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Susanna Nikolaus

Publications and source records attributed to Susanna Nikolaus.

14 recordsLinked to original sources
PubMed2006

Evidence of transmission ratio distortion of DLG5 R30Q variant in general and implication of an association with Crohn disease in men.

Recently, we described the association of genetic variation in the discs large homolog 5 (DLG5) gene with inflammatory bowel disease (IBD) in a large European study sample (Stoll et al. in Nat Genet 36:476-480, 2004). Here, we report that the R30Q variant constitutes a susceptibility factor for Crohn disease (CD) in men [odds ratio (OR)=2.49, 95% confidence interval (CI) 1.53-4.06, P<0.001] but not women (OR=1.01, 95% CI=0.70-1.45, P=0.979) using multivariate logistic regression analyses in a unified study sample from Germany, Italy and Quebec. R30Q is a significant predictor for CD in men even when accounting for CARD15 and IBD5 risk variants (adjusted OR=2.41, 95% CI=1.41-4.12, P=0.001). The observed association is driven by a gender-dependent transmission ratio distortion (TRD) among healthy controls (frequency of Q allele: men 5.2%, women 11.3%), an effect that is offset in CD patients (frequency of Q allele: men 10.1%, women 10.9%). This finding is further substantiated by two non-IBD study samples, one of which consists of a newborn screening sample (newborn males 7.1%; newborn females 11%, P=0.036). Further investigation of the observed TRD may contribute towards enlightening the role of DLG5 in physiological processes influencing transmission of chromosomes to the surviving offspring, which, in turn, may help in understanding its implication in the development of CD among men.

Adult↗
PubMed2006

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.

Cardiovascular Diseases↗
PubMed2005

Sirtuin 1 (SIRT1) sequence variation is not associated with exceptional human longevity.

The SIR2/Sirt1 gene has been demonstrated as regulating lifespan in many model organisms, including yeast, Caenorhabditis elegans and rodents. These findings render the human homologue, SIRT1, a very plausible candidate as a modifier of human life expectancy. We therefore sought to investigate whether common allelic variation in the SIRT1 gene was associated with human longevity. Five single nucleotide polymorphisms (SNPs), distributed across the entire gene, including the promoter region, were genotyped in our extensive DNA collections of 1573 long-lived individuals (centenarians and nonagenarians) and matched younger controls. Four of the markers were haplotype-tagging SNPs (htSNPs) that defined five common haplotypes. No evidence for an association was detected between any of the tested SNPs and the longevity phenotype at the allele, genotype or haplotype levels. These findings, based on an htSNP approach, suggest that there is no noteworthy influence of SIRT1 sequence variation on exceptional human longevity in the German population. However, this does not rule out the possibility that allelic variants in direct regulators or downstream substrates of SIRT1 could play critical roles in extending lifespan in humans.

Aged↗
PubMed2005

Dissection of the inflammatory bowel disease transcriptome using genome-wide cDNA microarrays.

BACKGROUND: The differential pathophysiologic mechanisms that trigger and maintain the two forms of inflammatory bowel disease (IBD), Crohn disease (CD), and ulcerative colitis (UC) are only partially understood. cDNA microarrays can be used to decipher gene regulation events at a genome-wide level and to identify novel unknown genes that might be involved in perpetuating inflammatory disease progression. METHODS AND FINDINGS: High-density cDNA microarrays representing 33,792 UniGene clusters were prepared. Biopsies were taken from the sigmoid colon of normal controls (n = 11), CD patients (n = 10) and UC patients (n = 10). 33P-radiolabeled cDNA from purified poly(A)+ RNA extracted from biopsies (unpooled) was hybridized to the arrays. We identified 500 and 272 transcripts differentially regulated in CD and UC, respectively. Interesting hits were independently verified by real-time PCR in a second sample of 100 individuals, and immunohistochemistry was used for exemplary localization. The main findings point to novel molecules important in abnormal immune regulation and the highly disturbed cell biology of colonic epithelial cells in IBD pathogenesis, e.g., CYLD (cylindromatosis, turban tumor syndrome) and CDH11 (cadherin 11, type 2). By the nature of the array setup, many of the genes identified were to our knowledge previously uncharacterized, and prediction of the putative function of a subsection of these genes indicate that some could be involved in early events in disease pathophysiology. CONCLUSION: A comprehensive set of candidate genes not previously associated with IBD was revealed, which underlines the polygenic and complex nature of the disease. It points out substantial differences in pathophysiology between CD and UC. The multiple unknown genes identified may stimulate new research in the fields of barrier mechanisms and cell signalling in the context of IBD, and ultimately new therapeutic approaches.

Adolescent↗
PubMed2005

No association between microsomal triglyceride transfer protein (MTP) haplotype and longevity in humans.

Human longevity is a multifactorial condition with a significant genetic contribution. A recent association study in two independent samples of long-lived U.S. Caucasians [long-lived individuals (LLI)] identified a SNP haplotype of the microsomal triglyceride transfer protein (MTP, 4q25) that was underrepresented among LLI when compared with younger controls. This suggested that variation in the MTP gene might modify human longevity. Because of its function in lipid metabolism, the MTP gene product could plausibly play a pivotal role in the physiology of aging. However, the association observed in the U.S. samples could not be replicated by the same authors in a larger French LLI sample. We have therefore investigated the MTP "risk" haplotype in our own collection of 1,589 German nonagenarians, centenarians, and appropriately matched controls. No statistically significant differences were observed between LLI and controls at the allele, genotype, or haplotype level. This indicates that a noteworthy influence of the respective MTP haplotype on human longevity in the German population is unlikely. Furthermore, in comparison with all other U.S. and European samples analyzed, the MTP "risk" haplotype was found to be overrepresented only in the U.S. controls. This implies that the putative association is more likely to reflect recent changes in the genetic structure of the U.S. Caucasian population as a whole, rather than genetic effects upon survival to old age. In our view, the original study therefore highlights potential problems that arise when the case-control design is used as a means to map longevity genes in humans.

