Wolfram Klein

Polymorphisms in the DLG5 and OCTN cation transporter genes in Crohn’s disease

Background and aims: Recent data suggest identification of causal genetic variants for inflammatory bowel disease in the DLG5 gene and in the organic cation transporter (OCTN) cluster, both situated in previously described linkage regions. Patients and methods: The polymorphisms in DLG5 (113 G→A, 4136 C→A, and DLG5_e26), SLC22A4 (1672 C→T), and SLC22A5 (−207 G→C) were assessed in 625 patients with Crohn’s disease (CD), 363 patients with ulcerative colitis (UC), and 1012 healthy controls. Association with disease susceptibility, clinical phenotypes, and possible genetic interactions of these polymorphisms with disease associated CARD15/NOD2 mutations was analysed. Results: No significant association of DLG5 polymorphisms with CD or UC was observed. Homozygosity for the OCTN-TC haplotype was associated with an increased CD risk (OR = 1.65), which was even greater in the presence of CARD15 mutations. Genotype-phenotype analysis revealed that this association was particularly strong in patients with colonic disease. The TC haplotype was associated with non-fistulising non-fibrostenotic disease, an earlier age of disease onset, and reduced need for surgery. Conclusion: Our observations argue against a role of DLG5 polymorphisms in the susceptibility for inflammatory bowel disease, whereas the OCTN polymorphisms are associated with CD. However, due to the comparable weak association observed herein, extended linkage disequilibrium analyses of these variants with the IBD5 haplotype tagged single nucleotide polymorphims might be advisable before definitive conclusions about their causative role in CD can be drawn.

rs1004819 Is the Main Disease-Associated IL23R Variant in German Crohn's Disease Patients: Combined Analysis of IL23R, CARD15, and OCTN1/2 Variants

Background The IL23R gene has been identified as a susceptibility gene for inflammatory bowel disease (IBD) in the North American population. The aim of our study was to test this association in a large German IBD cohort and to elucidate potential interactions with other IBD genes as well as phenotypic consequences of IL23R variants. Methods Genomic DNA from 2670 Caucasian individuals including 833 patients with Crohns disease (CD), 456 patients with ulcerative colitis (UC), and 1381 healthy unrelated controls was analyzed for 10 IL23R SNPs. Genotyping included the NOD2 variants p.Arg702Trp, p.Gly908Arg, and p.Leu1007fsX1008 and polymorphisms in SLC22A4/OCTN1 (1672 C→T) and SLC22A5/OCTN2 (–207 G→C). Results All IL23R gene variants analyzed displayed highly significant associations with CD. The strongest association was found for the SNP rs1004819 [P = 1.92×10−11; OR 1.56; 95 % CI (1.37–1.78)]. 93.2% of the rs1004819 TT homozygous carriers as compared to 78% of CC wildtype carriers had ileal involvement [P = 0.004; OR 4.24; CI (1.46–12.34)]. The coding SNP rs11209026 (p.Arg381Gln) was protective for CD [P = 8.04×10−8; OR 0.43; CI (0.31–0.59)]. Similar, but weaker associations were found in UC. There was no evidence for epistasis between the IL23R gene and the CD susceptibility genes CARD15 and SLC22A4/5. Conclusion IL23R is an IBD susceptibility gene, but has no epistatic interaction with CARD15 and SLC22A4/5. rs1004819 is the major IL23R variant associated with CD in the German population, while the p.Arg381Gln IL23R variant is a protective marker for CD and UC.

A polymorphism in the CD14 gene is associated with Crohn disease.

Background : Inflammatory bowel diseases (IBD) are multifactorial disorders, characterized by failure to limit the inflammatory response to luminal antigens. Although genetic factors play an important role in the pathogenesis, little is known about the genes accountable. Immune response to intestinal bacteria seems to be crucial in the pathogenesis of IBD. Methods : To evaluate the role of the CD14 gene in IBD, a functionally relevant polymorphism in the promoter region (T/C at position-159) has been genotyped in 219 patients with Crohn disease (CD), 142 patients with ulcerative colitis (UC) and 410 healthy controls by RFLP analysis. Results : T allele and TT genotype frequencies were found increased in CD patients compared to controls ( P c = 0.044 and 0.005, respectively). Conclusion : An altered immune response to LPS seems to play a role in the genetic predisposition to CD but not to UC.

