Association of NOD2 with Crohn's disease in a homogenous Irish population

NOD2 and Crohn's Disease Clinical Practice: From Epidemiology to Diagnosis and Therapy, Rewired

Crohn's disease (CD) is a chronic inflammatory bowel disease with a multifactorial pathogenesis involving environmental and genetic factors. Since the late 20th century, the discovery of the first susceptibility gene (NOD2, previously referred to as CARD15) for CD has paved the way for further investigations into the correlations between clinical features and genetics, and its potential impact on clinical practice has fueled the research in the last 2 decades. Recent therapeutic advancements involving novel biologic drugs and small molecules have shifted inflammatory bowel disease management from a disease-centered to a patient-centric approach. To date, the role of NOD2 has not been fully understood yet. Recent data suggest that its clinical impact may be greater than currently recognized. This review overviews the most common NOD2 variants' role in real-life clinical practice. These genetic variants increase the risk of developing the disease and can aid in tailoring diagnosis and treatment. They are associated with the stricturing phenotype and ileal involvement and increase the risk of steroid refractoriness. In the meantime, limited and inconclusive evidence exists regarding their predictive role in response to azathioprine, biologic drugs, and small molecules. Eventually, their role in increasing the risk for surgery is evident, especially in those with the L1007fs variant. If further trials will support the initial evidence reported so far, NOD2 genetic variants will emerge as possible candidates for developing precision medicine in CD.

Genetic Markers Associated with Clinical Outcomes in Patients with Inflammatory Bowel Disease

Genetic factors play a significant role in determining inflammatory bowel disease (IBD) susceptibility. Epidemiologic data support genetic contribution to the pathogenesis of IBD, which include familial aggregation, twin studies, and racial and ethnic differences in disease prevalence. Recently, several new genes have been identified to be involved in the genetic susceptibility to IBD. The characterization of novel genes potentially will lead to the identification of therapeutic agents and clinical assessment of phenotype and prognosis in patients with IBD. The development of genetic markers associated with clinical outcomes in patients with IBD will be very important in the future. The progress of molecular biology tools (microarrays, proteomics, and epigenetics) have progressed the field of the genetic markers discovery. The advances in bioinformatics coupled with cross-disciplinary collaborations have greatly enhanced our ability to retrieve, characterize, and analyze large amounts of data generated by the technological advances. The techniques available for markers development are genomics (single nucleotide polymorphism genotyping, pharmacogenetics, and gene expression analyses) and proteomics. This could be a potential great benefit in predicting the course of disease in individual patients and in guiding appropriate medical therapy.

NOD2/CARD15 and IL23R genetic variability in 204 Algerian Crohn's disease

NOD2/CARD15 and IL23R gene variants play an important role in the susceptibility to Crohn's disease (CD). Studies of genotype-phenotype relationship suggest that these variants are associated with the development of the disease and specific phenotype. Preliminary reports analyzing the association between these variants have never been made on Algerian CD's. In a case-control design, 204 Algerian with CD diagnosed for at least 5years and 201 controls were included were genotyped for single nucleotide polymorphisms (SNP) in the NOD2/CARD15 gene R702W (SNP8, rs2066844), G908R (SNP12, rs2066845) and IL23R R381Q (rs11209026) gene variants were determined using the TaqMan SNP genotyping assays. NOD2/CARD15 908R was carried by 3% of the patients and none in control subjects (χ(2)=8.6, Pc=0.003, OR=13.20). NOD2/CARD15 702W was associated to CD outcome (χ(2)=17.2, Pc=0.00003, OR=12.5) and early onset of disease (group A1, χ(2)=19.3, Pc=1.10(-5), OR=14.05, PM-H=2.10(-6)). IL23R 381Q variants was more frequent in CD's patients than controls (χ(2)=8, Pc=0.005, OR=3.48), it was associated to earlier onset (group A1, χ(2)=7.1, Pc=0.007, OR=1.04, PM-H=0.002), extra-intestinal manifestations (EIM) outcome (χ(2)=10.6, Pc=0.001, OR=1.05, PM-H=0.002) and ileocolonic location (χ(2)=6.8, Pc=0.009, OR=1.05, PM-H=0.001). In this Algerian cohort, NOD2/CARD15 and IL23R variants were associated with CD's outcomes and linked to a particular clinical phenotype.

Haplotype in the IBD5 region is associated with refractory Crohn's disease in Slovenian patients and modulates expression of the SLC22A5 gene

BACKGROUND

The IBD5 locus (OMIM ID 606348) on chromosome 5 was suggested to be one of the most important genetic factors involved in the pathogenesis of inflammatory bowel diseases (IBDs). However the main contributor from this region is still unknown.

METHODS

We investigated the possible association of the IBD5 locus with IBD in Slovenian patients and correlation between disease-associated single nucleotide polymorphisms (SNPs) and quantitative gene expression (eQTL) of candidate genes from the IBD5 locus in peripheral blood lymphocytes and colon tissue biopsies from IBD patients. We genotyped SNPs from the IBD5 locus in 312 healthy controls and 632 IBD patients.

RESULTS

We found statistically significant association of polymorphisms rs1050152 in gene SLC22A4 (p = 0.005, OR = 2.177, 95% CI = 1.270-3.526) and rs2631372 in gene SLC22A5 (p = 0.001, OR = 0.473, 95% CI = 0.307-0.731) and TC haplotype of both polymorphisms (p = 0.006, OR = 1,541, 95% CI = 1.130-2.100) with refractory Crohn's disease (CD) in Slovenian patients who do not respond to standard therapy, including patients who develop fistulas. We found decreased expression of SLC22A4 and SLC22A5 genes in peripheral blood lymphocytes from IBD patients compared to control group and decreased expression of SLC22A5 gene in inflamed tissue biopsies compared to noninflamed colon (p = 0.009). We found lower expression of SLC22A5 gene in IBD patients with disease-susceptible genotypes for both disease-associated SNPs.

