Susanna Nikolaus

Association between insertion mutation in NOD2 gene and Crohn's disease in German and British populations

Background Genetic predisposition to inflammatory bowel disease (IBD) has been shown by epidemiological and linkage studies. Genetic linkage of IBD to chromosome 16 has been previously observed and replicated in independent populations. The recently identified NOD2 gene is a good positional and functional candidate gene since it is located in the region of linkage on chromosome 16q12, and activates nuclear factor (NF) kappaB in response to bacterial lipopolysaccharides. Methods We sequenced the coding region of the NOD2 gene and genotyped an insertion polymorphism affecting the leucine-rich region of the protein product in 512 individuals with IBD from 309 German or British families, 369 German trios (ie, German patients with sporadic IBD and their unaffected parents), and 272 normal controls. We then tested for association with Crohns disease and ulcerative colitis. Findings Family-based association analyses were consistently positive in 95 British and 99 German affected sibling pairs with Crohns disease (combined p<0.0001); the association was confirmed in the 304 German trios with Crohns disease. No association was seen in the 115 sibling pairs and 65 trios with ulcerative colitis. The genotype-specific disease risks conferred by heterozygous and homozygous mutant genotypes were 2.6 (95% CI 1.5-4.5) and 42.1 (4.3-infinity), respectively. Interpretation The insertion mutation in the NOD2 gene confers a substantially increased susceptibility to Crohns disease but not to ulcerative colitis.

Sequence variants in IL10, ARPC2 and multiple other loci contribute to ulcerative colitis susceptibility

Inflammatory bowel disease (IBD) typically manifests as either ulcerative colitis (UC) or Crohns disease (CD). Systematic identification of susceptibility genes for IBD has thus far focused mainly on CD, and little is known about the genetic architecture of UC. Here we report a genome-wide association study with 440,794 SNPs genotyped in 1,167 individuals with UC and 777 healthy controls. Twenty of the most significantly associated SNPs were tested for replication in three independent European case-control panels comprising a total of 1,855 individuals with UC and 3,091 controls. Among the four consistently replicated markers, SNP rs3024505 immediately flanking the IL10 (interleukin 10) gene on chromosome 1q32.1 showed the most significant association in the combined verification samples (P = 1.35 × 10−12; OR = 1.46 (1.31–1.62)). The other markers were located in ARPC2 and in the HLA-BTNL2 region. Association between rs3024505 and CD (1,848 cases, 1,804 controls) was weak (P = 0.013; OR = 1.17 (1.01–1.34)). IL10 is an immunosuppressive cytokine that has long been proposed to influence IBD pathophysiology. Our findings strongly suggest that defective IL10 function is central to the pathogenesis of the UC subtype of IBD.

Genetic variation in DLG5 is associated with inflammatory bowel disease

Crohn disease and ulcerative colitis are two subphenotypes of inflammatory bowel disease (IBD), a complex disorder resulting from gene-environment interaction. We refined our previously defined linkage region for IBD on chromosome 10q23 and used positional cloning to identify genetic variants in DLG5 associated with IBD. DLG5 encodes a scaffolding protein involved in the maintenance of epithelial integrity. We identified two distinct haplotypes with a replicable distortion in transmission (P = 0.000023 and P = 0.004 for association with IBD, P = 0.00012 and P = 0.04 for association with Crohn disease). One of the risk-associated DLG5 haplotypes is distinguished from the common haplotype by a nonsynonymous single-nucleotide polymorphism 113G→A, resulting in the amino acid substitution R30Q in the DUF622 domain of DLG5. This mutation probably impedes scaffolding of DLG5. We stratified the study sample according to the presence of risk-associated CARD15 variants to study potential gene-gene interaction. We found a significant difference in association of the 113A DLG5 variant with Crohn disease in affected individuals carrying the risk-associated CARD15 alleles versus those carrying non-risk-associated CARD15 alleles. This is suggestive of a complex pattern of gene-gene interaction between DLG5 and CARD15, reflecting the complex nature of polygenic diseases. Further functional studies will evaluate the biological significance of DLG5 variants.