The ATG16L1 gene variants rs2241879 and rs2241880 (T300A) are strongly associated with susceptibility to Crohn's disease in the German population.

OBJECTIVES:We analyzed ATG16L1, a recently identified Crohns disease (CD) susceptibility gene, in a large cohort with inflammatory bowel disease (IBD) including potential interactions with other IBD genes as well as factors regulating its gene expression.METHODS:Genomic DNA from 2,890 Caucasians including 768 patients with CD, 507 patients with ulcerative colitis (UC), and 1,615 healthy controls was analyzed for 9 different ATG16L1 single nucleotide polymorphisms (SNPs). Genotyping included CARD15/NOD2 variants p.Arg702Trp, p.Gly908Arg, and p.Leu1007fsX1008 and polymorphisms in SLC22A4/OCTN1 (1672 C→T) and SLC22A5/OCTN2 (−207 G→C) as well as 10 CD-associated IL23R variants. The transcriptional regulation of ATG16L1 was studied in intestinal epithelial cells following stimulation with Toll-like receptor (TLR) ligands and proinflammatory cytokines and in a murine ileitis model and CD biopsies.RESULTS:All nine ATG16L1 gene variants analyzed displayed highly significant associations with CD demonstrating a CD-protective effect for the minor allele. The strongest associations were found for rs2241879 and the coding SNP rs2241880 (T300A); P = 3.6 × 10−6 and 3.7 × 10−6, respectively (OR 0.74, 95% CI 0.65–0.84 for both variants). The genotype-phenotype analysis revealed no significant associations. In UC, only rs6431660 was weakly disease-associated. There was no evidence for epistasis between the ATG16L1 gene and other susceptibility genes (IL23R, CARD15, SLC22A4/5). ATG16L1 mRNA expression was not upregulated in CD and murine ileitis, and was less than threefold increased in cells stimulated with proinflammatory cytokines and TLR ligands.CONCLUSION:ATG16L1 is a CD susceptibility gene without epistatic interaction with other CD susceptibility genes and is not upregulated in intestinal inflammation.

Novel Genetic Risk Markers for Ulcerative Colitis in the IL2/IL21 Region Are in Epistasis With IL23R and Suggest a Common Genetic Background for Ulcerative Colitis and Celiac Disease

OBJECTIVES:Recently, a genome-wide association study showed that single-nucleotide polymorphisms (SNPs) in the chromosome 4q27 region containing IL2 and IL21 are associated with celiac disease. Given the increased prevalence of inflammatory bowel disease (IBD) among celiac disease patients, we investigated the possible involvement of these SNPs in IBD.METHODS:Five SNPs strongly associated with celiac disease within the KIAA1109/TENR/IL2/IL21 linkage disequilibrium block on chromosome 4q27 and one coding SNP within the IL21 gene were analyzed in a large German IBD cohort. The study population comprised a total of 2,948 Caucasian individuals, including 1,461 IBD patients (ulcerative colitis (UC): n=514, Crohns disease (CD): n=947) and 1,487 healthy unrelated controls.RESULTS:Three of the five celiac disease risk markers had a protective effect on UC susceptibility, and this effect remained significant after correcting for multiple testing: rs6840978: P=0.0082, Pcorr=0.049, odds ratio (OR) 0.77, 95% confidence interval (CI) 0.63–0.93; rs6822844: P=0.0028, Pcorr=0.017, OR 0.73, 95% CI 0.59–0.90; rs13119723: P=0.0058, Pcorr=0.035, OR 0.75, 95% CI 0.61–0.92. A haplotype consisting of the six SNPs tested was markedly associated with UC susceptibility (P=0.0025, Pcorr=0.015, OR 0.72, 95% CI 0.58–0.89). Moreover, in UC, epistasis was observed between the IL23R SNP rs1004819 and three SNPs in the KIAA1109/TENR/IL2/IL21 block (rs13151961, rs13119723, and rs6822844).CONCLUSIONS:Similar to other autoimmune diseases such as celiac disease, rheumatoid arthritis, type 1 diabetes, Graves’ disease, and psoriatic arthritis, genetic variation in the chromosome 4q27 region predisposes to UC, suggesting a common genetic background for these diseases.