Aged↗
PubMed2004

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.

Alleles↗
PubMed2004

A comparison of oligonucleotide and cDNA-based microarray systems.

Large-scale public data mining will become more common as public release of microarray data sets becomes a corequisite for publication. Therefore, there is an urgent need to clarify whether data from different microarray platforms are comparable. To assess the compatibility of microarray data, results were compared from the two main types of high-throughput microarray expression technologies, namely, an oligonucleotide-based and a cDNA-based platform, using RNA obtained from complex tissue (human colonic mucosa) of five individuals. From 715 sequence-verified genes represented on both platforms, 64% of the genes matched in "present" or "absent" calls made by both platforms. Calls were influenced by spurious signals caused by Alu repeats in cDNA clones, clone annotation errors, or matched probes that were designed to different regions of the gene; however, these factors could not completely account for the level of call discordance observed. Expression levels in sequence-verified, platform-overlapping genes were not related, as demonstrated by weakly positive rank order correlation. This study demonstrates that there is only moderate overlap in the results from the two array systems. This fact should be carefully considered when performing large-scale analyses on data originating from different microarray platforms.

Aged↗
PubMed2003

Haplotype structure and association to Crohn's disease of CARD15 mutations in two ethnically divergent populations.

Current debate focuses on the relevance of linkage disequilibrium (LD), ethnicity and underlying haplotype structure to the search for genes involved in complex disorders. The recently described association between single nucleotide polymorphisms (SNPs) of the CARD15 (NOD2) gene and Crohn's disease (CD) in populations of north-European descent provides a test case that we have subjected to detailed SNP haplotype based analyses. We examined 23 SNPs spanning 290 kb, including CARD15, in large North-European and Korean samples of patients with Crohn's disease and normal controls. In Europeans we confirmed that the three disease-associated SNPs occur independently but share a common background haplotype. This suggests a common origin and the possibility of an undiscovered more strongly predisposing mutation. Korean CD patients present a phenotype identical to the European patients and have not previously been screened for CARD15. The three disease-associated SNPs were absent and there was no evidence of association between CARD15 and CD. Consequently, the disease-associated mutations in the Europeans, which are rare, have arisen recently (after the Asian-European split). Our results highlight important issues relevant to mapping the genes that predispose to complex disorders. First, although ethnically divergent populations may present identical phenotypes they do not necessarily share the same set of predisposing genes. Second, although single-locus tests of association showed consistent association with markers throughout the gene, pair-wise LD between markers (r(2) and D') yielded very little information about actual disease-association. Third, a population comparative approach allowed refining of the marker set through the examination of shared polymorphisms and common LD-groups. This approach, in conjunction with the examination of the mutational steps in a haplotype network, allows unambiguous identification of the potentially causative mutations.

Asian People↗
PubMed2002

p38 mitogen-activated protein kinase is activated and linked to TNF-alpha 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-alpha, 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 (p38alpha-delta), 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 p38alpha, JNKs, and ERK1/2 were significantly activated in IBD, with p38alpha 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 p38alpha 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-alpha. In vivo inhibition of TNF-alpha by a single infusion of anti-TNF-alpha Ab (infliximab) resulted in a highly significant transient increase of p38alpha activity during the first 48 h after infusion. A significant infliximab-dependent p38alpha activation was also observed in THP-1 myelomonocytic cells. In human monocytes, infliximab enhanced TNF-alpha gene expression, which could be inhibited by SB 203580. In conclusion, p38alpha signaling is involved in the pathophysiology of IBD.

Adult↗
PubMed2002

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

BACKGROUND: Crohn's 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 Crohn's disease. METHODS: Hypotheses about the relation between NOD2 genotype and Crohn's 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 Crohn's 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 Crohn's disease. Test strategies with NOD2 variations to predict the clinical course of Crohn's disease could lead to the development of new therapeutic paradigms.

Carrier Proteins↗
PubMed2002

Response to infliximab treatment in Crohn's disease is not associated with mutations in the CARD15 (NOD2) gene: an analysis in 534 patients from two multicenter, prospective GCP-level trials.

Infliximab induces remission in 30-40% of patients with active Crohn's disease. Treatment response is a stable trait over repeated doses yet the clinical predictors of response are still unknown. Recently, three variants in the CARD15 gene have been identified as major genetic risk factors for Crohn's disease. Single nucleotide polymorphisms (SNPs) 8, 12 and 13, have been shown to be independently associated with Crohn's disease susceptibility. The aim of the present study was to investigate these variants in relation to the therapeutic efficacy of infliximab. SNPs were genotyped (TaqMan) in two cohorts ( n= 90 and n= 444 (ACCENT I)) of active Crohn's disease patients (CDAI 220-450). The patients were recruited from independent multicenter trials conducted according to GCP. At the start of both trials, patients received a single infusion of open label infliximab (5 mg/kg bodyweight). The genotypic and allelic frequencies of each SNP were significantly associated with Crohn's disease in comparison to 370 healthy controls as reported previously. Response to infliximab (drop in CDAI 70 points or remission, respectively) was not associated with the genetic variants in the CARD15 gene in either cohort. The subsequent negative findings in a two-cohort model exclude SNPs 8, 12 and 13 of the CARD15 gene as predictors for therapeutic response to infliximab treatment.

Antibodies, Monoclonal↗