CONCLUSIONS

Our data suggest that SNPs and haplotype in the IBD5 SLC22A4/SLC22A5 region contribute to the development of particularly refractory Crohn's disease in the Slovenian population, and expression studies in blood lymphocytes and colon tissue biopsies and eQTL analysis suggest that SLC22A5 is the main gene in the IBD5 region contributing to the IBD pathogenesis.

CTLA4 CT60 single-nucleotide polymorphism is associated with Slovenian inflammatory bowel disease patients and regulates expression of CTLA4 isoforms

We have evaluated functional polymorphism (rs3087243; in literature known also as CTLA4 CT60) in the cytotoxic T lymphocyte antigen 4 (CTLA4) gene, previously associated with several autoimmune diseases, for potential association with inflammatory bowel diseases (IBD). In addition, we investigated correlations between CTLA4 CT60 polymorphism and CTLA4 gene expression in peripheral blood lymphocytes and colon biopsies from IBD patients. We genotyped CTLA4 CT60 polymorphism in 266 healthy control subjects and 481 IBD patients and found statistically lower frequency of CTLA4 CT60 AA genotype in IBD patients (13.72%) compared to control subjects (23.31%; p = 0.001, odds ratio [OR] = 0.504) as well as lower allele frequency of minor A allele in IBD patients (0.346) compared to control subjects (0.461, p < 0.001, OR = 0.623). The association was confirmed with both major forms of IBD, Crohn's disease, and ulcerative colitis (UC), but was slightly stronger in UC patients, particularly when we compared allele frequency of A allele in UC patients (0.299) and control subjects (0.461, p < 0.001, OR = 0.500). We found lower expression of the CTLA4 gene in blood lymphocytes from IBD patients compared to control subjects (p < 0.001) and higher CTLA4 expression in biopsies taken from inflamed part of the colon compared to noninflamed part of the colon (p = 0.021). We found lower expression of soluble CTLA4 isoform than membrane-bound full-length isoform in peripheral blood lymphocytes from IBD patients compared to control subjects (p = 0.010) and in lymphocytes from IBD patients with CTLA4 CT60 GG genotype compared to IBD patients with AA genotype (p = 0.034). Our genotype and gene expression data suggest that CTLA4 plays a role in IBD pathogenesis. Polymorphism CTLA4 CT60 contributes to genetic susceptibility to IBD in Slovenian population and regulates expression of CTLA4 isoforms.

Combined polymorphisms in genes encoding the inflammasome components NALP3 and CARD8 confer susceptibility to Crohn's disease in Swedish men

OBJECTIVES

Crohn's disease (CD) is characterized by overproduction of proinflammatory cytokines like interleukin (IL)-1beta. Production of mature IL-1beta is dependent on a caspase-1-activating protein complex called the NALP3 inflammasome, composed of NALP3, ASC, and CARD8. NALP3 shares structural similarities with Nod2, and both of these proteins are required for bacteria-induced IL-1beta secretion. The combination of the polymorphisms CARD8 (C10X)and NALP3 (Q705K) was recently shown to be associated with rheumatoid arthritis.Our aim was to investigate whether these combined polymorphisms play a role in the susceptibility to CD.

METHODS

The study included 498 CD patients in two cohorts from different regions and 742 control individuals from a Swedish population. DNA was isolated from whole blood. Polymorphisms of (Q705K) NALP3 and (C10X) CARD8, as well as the Nod2 variants, R702W and G908R, were genotyped using the Taqman single nucleotide polymorphism assay. The Nod2 frameshift mutation, L1007fs, was detected by Megabace SNuPe genotyping.

RESULTS

Our results show that men who have both the C10X and Q705K alleles in CARD8 and NALP3, and who express wild-type alleles of Nod2 are at an increased risk of developing CD (odds ratio, OR: 3.40 range: 1.32-8.76); P = 0.011). No association with these polymorphisms was found in women (OR: 0.89 (range: 0.44-1.77); P = 0.74).

CONCLUSIONS

We suggest a role for combined polymorphisms in CARD8 and NALP3 in the development of CD in men, with obvious sex differences in the genetic susceptibility pattern. These findings give further support to the importance of innate immune responses in CD.

Extreme heterogeneity in CARD15 and DLG5 Crohn disease-associated polymorphisms between German and Norwegian populations

The first gene associated with Crohn disease (CD) has been identified as CARD15 (16q12). Three variants, R702W, G908R and 1007fsinsC are strongly and independently associated with the disease. A second gene, conveying a smaller risk for inflammatory bowel disease (IBD), has been identified as DLG5 (10q23). We assess the frequency of the CARD15 SNPs and of the R30Q mutation in DLG5 and their contribution to the development of CD in a cohort of unrelated IBD patients (151 CD, 325 ulcerative colitis (UC)) and healthy controls (236) from South-east Norway (IBSEN cohort). Genotype-based tests of population differentiation using 23 SNPs across CARD15, together with estimates of F(ST), indicated that the German and Norwegian background populations could be differentiated at the CARD15 locus. The Norwegian and German CD samples exhibited particularly strong differentiation at the three predisposing loci and those marking their background haplotype. There were significantly lower frequencies of the CARD15 SNPs and no significant association with CD in the Norwegian samples. Only a marginal association was observed for the subphenotypes ileitis and ileocolitis vs colitis (P=0.048). The population attributable risk percentage (PAR%) for CARD15 variants in the Norwegian cohort is the lowest reported for a European population (1.88%), except Iceland. Similarly, the DLG5 variant showed no association with CD or IBD, however, there was a negative correlation with stricture (P=0.035). The present results are consistent with an emerging pattern of a low frequency of the CARD15 variants in Northern countries where the prevalence of IBD is greatest.