Complex genetic predisposition in adult and juvenile rheumatoid arthritis

BackgroundRheumatoid arthritis (RA) and juvenile rheumatoid arthritis (JRA) are complex multifactorial diseases caused by environmental influences and an unknown number of predisposing genes. The present study was undertaken in order to investigate association of polymorphisms in candidate genes with RA and JRA in German subjects.ResultsUp to 200 unrelated German RA and JRA patients each and 300–400 healthy controls have been genotyped for HLA-DRB1, TNFa, TNFA -238a/g, TNFA -308a/g, TNFA -857c/t, TNFR1 -609g/t, TNFR1 P12P, TNFR2 del 15bp, IKBL -332a/g, IKBL -132t/a, IKBL C224R, CTLA4 -318c/t, CTLA4 T17A, PTPRC P57P, MIF -173g/c, the MIF and IFNG microsatellites as well as for D17S795, D17S807, D17S1821 by polyacrylamide gel electrophoresis, single-strand conformation polymorphism analysis, restriction fragment length polymorphism analysis or allele specific hybridization. None of the investigated genetic markers is associated with both, RA and JRA, but there are some statistically significant differences between patients and controls that have to be discussed sensibly.ConclusionsThe difficulty in investigating the genetics of complex disorders like RA and JRA may arise from genetic heterogeneity in the clinically defined disease cohorts (and generally limited power of such studies). In addition, several to many genes appear to be involved in the genetic predisposition, each of which exerting only small effects. The number of investigated patients has to be increased to establish the possibility of subdivison of the patients according their clinical symptoms, severity of disease, HLA status and other genetic characteristics.

Epistasis Between Toll-Like Receptor-9 Polymorphisms and Variants in NOD2 and IL23R Modulates Susceptibility to Crohn's Disease

OBJECTIVES:Recent data suggest functional interactions between NOD2 and other receptors of the innate immune system modulating inflammatory responses. Here we analyzed the role of Toll-like receptor 9 (TLR-9) gene variants with respect to susceptibility to inflammatory bowel disease (IBD) and tested for genetic interactions with NOD2 and other susceptibility genes for Crohns disease (CD).METHODS:The single-nucleotide polymorphisms (SNPs) –1237T/C (rs5743836) and 2848A/G (rs352140=p.Pro545Pro) in TLR9, the main CD-associated variants within the genes for NOD2, IL23R, ATG16L1, and variants in the IBD5 locus and in the DLG5 gene were assessed in 956 patients with IBD (606 CD and 350 ulcerative colitis) and in 792 healthy controls. The associations with disease susceptibility and phenotype, and epistatic gene–gene interactions, were analyzed.RESULTS:The TLR9 −1237T/C polymorphism showed significant interactions with NOD2 mutations. The frequency of −1237C was significantly higher in CD patients with at least one NOD2 mutation (P=0.004 vs. controls, odds ratio (OR) 1.60, 95% confidence interval (CI) (1.15–2.21)) and further increased in CD patients with two mutated NOD2 alleles (P=0.002 vs. controls, OR 2.37, 95% CI (1.35–4.15)). Significant gene–gene interactions were also observed for the TLR9 polymorphism −1237T/C with IL23R variants (most significantly with rs1004819, P=0.0007), with a particular high frequency of –1237C in CD patients carrying CD-protective IL23R variants. Epistatic interactions of the TLR9 −1237T/C SNP were also noted with the DLG5 113G/A variant (P=0.0007).CONCLUSIONS:Our results provide evidence for genetic interactions between polymorphisms in TLR9 and CD-associated variants in NOD2, IL23R, and DLG5, differentially modulating CD susceptibility.

A polymorphism of the NFKBIA gene is associated with Crohn's disease patients lacking a predisposing allele of the CARD15 gene.

Background and aimsNuclear factor kappa-B (NFκB) plays a crucial role in diseases associated with dysregulated immune response. NFκB inhibitor α downregulates the activity of NFκB.Patients and methodsTo evaluate the contribution of the NFκB inhibitor α gene in Crohns disease single nucleotide polymorphisms in the 3′-UTR and at position −420 in the promoter were studied in 259 patients with Crohns disease genotyped for the variations of the CARD15 gene in comparison to 441 healthy controls. Additionally we screened the coding region of the NFκB inhibitor α gene for polymorphisms by SSCP analysis.ResultsIn comparison to controls the A allele and the AA genotype frequencies of the single nucleotide polymorphisms in the 3′-UTR were significantly increased only in Crohns disease patients without a variation in the CARD15 gene. Similarly, the difference between patients harboring no predisposing CARD15 alleles and patients harboring such a variation was significant.ConclusionThe findings indicate that the phenotype Crohns disease is to be substructured with respect to genetic susceptibility.