Association of FOXO3A variation with human longevity confirmed in German centenarians

The human forkhead box O3A gene (FOXO3A) encodes an evolutionarily conserved key regulator of the insulin–IGF1 signaling pathway that is known to influence metabolism and lifespan in model organisms. A recent study described 3 SNPs in the FOXO3A gene that were statistically significantly associated with longevity in a discovery sample of long-lived men of Japanese ancestry [Willcox et al. (2008) Proc Natl Acad Sci USA 105:13987–13992]. However, this finding required replication in an independent population. Here, we have investigated 16 known FOXO3A SNPs in an extensive collection of 1,762 German centenarians/nonagenarians and younger controls and provide evidence that polymorphisms in this gene were indeed associated with the ability to attain exceptional old age. The FOXO3A association was considerably stronger in centenarians than in nonagenarians, highlighting the importance of centenarians for genetic longevity research. Our study extended the initial finding observed in Japanese men to women and indicates that both genders were likely to be equally affected by variation in FOXO3A. Replication in a French centenarian sample generated a trend that supported the previous results. Our findings confirmed the initial discovery in the Japanese sample and indicate FOXO3A as a susceptibility gene for prolonged survival in humans.

Activation of nuclear factor κB in inflammatory bowel disease

Background—Expression of pro-inflammatory cytokines is increased in the intestinal lamina propria of patients with inflammatory bowel disease (IBD). Nuclear factor κB (NFκB) controls transcription of inflammation genes. On activation, NFκB is rapidly released from its cytoplasmic inhibitor (IκB), transmigrates into the nucleus, and binds to DNA response elements in gene promoter regions. Aims—To investigate whether increased activation of NFκB is important in IBD and may be down-regulated by anti-inflammatory treatment. Methods—Activation of NFκB was determined by western blot assessment and electrophoretic mobility shift assay in nuclear extracts of colonic biopsy samples as well as lamina propria mononuclear cells. Results—Nuclear levels of NFκB p65 are increased in lamina propria biopsy specimens from patients with Crohn’s disease in comparison with patients with ulcerative colitis and controls. Increased activation of NFκB was detected in lamina propria mononuclear cells from patients with active IBD. Corticosteroids strongly inhibit intestinal NFκB activation in IBD in vivo and in vitro by stabilising the cytosolic inhibitor IκBα against activation induced degradation. Conclusions—In both IBDs, but particularly Crohn’s disease, increased activation of NFκB may be involved in the regulation of the inflammatory response. Inhibition of NFκB activation may represent a mechanism by which steroids exert an anti-inflammatory effect in IBD.

Activation of nuclear factor kappa B inflammatory bowel disease.

Background—Expression of pro-inflammatory cytokines is increased in the intestinal lamina propria of patients with inflammatory bowel disease (IBD). Nuclear factor κB (NFκB) controls transcription of inflammation genes. On activation, NFκB is rapidly released from its cytoplasmic inhibitor (IκB), transmigrates into the nucleus, and binds to DNA response elements in gene promoter regions. Aims—To investigate whether increased activation of NFκB is important in IBD and may be down-regulated by anti-inflammatory treatment. Methods—Activation of NFκB was determined by western blot assessment and electrophoretic mobility shift assay in nuclear extracts of colonic biopsy samples as well as lamina propria mononuclear cells. Results—Nuclear levels of NFκB p65 are increased in lamina propria biopsy specimens from patients with Crohn’s disease in comparison with patients with ulcerative colitis and controls. Increased activation of NFκB was detected in lamina propria mononuclear cells from patients with active IBD. Corticosteroids strongly inhibit intestinal NFκB activation in IBD in vivo and in vitro by stabilising the cytosolic inhibitor IκBα against activation induced degradation. Conclusions—In both IBDs, but particularly Crohn’s disease, increased activation of NFκB may be involved in the regulation of the inflammatory response. Inhibition of NFκB activation may represent a mechanism by which steroids exert an anti-inflammatory effect in IBD.