Interactions among genes influencing bacterial recognition increase IBD risk in a population-based New Zealand cohort

Bacterial sensing is crucial for appropriate response by the innate and adaptive immune system against invading microorganisms. Single nucleotide polymorphisms (SNPs) in genes involved in bacterial recognition, CARD15 and TLR4, increased the risk of inflammatory bowel disease (IBD) in a New Zealand Caucasian case-control cohort. We now consider the effects of SNPs in CD14, TLR9, and BPI, analyzed individually, in association with one another, and with SNPs in CARD15 or TLR4 in this same population group. SNPs in CD14 (c.-159 C>T), TLR9 (c.-1237T>C) and BPI (c.645A>G) showed no significant allele or genotype frequency differences between IBD cases and controls. Genotype-phenotype mapping reveals an association with BPI and ileocolonic Crohn's disease (CD) as well as an association with CD14 and early-onset ulcerative colitis (UC). Genotype interaction analyses using three different statistical approaches provided significant evidence of interaction for the following combinations: CARD15/TLR4 (CD and UC), CARD15/CD14 (CD and UC), CD14/TLR4 (UC only), and CD14/BPI (UC only). A trend for an association between BPI and TLR4 was observed in UC patients, but failed to reach statistical significance. Our findings support the idea of gene-gene interactions for genes involved in closely related pathways (i.e. bacterial detection). There is evidence that carrying two SNPs in genes may lead to statistical significance for genes and SNPs that do not otherwise confirm as risk alleles for disease aetiology when analysed alone.

Disease behavior in children with Crohn's disease: the effect of disease duration, ethnicity, genotype, and phenotype

BACKGROUND

Disease behavior in Crohn's disease (CD) may be modified by disease location and genotype. Disease behavior may change over time, and thus analysis requires follow-up. To date, there have been few pediatric studies that have evaluated the association between disease behavior and genotype with prolonged follow-up. The aim of our study was to evaluate the effect of genotype, phenotype, and ethnicity on disease behavior in pediatric CD.

METHODS

Evaluation of 128 pediatric CD was followed by analysis of 232 pediatric and adult-onset CD patients. Inclusion required at least 2 years of follow-up. Phenotype, ethnicity, and disease duration were recorded. Patients were genotyped for polymorphisms in the NOD2/CARD15 gene.

RESULTS

Colonic involvement was more frequent in younger patients. Pediatric disease at end of follow-up was classified as inflammatory (78%), penetrating (7%), and stricturing (17%). Duration of follow-up (mean 4.9 pediatric and 6.4 years mixed) was associated with more stricturing and penetrating disease. There was no association between mean age of onset and NOD2/CARD15, or either of these with disease behavior. These observations were replicated in the mixed cohort. Sephardic Jewish origin was inversely correlated with inflammatory behavior (P = 0.006), independent of NOD2/CARD15 genotype.

CONCLUSIONS

Duration of disease and ethnicity, irrespective of NOD2/CARD15 genotype and age of onset, were the only predictors for penetrating or stricturing disease.

CARD15 gene polymorphisms in Serbian patients with Crohn's disease: genotype-phenotype analysis

OBJECTIVE

Genetic heterogeneity and incomplete phenotype penetrance complicate genetic analysis of Crohn's disease (CD). Studies in western Europe have shown that CARD15 polymorphisms increase susceptibility to CD, but frequencies vary within different European populations. The aim here was to evaluate the prevalence of CARD15 mutations and their phenotypic correlation in a Serbian population.

MATERIALS AND METHODS

131 patients with CD, 65 patients with ulcerative colitis, and 88 healthy controls were genotyped for three common mutations (R702W, G908R, Leu1007insC) by PCR-restriction fragment length polymorphism. chi and Student's t-test were used for statistical assessment.

RESULTS

At least one CARD15 disease-associated allele was found in 35.11% patients with CD, 14.77% of healthy controls (P=0.001), and 7.69% patients with ulcerative colitis (P=0.0001). The L1007fs mutation showed a significant association with CD (P<0.0001). The frequency of R702W mutant allele was almost equal in the control group and CD patients Univariate analyses established that CARD15 carriers had a significantly higher risk of isolated ileal location [P=0.042; odds ratio (OR) 2.30; 95% confidence interval (CI): 1.02-5.19], fibrostenotic behavior (P<0.0001; OR 9.86; 95% CI: 4.29-22.62), surgical resection (P=0.036; OR 2.2; CI, 1.046-4.626), and earlier onset of disease (P=0.026).

CONCLUSION

This study confirms that CARD15 carriers, especially L1007fs mutants, in central Europeans have an increased risk of CD and it is associated with earlier onset, ileal, fibrostenotic disease and a higher risk of surgery. Any influence of latitude is not matched by an east-west divide on the genotype frequency and phenotype of CD within Europe.