Evidence for STAT4 as a Common Autoimmune Gene: rs7574865 Is Associated with Colonic Crohn's Disease and Early Disease Onset

Background Recent studies demonstrated an association of STAT4 variants with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), indicating that multiple autoimmune diseases share common susceptibility genes. We therefore investigated the influence of STAT4 variants on the susceptibility and phenotype of inflammatory bowel diseases (IBD) in a large patient and control cohort. Methodology/Principal Findings Genomic DNA from 2704 individuals of Caucasian origin including 857 patients with Crohns disease (CD), 464 patients with ulcerative colitis (UC), and 1383 healthy, unrelated controls was analyzed for seven SNPs in the STAT4 gene (rs11889341, rs7574865, rs7568275, rs8179673, rs10181656, rs7582694, rs10174238). In addition, a detailed genotype-phenotype analysis was performed. Our analysis revealed an association of the STAT4 SNP rs7574865 with overall decreased susceptibility to CD (p = 0.047, OR 0.86 [95% CI 0.74–0.99]). However, compared to CD patients carrying the wild type genotype, the STAT4 SNP rs7574865 was significantly associated with early CD onset (p = 0.021) and colonic CD (p = 0.008; OR = 4.60, 95% CI 1.63–12.96). For two other STAT4 variants, there was a trend towards protection against CD susceptibility (rs7568275, p = 0.058, OR 0.86 [95% CI 0.74–1.00]; rs10174238, p = 0.057, OR 0.86 [95% CI 0.75–1.00]). In contrast, we did not observe any association with UC susceptibility. Evidence for weak gene-gene interaction of STAT4 with the IL23R SNP rs11209026 was lost after Bonferroni correction. Conclusions/Significance Our results identified the STAT4 SNP rs7574865 as a disease-modifying gene variant in colonic CD. However, in contrast to SLE and RA, the effect of rs7574865 on CD susceptibility is only weak.

Mutations in the calcium-sensing receptor: A new genetic risk factor for chronic pancreatitis?

Objective. In 2003 we identified a family with familial hypocalciuric hypercalcemia (FHH) (heterozygous CASR gene mutation L173P) and a mutation in the pancreatic secretory trypsin inhibitor gene (SPINK1) (N34S). While family members with an isolated calcium-sensing receptor gene (CASR) mutation remained healthy, a combination of the CASR and SPINK1 gene mutation caused chronic pancreatitis (CP). We thus speculate that the combination of two genetic defects affecting calcium homeostasis and pancreatic enzyme activation might represent a novel approach in chronic inherited pancreatic disease. We therefore sought to explore whether CASR gene mutations were prevalent in a cohort of patients with CP and confirmed SPINK1 mutations. Material and methods. A cohort of 19 families (n=170) with a history of idiopathic CP (ICP) was screened for mutations within the CASR gene; 104 members of that cohort had a mutation (N34S) within the SPINK1 gene and 66 of those were suffering from CP. The entire CASR gene was screened for single strand conformation polymorphism under varying polyacrylamide gel conditions and subjected to direct dideoxy nucleotide sequencing of amplified cDNA. Results. Single-strand conformation polymorphisms were observed in 59 samples, clustering of exons 3, 4 and 7. DNA sequence analysis revealed a yet unreported missense mutation in exon 7 (R896H) and two conservative mutations in exon 4 (F391F) and exon 7 (E790E). Furthermore, an intronic polymorphism in nucleotide position 493-19 G > A was detected in 19 out of 170 members of that cohort. Conclusions. We identified three novel calcium-sensing receptor gene mutations (1 missense mutation, 2 silent mutations and 1 intronic polymorphism) in a cohort of 19 families with ICP. In particular, the kindred with the R896H mutation presenting with a similar pedigree to the family described above may indicate a role for CASR gene mutations in SPINK1-related CP. Again, only the patient with the combination of both CASR and N34S SPINK1 gene mutation developed pancreatitis, whereas in the healthy parents and children only an isolated CASR or N34S SPINK1 gene mutation could be detected. We suggest that the CASR gene is a novel yet undetected co-factor in a multifactorial genetic setting of SPINK1-related pancreatitis that alters the susceptibility for pancreatitis in these patients.