis of Genome-wide Association Studies for Crohn Disease and Psoriasis Identifies Seven Shared Susceptibility Loci

Psoriasis (PS) and Crohn disease (CD) have been shown to be epidemiologically, pathologically, and therapeutically connected, but little is known about their shared genetic causes. We performed meta-analyses of five published genome-wide association studies on PS (2,529 cases and 4,955 controls) and CD (2,142 cases and 5,505 controls), followed up 20 loci that showed strongest evidence for shared disease association and, furthermore, tested cross-disease associations for previously reported PS and CD risk alleles in additional6,115 PS cases, 4,073 CD cases, and 10,100 controls. We identified seven susceptibility loci outside the human leukocyte antigen region (9p24 near JAK2, 10q22 at ZMIZ1, 11q13 near PRDX5, 16p13 near SOCS1, 17q21 at STAT3, 19p13 near FUT2, and 22q11 at YDJC) shared between PS and CD with genome-wide significance (p < 5× 10(-8)) and confirmed four already established PS and CD risk loci (IL23R, IL12B, REL, and TYK2). Three of the shared loci are also genome-wide significantly associated with PS alone (10q22 at ZMIZ1, p(rs1250544) = 3.53×10(-8), 11q13 near PRDX5, p(rs694739) = 3.71× 10(-09), 22q11 at YDJC, p(rs181359) = 8.02× 10(-10)). In addition, we identified one susceptibility locus for CD (16p13 near SOCS1, p(rs4780355) = 4.99× 10(-8)). Refinement of association signals identified shared genome-wide significant associations for exonic SNPs at 10q22 (ZMIZ1) and insilico expression quantitative trait locus analyses revealed that the associations at ZMIZ1 and near SOCS1 have a potential functional effect on gene expression. Our results show the usefulness of joint analyses of clinically distinct immune-mediated diseases and enlarge the map of shared genetic risk loci.

Crohn's Disease Risk Alleles on the NOD2 Locus Have Been Maintained by Natural Selection on Standing Variation

Risk alleles for complex diseases are widely spread throughout human populations. However, little is known about the geographic distribution and frequencies of risk alleles, which may contribute to differences in disease susceptibility and prevalence among populations. Here, we focus on Crohn's disease (CD) as a model for the evolutionary study of complex disease alleles. Recent genome-wide association studies and classical linkage analyses have identified more than 70 susceptible genomic regions for CD in Europeans, but only a few have been confirmed in non-European populations. Our analysis of eight European-specific susceptibility genes using HapMap data shows that at the NOD2 locus the CD-risk alleles are linked with a haplotype specific to CEU at a frequency that is significantly higher compared with the entire genome. We subsequently examined nine global populations and found that the CD-risk alleles spread through hitchhiking with a high-frequency haplotype (H1) exclusive to Europeans. To examine the neutrality of NOD2, we performed phylogenetic network analyses, coalescent simulation, protein structural prediction, characterization of mutation patterns, and estimations of population growth and time to most recent common ancestor (TMRCA). We found that while H1 was significantly prevalent in European populations, the H1 TMRCA predated human migration out of Africa. H1 is likely to have undergone negative selection because 1) the root of H1 genealogy is defined by a preexisting amino acid substitution that causes serious conformational changes to the NOD2 protein, 2) the haplotype has almost become extinct in Africa, and 3) the haplotype has not been affected by the recent European expansion reflected in the other haplotypes. Nevertheless, H1 has survived in European populations, suggesting that the haplotype is advantageous to this group. We propose that several CD-risk alleles, which destabilize and disrupt the NOD2 protein, have been maintained by natural selection on standing variation because the deleterious haplotype of NOD2 is advantageous in diploid individuals due to heterozygote advantage and/or intergenic interactions.

Association of TNFSF15 polymorphism with irritable bowel syndrome

BackgroundIrritable bowel syndrome (IBS) is the most common gastrointestinal disorder, affecting more than 10% of the general population worldwide. Although a genetic component is suspected, unambiguous susceptibility genes have so...