Polymorphisms of CARD15/NOD2 and CD14 genes in New Zealand Crohn's disease patients

Polymorphisms in the CARD15/NOD2 gene, which encodes a cytosolic protein involved in bacterial recognition, are associated with development of Crohn's disease (CD). Other potential susceptibility genes such as CD14 may compound the risk of developing CD. We examined the frequency of the three major CARD15 risk alleles (3020insC/L1007fsinsC, G908R and R702W), and a functional polymorphism (-159C/T) in the promoter of the CD14 gene in 185 CD patients in New Zealand and 187 ethnically matched controls. The frequencies of the 3020insC (8.1 vs 0.8%, P < 0.0001), G908R (3.5 vs 2.4%, P = 0.37) and R702W (7.3 vs 5.1%, P = 0.21) alleles in CD patients and controls, respectively, were similar to those described in Australia, and the ancestral countries of Scotland, Ireland and the UK. Only the 3020insC polymorphism was found to be a significant risk factor for CD in our New Zealand cohort (odds ratio = 10.91 [95% confidence intervals 3.30-36.08]; P < 0.0001 for heterozygotes), but not a single patient was homozygous for the 3020insC polymorphism. The T allele (51 vs 50%, P = 0.77) and TT genotype (26 vs 24%, P = 0.84) frequencies of the -159C/T CD14 gene promoter polymorphism did not significantly differ between CD patients and controls. In summary, our findings provide evidence that the CARD15 3020insC risk allele influences disease susceptibility in a small proportion (<17%) of New Zealand CD patients, whereas there was no evidence that the CD14 -159C/T polymorphism is associated with CD.

Mutations in CARD15 and smoking confer susceptibility to Crohn's disease in the Danish population

OBJECTIVE

Three CAspase Recruitment Domain (CARD15) mutations have shown to predispose to Crohn's disease in Caucasian populations. The aim of this study was to investigate the mutation frequency in patients with inflammatory bowel disease and in healthy controls in Denmark.

MATERIAL AND METHODS

Genotyping of the three common CARD15 mutations was carried out on 388 patients with Crohn's disease, 565 patients with ulcerative colitis and 796 healthy controls using real-time PCR. Allele and genotype frequencies in the three groups were compared. A possible additive effect of smoking on CARD15 mutations was also examined.

RESULTS

Carrying at least one CARD15 mutation was significantly more common in patients with Crohn's disease compared with healthy controls (21% versus 10%; p <0.001). A gene-dosage effect was observed (ORadj.smoking 22.2; p <0.001 for carrying two CARD15 mutations versus ORadj.smoking 1.8; p=0.01 for carrying one CARD15 mutation). The 1007insC protein truncating mutation was the major contributing mutation. Ileal involvement was more common in Crohn's disease patients with CARD15 mutations as opposed to patients without CARD15 mutations (ORadj.smoking 3.6; p <0.001). Smoking was independently associated with Crohn's disease (OR 1.8; p <0.001), but no multiplicative effect of smoking on CARD15 genotypes was found.

CONCLUSIONS

In the Danish population, CARD15 mutations were found to be associated with Crohn's disease, hence supporting the hypothesis of a genetic component contributing to the disease. Further research for other genes possibly involved in Crohn's disease may result in the use of genetic testing for diagnosis or treatment of Crohn's disease in the future.

TLR2, TLR4 and TLR9 polymorphisms and Crohn's disease in a New Zealand Caucasian cohort

BACKGROUND AND AIM

Toll-like receptors (TLRs) have been identified as susceptibility genes for Crohn's disease (CD) in some, but not all, studies. Here we examined the association between candidate disease-susceptibility polymorphisms in the TLR2, TLR4 and TLR9 genes and CD in a New Zealand Caucasian population.

METHODS

The frequency of gene polymorphisms was examined in 182 CD patients and in 188 ethnically matched controls by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis.

RESULTS

We could not detect any significant difference in the allele frequencies of polymorphisms in the TLR2 (R753Q, 0.029 vs 0.016, P = 0.25), TLR4 (D299G and T399I, 0.085 vs 0.071, P = 0.49; and 0.085 vs 0.082, P = 0.90), and TLR9 (-1237T/C, 0.154 vs 0.148, P = 0.82) genes between controls and patients, respectively. There was no evidence that the variant TLR alleles were associated with disease phenotype. However, combination of the datasets of published studies with our dataset confirmed that the TLR4 polymorphism 299G (P = 0.0005; OR of 1.42 [95% CI 1.17-1.74]) and the TLR9 polymorphism -1237C (P = 0.0416; OR of 1.33 [95% CI 1.01-1.75]) are associated with CD.

CONCLUSIONS

There was no evidence that the above variants of the TLR2, TLR4 and TLR9 genes are major risk factors for CD or influence disease phenotype in our New Zealand case-control study. Nevertheless, the significance of the TLR4 299G and TLR9-1237C associations with CD worldwide was confirmed by a meta-analysis test using our datasets and datasets from previously published studies.

Effect of inflammatory bowel disease classification changes on NOD2 genotype-phenotype associations in a population-based cohort

BACKGROUND

NOD2 mutations are associated with Crohn's disease (CD) in Caucasian clinic-based cohorts. Data from population-based cohorts are limited. Clinic-based studies may overestimate this association. Genotype-phenotype relationships are yet to be assessed using the Montreal classification. We hypothesized that the NOD2-CD association would be weaker in a population-based cohort, and that the Montreal classification would strengthen genotype-phenotype associations.

METHODS

A population-based case-control study was performed including 91% of all people in Canterbury, New Zealand, with inflammatory bowel disease (IBD); NOD2 genotyping was performed and patients were phenotyped according to the Vienna and Montreal classification systems.