Association of NOD2 (CARD 15) genotype with clinical course of Crohn's disease: a cohort study

BACKGROUND Crohns disease is a heterogeneous disorder for which NOD2 (CARD 15) has been identified as a susceptibility gene. We investigate the relation between NOD2 genotype and phenotypic characteristics of patients with Crohns disease. METHODS Hypotheses about the relation between NOD2 genotype and Crohns disease phenotype were generated retrospectively from a group of 446 German patients with this disorder. Positive findings (p<0.10) were verified in prospectively established cohorts of 106 German and 55 Norwegian patients with Crohns disease. All patients were genotyped for the main coding mutations in NOD2, denoted SNP8, SNP12, and SNP13, with Taqman technology. FINDINGS In the retrospective cohort, six clinical characteristics showed noteworthy haplotype association: fistulising, ileal, left colonic and right colonic disease, stenosis, and resection. In the German prospective cohort, these haplotype associations could be replicated for ileal (p=0.006) and right colonic disease (p < or =0.001). A similar trend was noted in the Norwegian patients. INTERPRETATION We recorded a distinct relation between NOD2 genotype and phenotype of Crohns disease. Test strategies with NOD2 variations to predict the clinical course of Crohns disease could lead to the development of new therapeutic paradigms.

Replication of signals from recent studies of Crohn's disease identifies previously unknown disease loci for ulcerative colitis

Following up on recent genome-wide association studies (GWAS) of Crohns disease, we investigated 50 previously reported susceptibility loci in a German sample of individuals with Crohns disease (n = 1,850) or ulcerative colitis (n = 1,103) and healthy controls (n = 1,817). Among these loci, we identified variants in 3p21.31, NKX2-3 and CCNY as susceptibility factors for both diseases, whereas variants in PTPN2, HERC2 and STAT3 were associated only with ulcerative colitis in our sample collection.

p38 Mitogen-Activated Protein Kinase Is Activated and Linked to TNF-α Signaling in Inflammatory Bowel Disease

Inflammatory bowel diseases (IBD)—Crohn’s disease and ulcerative colitis—are relapsing chronic inflammatory disorders which involve genetic, immunological, and environmental factors. The regulation of TNF-α, a key mediator in the inflammatory process in IBD, is interconnected with mitogen-activated protein kinase pathways. The aim of this study was to characterize the activity and expression of the four p38 subtypes (p38α–δ), c-Jun N-terminal kinases (JNKs), and the extracellular signal-regulated kinases (ERK)1/2 in the inflamed intestinal mucosa. Western blot analysis revealed that p38α, JNKs, and ERK1/2 were significantly activated in IBD, with p38α showing the most pronounced increase in kinase activity. Protein expression of p38 and JNK was only moderately altered in IBD patients compared with normal controls, whereas ERK1/2 protein was significantly down-regulated. Immunohistochemical analysis of inflamed mucosal biopsies localized the main expression of p38α to lamina propria macrophages and neutrophils. ELISA screening of the supernatants of Crohn’s disease mucosal biopsy cultures showed that incubation with the p38 inhibitor SB 203580 significantly reduced secretion of TNF-α. In vivo inhibition of TNF-α by a single infusion of anti-TNF-α Ab (infliximab) resulted in a highly significant transient increase of p38α activity during the first 48 h after infusion. A significant infliximab-dependent p38α activation was also observed in THP-1 myelomonocytic cells. In human monocytes, infliximab enhanced TNF-α gene expression, which could be inhibited by SB 203580. In conclusion, p38α signaling is involved in the pathophysiology of IBD.

PopGen: Population-Based Recruitment of Patients and Controls for the Analysis of Complex Genotype-Phenotype Relationships

Objective: Patient samples used for mapping complex human disease genes are unlikely to be representative of the phenotype spectrum of the respective population as a whole. On the other hand, most ongoing prospective studies are probably too small for evaluating polygenic disease markers. Design: Precise estimates of population-specific genotypic risks can be obtained efficiently through the complete ascertainment of patients in a geographically confined area. The PopGen project uses the most northern part of Germany as a target region for such a pursuit. Results: PopGen currently pursues recruitment, sampling and processing activities in close collaboration with a multitude of clinical partners, covering cardiovascular, neuropsychiatric and environmental diseases. Conclusion: PopGen has successfully established itself as a large-scale genetic epidemiological project of international recognition.