Effect of Crohn's Disease Risk Alleles on Enteric Microbiota Marker Paper

AbstractThis UH2/UH3 demonstration project entitled “Effects of Crohn’s disease risk alleles on enteric microbiota” is focused on characterizing intestinal associated microbiota in patients with ileal Crohn’s disease (ileal CD), ulcerative colitis (UC) and control patients without inflammatory bowel diseases (non-IBD). We hypothesize that genetic factors that affect Paneth cell function, contribute to compositional changes in intestinal microbiota. These changes in microbiota may lead to reduction of protective commensal organisms and increased numbers of aggressive organisms that incite intestinal inflammation. This hypothesis is being tested by high throughput 16S rRNA sequence analysis of de-identified ileal and colonic tissues that have been archived at Washington University St. Louis, University of North Carolina, Mount Sinai Hospital and the Cleveland Clinic. Multivariate analysis of the metagenomic data will be conducted with genotyping metadata (highly reproducible CD risk alleles, including NOD2 and ATG16L1) and phenotyping metadata (e.g. age, gender, race, body mass index, medications and smoking). Shotgun sequencing will be performed on selected fecal specimens linked to ileal tissues to identify additional, or auxiliary, or synergistic pathogenic factors or other functional changes in the microbiome. Because members of this research team have observed that a chronic viral infection is required for the Paneth cell defect in Atg16l1 hypomorphic mice, a major focus of these studies will be towards identifying potential viral triggers for the defective Paneth cell phenotype in individuals harboring the ATG16L1 risk allele. Novel genetic probes for protective and aggressive organisms will be developed by mining bacterial genome and shotgun sequencing data. Genomic sequences will be produced for candidate protective and aggressive strains (e.g. adherent-invasive strains of E. coli) isolated from human intestinal tissues where there is limited existing genome information. Quantitative qPCR assays using the novel as well as established genetic probes will be conducted to test the hypothesis that an imbalance between protective and aggressive organisms is associated with genetic factors that affect Paneth cell function.Our combined expertise in multiple disciplines across multiple institutions, our demonstrated ability to collect a large number of well-phenotyped samples with longitudinal clinical information that will be linked to host response and morphologic studies, and our consortium’s capacity for high-throughput sequencing will be used to investigate how alterations in human microbiome relate to CD risk alleles and CD pathogenesis.

Association of Linear Growth Impairment in Pediatric Crohn's Disease and a Known Height Locus: A Pilot Study

The etiology of growth impairment in Crohn's disease (CD) has been inadequately explained by nutritional, hormonal, and/or disease-related factors, suggesting that genetics may be an additional contributor. The aim of this cross-sectional study was to investigate genetic variants associated with linear growth in pediatric-onset CD. We genotyped 951 subjects (317 CD patient-parent trios) for 64 polymorphisms within 14 CD-susceptibility and 23 stature-associated loci. Patient height-for-age Z-score < -1.64 was used to dichotomize probands into growth-impaired and nongrowth-impaired groups. The transmission disequilibrium test (TDT) was used to study association to growth impairment. There was a significant association between growth impairment in CD (height-for-age Z-score < -1.64) and a stature-related polymorphism in the dymeclin gene DYM (rs8099594) (OR = 3.2, CI [1.57-6.51], p = 0.0007). In addition, there was nominal over-transmission of two CD-susceptibility alleles, 10q21.1 intergenic region (rs10761659) and ATG16L1 (rs10210302), in growth-impaired CD children (OR = 2.36, CI [1.26-4.41] p = 0.0056 and OR = 2.45, CI [1.22-4.95] p = 0.0094, respectively). Our data indicate that genetic influences due to stature-associated and possibly CD risk alleles may predispose CD patients to alterations in linear growth. This is the first report of a link between a stature-associated locus and growth impairment in CD.

W1234 Non-Synonymous Polymorphisms in the Tryptophan Catabolism Pathway: Correlation to Crohn's Disease Risk and Phenotype

Background. Clinical data support the existence of discrete subsets of Crohn's disease (CD) patients by disease location. Previous genotype-phenotype analyses have linked the NOD2 and ATG16L1 risk alleles with ileal disease location. Aim. To elucidate novel genotypesubphenotype correlations between 28 established CD risk alleles and disease location (Montreal classification).Methods. We reviewed our established inflammatory bowel disease relational genotypic-phenotypic database. We identified 600 CD patients that had been genotyped for 28 established CD risk alleles that were selected based on previous genome wide association studies [Barrett et al. Nature Genetics 2008; 40:955]. Genotyping was conducted using Taqman allelic discrimination and Sequenom MassARRAY®. The patients were classified as risk (at least one risk allele) or non-risk (no risk allele). In addition, the three major NOD2 risk alleles (Leu1007fs, R702W and G908R) were combined as a single superallele where the NOD2 risk group harbored at least one of the three risk alleles and the NOD2 non-risk group had none of the three risk alleles. The patients were subphenotyped with respect to their maximal disease location using the Montreal classification. Genotypesubphenotype analysis was carried out usingmultinomial logistic regression analysis.Results. The distribution of disease locations were 274 for L1 (ileal), 126 for L2 (colonic), 187 for L3 (ileocolonic), and 3 for L4 (upper small bowel). Five CD risk alleles were significantly associated with disease location (L1 vs L2 vs L3, P<0.05, see Table 1). We detected no effect of gender, race or smoking on disease location. Conclusions. These results support the concept that there is a genetic basis for CD subphenotypes by disease location. Although both NOD2 and ATG16L1 have been associated with ileal disease, harboring a NOD2 risk allele is associated with L1 disease location, whereas harboring the ATG16L1T300A risk allele is associated with L3 disease location. The TNSF15 risk allele is associated with L2 disease location, whereas the X21q21 risk allele is associated with L3 disease location. Table 1. Significant CD risk alleles