RESULTS

The NOD2 genotype was available on 684 CD, 643 ulcerative colitis (UC), 36 indeterminate colitis/IBDU (IBD unclassified) patients, and 201 controls. Control frequencies for the 702W, 908R, and 1007fs alleles were 0.030, 0.012, and 0.010, respectively, compared with 0.074, 0.027, and 0.040 for CD. The 702W (P = 0.001) and 1007fs (P = 0.002) alleles were significantly associated with CD. Younger age of diagnosis (<17 years) was associated with 1 (odds ratio (OR) 1.9 [95% confidence intervals 0.98-3.6]) or 2 (OR 6.5 [2.3-18.6]) NOD2 mutations compared with diagnosis >40 years. Ileal disease was most strongly associated with NOD2 mutations (1 mutation OR 3.9 [2.4-6.3], 2 mutations OR 6.7 [2.4-18.5]). Penetrating disease was associated with NOD2 mutations using the Montreal but not the Vienna classification.

CONCLUSIONS

The association between NOD2 mutations and CD was found to be weaker in our population-based cohort than in previous studies that used referral-based cohorts. Application of the Montreal classification led to a strengthening of the NOD2 genotype-phenotype association.

Prevalence of CARD15/NOD2 mutations in Caucasian healthy people

BACKGROUND

Crohn's disease (CD) has been associated with CARD15/NOD2 mutations in Caucasians. The R702W, G908R, and 1007fs mutations represent 82% of the mutated chromosomes. The relative risk of developing CD in homozygous or compound heterozygous people has been estimated as between 10 and 40 times that of the general population. This high risk may support the opinion that CARD15/NOD2 variants are strong CD risk factors at the individual and population levels.

SUBJECTS AND METHODS

The allele and genotype frequencies were calculated for the R702W, G908R, and 1007fs mutations in 3,575 Caucasian healthy controls recruited by 15 groups distributed on three continents. Geographic homogeneity was tested and the observed proportion of double mutants was compared with the expected value using chi2 tests.

RESULTS

The allele frequencies of the R702W, G908R, and 1007fs mutations were 4.3% (3.6-4.9), 1.2% (0.8-1.6), and 2.3% (1.8-2.8), respectively, with large geographic fluctuations of the G908R, 1007fs, and wild-type alleles (P<0.0001). At the population level, no simple relationship was observed between mutation frequencies and the disease incidences in the studied populations. At the individual level, no significant deficit of double-dose mutation carriers among healthy controls was found, providing strong evidence that the penetrances of the most at-risk genotypes are low.

CONCLUSION

Altogether, these data confirm that CARD15/NOD2 acts in interaction with other unknown risk cofactors.

CARD15 mutations in Dutch familial and sporadic inflammatory bowel disease and an overview of European studies

OBJECTIVES

The single nucleotide variations R702W, G908R and L1007fs in the CARD15 gene have been found to be independently associated with Crohn's disease. The aim of this study was to evaluate the prevalence of these gene variations in Dutch multiple inflammatory bowel disease-affected families, in sporadic inflammatory bowel disease patients and in healthy controls.

METHODS

Dutch Caucasians from multiple inflammatory bowel disease-affected families were recruited, including 78 probands with Crohn's disease, 34 probands with ulcerative colitis and 71 inflammatory bowel disease-affected and 100 non-affected family members. In addition, 45 sporadic inflammatory bowel disease patients (36 Crohn's disease and nine ulcerative colitis), and 77 unrelated healthy controls were included. Genomic DNA was isolated to determine CARD15 R702W, G908R and L1007fs. For these mutations, we evaluated disease susceptibility and correlation with inflammatory bowel disease phenotypes.

RESULTS

In all included unrelated inflammatory bowel disease-affected probands, the R702W, G908R and L1007fs allele frequencies were 8.8, 6.1 and 11.0%, respectively, for Crohn's disease, and 4.7, 0 and 2.3% for ulcerative colitis. In controls, the allele frequencies were 5.9, 0.7 and 1.9%, respectively. G908R and L1007fs were associated with Crohn's disease (P=0.006 and 0.001, respectively). Compound heterozygotes for any of the three mutations were 11 (9.2%) in Crohn's disease patients, but none in ulcerative colitis patients nor controls. Carriage of CARD15 mutations was not associated with familial disease (P>or=0.38). Inflammatory bowel disease-affected family members of Crohn's disease probands carrying L1007fs, however, were carriers significantly more often than expected (P<0.001). In Crohn's disease patients, a significant trend was found between carriage of at least one CARD15 mutation and between carriage of L1007fs and behaviour of disease, including more carriers with stricturing and even more with penetrating disease (P=0.006 and 0.017, respectively).

CONCLUSION

In the Dutch population, CARD15 G908R and L1007fs are associated with Crohn's disease. Although no difference was found between sporadic and familial cases, in L1007fs-positive multiple affected families the inflammatory bowel disease-affected relatives are more likely than expected to carry this mutation. In Crohn's disease, carriage of at least one CARD15 mutation is associated with a more complicated disease behaviour.

Inflammatory bowel disease genetics: Nod2

The inflammatory bowel diseases (IBD) are comprised of two major subphenotypes, Crohn's disease (CD) and ulcerative colitis (UC). A significant role for genetic factors in IBD was established from epidemiologic studies and, more recently, the identification of well-established disease associations, notably the association of Nod2 (CARD15) polymorphisms with CD. The mapping to CD of Nod2 variants that alter protein function represents one of the earliest, most well-established, associations in complex genetic disorders. Since the initial discovery, genotype-phenotype correlations, definition of Nod2 expression and signaling pathways, association studies in other, related disorders, and features of Nod2 deficiency in murine models have been reported. Taken together, the Nod2 association to CD provides an illustrative model of the role of single gene variants in disease pathogenesis for common, complex multigenic disorders. Here we review general aspects of IBD genetics with particular focus on the role of Nod2 in CD.

Genetics of the innate immune response in inflammatory bowel disease

The discovery of nucleotide-binding oligomerization domain 2/caspase recruitment domain-containing protein 15 (NOD2/CARD15) as the first susceptibility gene in Crohn's disease (CD) has shifted the focus of research into the pathogenesis of inflammatory bowel disease (IBD) firmly to the innate immune response and the integrity of the epithelial barrier. The subsequent implication in IBD of variant alleles of OCTN, DLG5, MDR1, and TLRs has provided further support for a new, more complex model of innate immunity function in the gastrointestinal tract. In this review, we examine the recent advances in our understanding of the influence of genetics of the innate immune response on IBD. We will focus on germline variation of genes encoding pathogen-recognition receptors, proteins involved in epithelial homeostasis and secreted antimicrobial proteins.

Gut microbiota: mining for therapeutic potential

The resident microbiota of the human intestine exerts a conditioning effect on intestinal homeostasis, delivering regulatory signals to the epithelium and instructing mucosal immune responses. Pattern recognition receptors are key mediators of innate host defense, and in healthy individuals, the mucosal immune system exhibits an exquisitely regulated restrained response to the resident microbiota. However, in genetically susceptible hosts, unrestrained mucosal immune activation in response to local bacterial signals can contribute to the pathogenesis of inflammatory bowel disease. Manipulation of the microbiota to enhance its beneficial components thus represents a potential therapeutic strategy for inflammatory bowel disease. Moreover, the microbiota might be a rich repository of metabolites that can be exploited for therapeutic benefit. Modern molecular techniques are facilitating improved understanding of host-microbe dialogue in health and in several disease processes, including inflammatory bowel disease. It follows that elucidating the molecular mechanisms of host-microbial interactions is now a prerequisite for a "bugs to drugs" program of discovery.

Pediatric Crohn disease: clinical and genetic characteristics in Taiwan

OBJECTIVES

Crohn disease (CD) is a heterogeneous disorder. The nucleotide oligomerization domain 2/caspase activating recruitment domain 15 (NOD2/CARD15) gene located at 16q12 is strongly associated with susceptibility to CD in white people but is absent in adult Asian patients, whereas the role of Toll-like receptor 4 (TLR4) polymorphisms has also been reported. Because clinical and genetic data in Asian children with CD are lacking, the aim of this study was to elucidate the clinical and genetic characteristics of Taiwanese children with CD.

PATIENTS AND METHODS

All of the children hospitalized at the National Taiwan University Hospital between January 2000 and July 2005 who fulfilled the diagnostic criteria for CD were enrolled. Their clinical characteristics were recorded, and genomic DNA was extracted from their white blood cells. After polymerase chain reaction was performed, direct sequencing was done to detect the 4 NOD2 hotspot mutations (P268S, R702W, G908R, 1007fs) and TLR4 polymorphisms (Asp299Gly, Thr399Ile).

RESULTS

CD was diagnosed in 10 children (6 boys and 4 girls; age range at diagnosis, 14 months to 13 years; median age, 11.1 years). There were 5 children with ileocolonic region involvement, 3 with colonic region involvement, 2 with ileal region involvement, 4 with additional upper gastrointestinal tract involvement, and 2 with additional perianal fistula. Half of the children had growth retardation at diagnosis. Neither NOD2/CARD15 mutations nor TLR4 polymorphisms were found in the 10 patients.

CONCLUSIONS

Ileocolonic location and inflammatory behavior constitute the most frequent phenotype of CD in Taiwan. Mutations in the NOD2/CARD15 and TLR4 genes that are common in the West are not associated with CD in Taiwanese children.

Review article: genetic susceptibility and application of genetic testing in clinical management of inflammatory bowel disease

The volume of research undertaken on the genetic susceptibility of inflammatory bowel disease (IBD) has been tremendous, and over 10 chromosomal regions have been identified by genome-wide scanning. Fine-mapping approaches and candidate gene studies have already led to the identification of several susceptibility genes, including CARD15 (NOD2), DLG5, novel organic cation transporter (OCTN) 1 and 2, and CARD4 (NOD1). The CARD15 gene is the most understood at present and explains around 20% of the genetic predisposition to Crohn's disease. Although the clinical implications of genetic testing are limited at present, genetic research has advanced our understanding of the clinical heterogeneity and the complex interactions between genetic and environmental risk factors in IBD. Genes also interfere with the metabolism of drugs and may influence the clinical response and drug-related toxicity. Ultimately, researchers and clinicians aim to personalize medicine based on a patient's genotype, although azathioprine (thiopurine methyltransferase polymorphisms) is the only drug to date where pharmacogenetics has shown clinical relevance in IBD. In the future, it is anticipated that genetic markers will be implemented in an integrated molecular diagnostic and prognostic approach to managing our patients.

TUCAN (CARD8) genetic variants and inflammatory bowel disease

BACKGROUND & AIMS

The identification of the association between Crohn's disease (CD) and NOD2 (CARD15) confirmed both the heritability of CD and highlighted the role of the nuclear factor kappaB (NFkappaB) pathway in disease pathogenesis. Other susceptibility loci exist. TUCAN (CARD8) is located beneath a CD peak of linkage on chromosome 19q. TUCAN is expressed in the gut and is a negative regulator of NFkappaB, making it an excellent candidate gene for gastrointestinal inflammation.