W1235 Inflammatory Bowel Disease (IBD)-Associated DNA Methylation in B Cells From IBD Patients

Background. Clinical data support the existence of discrete subsets of Crohn's disease (CD) patients by disease location. Previous genotype-phenotype analyses have linked the NOD2 and ATG16L1 risk alleles with ileal disease location. Aim. To elucidate novel genotypesubphenotype correlations between 28 established CD risk alleles and disease location (Montreal classification).Methods. We reviewed our established inflammatory bowel disease relational genotypic-phenotypic database. We identified 600 CD patients that had been genotyped for 28 established CD risk alleles that were selected based on previous genome wide association studies [Barrett et al. Nature Genetics 2008; 40:955]. Genotyping was conducted using Taqman allelic discrimination and Sequenom MassARRAY®. The patients were classified as risk (at least one risk allele) or non-risk (no risk allele). In addition, the three major NOD2 risk alleles (Leu1007fs, R702W and G908R) were combined as a single superallele where the NOD2 risk group harbored at least one of the three risk alleles and the NOD2 non-risk group had none of the three risk alleles. The patients were subphenotyped with respect to their maximal disease location using the Montreal classification. Genotypesubphenotype analysis was carried out usingmultinomial logistic regression analysis.Results. The distribution of disease locations were 274 for L1 (ileal), 126 for L2 (colonic), 187 for L3 (ileocolonic), and 3 for L4 (upper small bowel). Five CD risk alleles were significantly associated with disease location (L1 vs L2 vs L3, P<0.05, see Table 1). We detected no effect of gender, race or smoking on disease location. Conclusions. These results support the concept that there is a genetic basis for CD subphenotypes by disease location. Although both NOD2 and ATG16L1 have been associated with ileal disease, harboring a NOD2 risk allele is associated with L1 disease location, whereas harboring the ATG16L1T300A risk allele is associated with L3 disease location. The TNSF15 risk allele is associated with L2 disease location, whereas the X21q21 risk allele is associated with L3 disease location. Table 1. Significant CD risk alleles

W1236 NOD2 Mutations Compromise Host Defense Mechanisms to Enteric Bacteria as Shown by Decreased NF-kB in Human B Cells After Muramyl Dipeptide (MDP) Stimulation

Background. Clinical data support the existence of discrete subsets of Crohn's disease (CD) patients by disease location. Previous genotype-phenotype analyses have linked the NOD2 and ATG16L1 risk alleles with ileal disease location. Aim. To elucidate novel genotypesubphenotype correlations between 28 established CD risk alleles and disease location (Montreal classification).Methods. We reviewed our established inflammatory bowel disease relational genotypic-phenotypic database. We identified 600 CD patients that had been genotyped for 28 established CD risk alleles that were selected based on previous genome wide association studies [Barrett et al. Nature Genetics 2008; 40:955]. Genotyping was conducted using Taqman allelic discrimination and Sequenom MassARRAY®. The patients were classified as risk (at least one risk allele) or non-risk (no risk allele). In addition, the three major NOD2 risk alleles (Leu1007fs, R702W and G908R) were combined as a single superallele where the NOD2 risk group harbored at least one of the three risk alleles and the NOD2 non-risk group had none of the three risk alleles. The patients were subphenotyped with respect to their maximal disease location using the Montreal classification. Genotypesubphenotype analysis was carried out usingmultinomial logistic regression analysis.Results. The distribution of disease locations were 274 for L1 (ileal), 126 for L2 (colonic), 187 for L3 (ileocolonic), and 3 for L4 (upper small bowel). Five CD risk alleles were significantly associated with disease location (L1 vs L2 vs L3, P<0.05, see Table 1). We detected no effect of gender, race or smoking on disease location. Conclusions. These results support the concept that there is a genetic basis for CD subphenotypes by disease location. Although both NOD2 and ATG16L1 have been associated with ileal disease, harboring a NOD2 risk allele is associated with L1 disease location, whereas harboring the ATG16L1T300A risk allele is associated with L3 disease location. The TNSF15 risk allele is associated with L2 disease location, whereas the X21q21 risk allele is associated with L3 disease location. Table 1. Significant CD risk alleles

W1233 Genotype-Subphenotype Correlations Between Established Crohn's Disease Risk Alleles and Disease Location

W1233 Genotype-Subphenotype Correlations Between Established Crohn's Disease Risk Alleles and Disease Location

T1557 Bowel Preparation in the West of Scotland. Complication Rates and Survival Outcomes for Elective Colon Surgery in a Managed Clinical Network Setting