METHODS

Ten single nucleotide polymorphisms (SNP) across TUCAN were genotyped in 365 controls, 372 patients with CD, and 373 patients with ulcerative colitis. A diagnostic panel for CD was constructed using smoking status and TUCAN, NOD2, IBD5, NOD1, and TNFSF15 data.

RESULTS

We demonstrate significant association between a TUCAN SNP and CD (OR 1.35, P = .0083). The association was more pronounced with disease affecting sites other than the colon (odds ratio, 1.52) and NOD2-negative CD (odds ratio, 1.50). Combination of these data with smoking and NOD2, IBD5, NOD1, and TNFSF15 status demonstrated very strong associations with CD and high sensitivities (96.3%), specificities (99.4%), and likelihood ratios (12.8) for CD, although further work will be needed before this model can be translated into direct clinical utility.

CONCLUSIONS

We have shown an association between a likely functional polymorphism in TUCAN and CD. The combination of these data in a genetic panel suggests that clinicians may soon be able to translate genetic advances into direct benefits for patients.

The gut flora as a forgotten organ

The intestinal microflora is a positive health asset that crucially influences the normal structural and functional development of the mucosal immune system. Mucosal immune responses to resident intestinal microflora require precise control and an immunosensory capacity for distinguishing commensal from pathogenic bacteria. In genetically susceptible individuals, some components of the flora can become a liability and contribute to the pathogenesis of various intestinal disorders, including inflammatory bowel diseases. It follows that manipulation of the flora to enhance the beneficial components represents a promising therapeutic strategy. The flora has a collective metabolic activity equal to a virtual organ within an organ, and the mechanisms underlying the conditioning influence of the bacteria on mucosal homeostasis and immune responses are beginning to be unravelled. An improved understanding of this hidden organ will reveal secrets that are relevant to human health and to several infectious, inflammatory and neoplastic disease processes.

NOD2/CARD15 mutations in Croatian patients with Crohn's disease: prevalence and genotype-phenotype relationship

BACKGROUND

Crohn's disease (CD) is a chronic inflammatory disorder of the gastrointestinal tract with variations in localization and behaviour. Mutations in the NOD2/CARD15 gene on chromosome 16q have been implicated in the pathogenesis of the disease and three main sequence variants, all single nucleotide polymorphisms (SNPs), have been identified in North American and European populations.

AIMS AND METHODS

As no data exist in the Croatian population, we consecutively collected a cohort of 136 CD patients and 91 healthy controls to determine the prevalence of NOD2/CARD15 mutations and their association with phenotypic expression of the disease. All patients and controls were genotyped for Arg702Trp (Hugot SNP8), Gly908Arg (Hugot SNP12), and Leu1007fsinsC (Hugot SNP13) and allele frequencies were compared between the Crohn's patients and controls. The correlation of NOD2/CARD15 genotypes with the phenotypic expression of Crohn's disease was further assessed by logistic regression analysis.

RESULTS

NOD2/CARD15 variants were found in 38/136 CD patients (27.9%) compared to 10/91 (10.9%) healthy controls (P = 0.0022). Allele frequencies in patients with CD were 13.97%, 4.4% and 11.76%, respectively, for SNP8, 12 and 13, compared to 5.49%, 1.12% and 4.40% in controls (P = 0.041, P = 0.162, P = 0.055). Six CD patients carried double mutations and, remarkably, we identified two homozygous mutants amongst the healthy control group. Surgery over the course of the disease and a younger age at onset of the disease were significantly more frequent in patients who were carriers of NOD2/CARD15 mutations.

CONCLUSIONS

This report on NOD2/CARD15 mutations in Croatian patients with CD demonstrates that this gene is also implicated in susceptibility to CD in the Croatian population. Phenotypic association showed a younger age at diagnosis and a higher need for surgery in patients carrying NOD2/CARD15 mutations. However, the prevalence is somewhat lower compared to other reports, likely due to a more prominent colonic inflammation.

Contribution of CARD15 variants in determining susceptibility to Crohn's disease in Sweden

OBJECTIVE

Crohn's disease (CD) is a chronic inflammatory bowel disorder caused by environmental and genetic factors. Mutations in the CARD15 gene have been associated with CD. No previous case-control CARD15 study has been performed in the Swedish population.

MATERIAL AND METHODS

The study comprised of 321 individuals: 178 with CD and 143 healthy controls (HCs), all from Stockholm County. All were genotyped for the three main CD-associated CARD15 variants (R702W, G908R and 1007fs) and phenotypic associations were investigated.

RESULTS

The allele frequencies of the R702W variant (4.5% CD versus 0.7% HC, p=0.008, OR = 6.8) and the G908R variant (2.0% CD versus 0% HC, p=0.045) were more common in CD patients than in controls. No significant difference in1007fs variant allele frequency was found between CD patients and controls (2.0% CD versus 1.7% HC, p = 0.8, OR = 1.1). Carriage of CARD15 variants was more common in the CD patients than in controls (15.2% CD versus 4.2% HC, p = 0.001, OR = 4.1, population attributable risk (PAR) = 11.4%). Genotype-phenotype analysis demonstrated that CARD15 variants were associated with ileal disease (p=0.0006, OR = 9.3, CI = 2.2-34) and protective for colonic CD (p = 0.01, OR = 0.18). An association between CARD15 variants and ileal CD (p=0.004, OR = 6.6) was confirmed by multivariate analyses.

CONCLUSIONS

The CARD15 variants R702W and G908R, but not 1007fs, are associated with susceptibility to CD in Stockholm County. Genotype-phenotype analysis shows an association with ileal CD. The contribution of these CARD15 mutations in Swedish CD patients overall is low in relation to studies elsewhere in Central Europe and North America, but is consistent with emerging data from elsewhere in Scandinavia and in Northern Europe.