PURPOSE: Perianal manifestations of Crohn's Disease (CD) are common and have a significant effect on disease morbidity and patient quality of life. Recent studies suggest that perianal CD may be a distinct phenotype and as such may be associated with specific susceptibility genes and environmental factors. The objective of this study was to examine the relationship between genotype and phenotype in perianal CD. METHODS: Review of a prospectively maintained, IRB-approved institutional database of patients with CD was performed for phenotypic data on patients with and without perianal CD. Genotype data was available for disease associated risk alleles for NOD2, IBD5, ATG16L1, IRGM, and IL23R. Univariate analysis was performed to evaluate differences in genotype and phenotype frequencies between patients with and without perianal CD. Statistical analysis was performed using chi square analysis with significance set at p<0.05. RESULTS: Of 710 patients, 236 (33%) were identified as having perianal CD. There was no difference between patients with and without perianal CD with respect to gender, race, age at diagnosis, family history of IBD, and current or past smoking. Patients with perianal CD were significantly more likely to have received anti-TNF therapy than patients without perianal CD (OR 2.28, 95% CI 1.513.45, p<0.0001). There was a trend toward increased antibiotic therapy in patients with perianal CD (OR 1.58, 95% CI 0.99-2.54, p=0.06). The presence of rectal disease was significantly higher in patients with perianal CD than patients without perianal CD (odds ratio [OR] 1.65, 95% CI 1.15-2.36, p=0.006). Genotype data was available on 417 patients. There was a trend toward association of perianal CD and IBD5 risk allele IGR2096 (OR 1.56, 95% CI 0.95-2.57, p=0.08). No association was found between perianal CD and the studied risk alleles for NOD2, ATG16L1, IRGM and IL23R. The requirement for fecal diversion was used as a surrogate marker for the severity of perianal CD. Diversion for perianal CD occurred in 42 patients (18%). There was no significant association of diversion for perianal CD and any of the studied risk alleles. Patients who received anti-TNF therapy were less likely to require diversion for perianal CD (OR 0.28, 95% CI 0.13-0.63, p= 0.001). CONCLUSION: In patients with CD, there is a significant association between rectal involvement and the presence of perianal disease. There is a trend toward association of perianal CD and the presence of IBD5 risk alleles. Anti-TNF therapy is associated with a reduced need for fecal diversion in perianal CD.

T1556 The Role of Genotype and Phenotype in Patients with Perianal Crohn's Disease

PURPOSE: Perianal manifestations of Crohn's Disease (CD) are common and have a significant effect on disease morbidity and patient quality of life. Recent studies suggest that perianal CD may be a distinct phenotype and as such may be associated with specific susceptibility genes and environmental factors. The objective of this study was to examine the relationship between genotype and phenotype in perianal CD. METHODS: Review of a prospectively maintained, IRB-approved institutional database of patients with CD was performed for phenotypic data on patients with and without perianal CD. Genotype data was available for disease associated risk alleles for NOD2, IBD5, ATG16L1, IRGM, and IL23R. Univariate analysis was performed to evaluate differences in genotype and phenotype frequencies between patients with and without perianal CD. Statistical analysis was performed using chi square analysis with significance set at p<0.05. RESULTS: Of 710 patients, 236 (33%) were identified as having perianal CD. There was no difference between patients with and without perianal CD with respect to gender, race, age at diagnosis, family history of IBD, and current or past smoking. Patients with perianal CD were significantly more likely to have received anti-TNF therapy than patients without perianal CD (OR 2.28, 95% CI 1.513.45, p<0.0001). There was a trend toward increased antibiotic therapy in patients with perianal CD (OR 1.58, 95% CI 0.99-2.54, p=0.06). The presence of rectal disease was significantly higher in patients with perianal CD than patients without perianal CD (odds ratio [OR] 1.65, 95% CI 1.15-2.36, p=0.006). Genotype data was available on 417 patients. There was a trend toward association of perianal CD and IBD5 risk allele IGR2096 (OR 1.56, 95% CI 0.95-2.57, p=0.08). No association was found between perianal CD and the studied risk alleles for NOD2, ATG16L1, IRGM and IL23R. The requirement for fecal diversion was used as a surrogate marker for the severity of perianal CD. Diversion for perianal CD occurred in 42 patients (18%). There was no significant association of diversion for perianal CD and any of the studied risk alleles. Patients who received anti-TNF therapy were less likely to require diversion for perianal CD (OR 0.28, 95% CI 0.13-0.63, p= 0.001). CONCLUSION: In patients with CD, there is a significant association between rectal involvement and the presence of perianal disease. There is a trend toward association of perianal CD and the presence of IBD5 risk alleles. Anti-TNF therapy is associated with a reduced need for fecal diversion in perianal CD.