Advances in the molecular dissection of inflammatory bowel disease

Recent advances in the field of inflammatory bowel disease (IBD) genetics have enabled the definition and refinement of multiple IBD susceptibility loci and the identification of gene variants within such regions showing association with Crohn's disease (CD) and/or ulcerative colitis (UC). Most notable among the newly defined genetic determinants of IBD are specific variants in the CARD15 gene, which have been shown widely to influence both susceptibility and phenotype in CD. These genetic data have inspired intensive studies of CARD15 biologic functions and the information emerging from these analyses has already substantively enhanced understanding of the signaling pathways coupling bacterial pathogens to the host immune response. Genetic data implicating various other signaling effectors in IBD susceptibility have similarly focused attention on the molecular pathways driven or regulated by these proteins and the biochemical events linking effector/pathway dysfunction to intestinal inflammation and disease. In this review, progress in defining the genetic determinants of IBD is described with an emphasis on the impact of such knowledge on understanding of IBD molecular pathophysiology.

The role of inflammatory bowel disease susceptibility loci in multiple sclerosis and systemic lupus erythematosus

To date, three loci have been validated to confer susceptibility to inflammatory bowel disease (IBD): the CARD15/NOD2 gene, the discs large homolog 5 gene (DLG5), and the IBD5 locus on 5q31 (IBD5). We have explored the possibility that these loci may also be associated with susceptibility to two other chronic inflammatory diseases, multiple sclerosis (MS) and systemic lupus erythematosus (SLE). As the CARD15 risk alleles had previously been assessed in our collection of 496 MS trios, we focused our efforts on the DLG5 risk allele and the IBD5(risk) haplotype (IBD5(risk)) for MS. While there is no evidence of association within our MS sample with either of these polymorphisms, screening of 1027 subjects with SLE suggests that IBD5(risk) may have a modest contribution to disease risk in the subset of SLE subjects without lupus nephritis. In addition, a pooled analysis of existing published and unpublished data in 1305 cases of SLE genotyped for the CARD15 risk alleles suggests that only the CARD15(908R) IBD risk allele may have a strong effect on risk of SLE. Our data, therefore, suggest that both the CARD15 gene and the IBD5 locus may have a role as general susceptibility loci for certain common, genetically complex inflammatory diseases.

New genes in inflammatory bowel disease: lessons for complex diseases?

The chronic inflammatory bowel diseases Crohn's disease and ulcerative colitis are common causes of gastrointestinal disease in northern Europe, affecting as many as one in 250 people. Although mortality is low, morbidity associated with these diseases is substantial. We review the recent advances in the genetics of inflammatory bowel disease, with particular emphasis on the data that have been generated since the discovery of the CARD15 (NOD2) gene in 2001.

Recent advances in the etiology and treatment of inflammatory bowel disease

Crohn's disease and ulcerative colitis, together comprising the inflammatory bowel diseases, currently affect up to 2 million people in the western developed countries. The pathogenesis of the disease is a complex one in which genetic, immunogenic, microbial and environmental factors contribute to the etiology of the disease. Recent advances in understanding the molecular mechanisms that determine this complex entity have provided insight for promising new therapies.

Current status of genetics research in inflammatory bowel disease

The research on genetic susceptibility of inflammatory bowel diseases (IBD) has been tremendous and over 10 chromosomal regions have been identified by genome-wide scanning. Further fine mapping as well as candidate gene studies have already led to the identification of a number of susceptibility genes including CARD15, DLG5, OCTN1 and 2, NOD1, HLA, and TLR4. The CARD15 gene is undoubtedly replicated most widely and most understood at present. CARD15 is involved in the recognition of bacterial peptidoglycan-derived muramyl dipeptide (MDP) and will stimulate secretion of antimicrobial peptides including alpha-defensins (also called cryptdins) to protect the host from invasion. Genetic research in IBD has advanced our understanding of the clinical heterogeneity of the disease and has started to tackle the complex interactions between genetic risk factors and environmental risk factors in IBD. Genes also interfere with the metabolization of drugs and may influence the clinical response and the drug-related toxicity. Interesting pharmacogenetic data with respect to steroids, azathioprine, and infliximab have been generated in IBD. Overall, it is anticipated that genetic markers in the future will be implemented in an integrated molecular diagnostic and prognostic approach of our patients.

Gastroduodenal Crohn's disease is associated with NOD2/CARD15 gene polymorphisms, particularly L1007P homozygosity

Limited data exist on the specific association between gastroduodenal Crohn's disease (GDCD) and NOD2/CARD15 gene polymorphisms. The aim of this study was to assess the association between NOD2 polymorphisms and GDCD, and to assess the specific association between each of the 3 major allelic variants G908R, L1007P, and R702W and the clinical features of Crohn's disease. We retrospectively reviewed the records of 202 patients with confirmed Crohn's disease and complete data was performed. Seventy-one patients (35%) had at least 1 allelic variant: 55 had 1 variant, 4 were homozygous for L1007fs, 2 homozygous for R702W, and 10 were compound heterozygous. Eighteen patients with confirmed GDCD were identified; 10 (56%) had wild type, 4 (22%) had 1 variant, and 4 (22%) had 2 allelic variants (2 were L1007P homozygous and 2 compound heterozygous). Compared to patients without gastroduodenal involvement, those with GDCD were more likely to have 2 allelic variants (22% vs. 6%; odds ratio [OR] 2.7; 95% confidence interval [CI] 1.6-7.3) and to be homozygous for L1007P (11% vs. 1%; OR 5.2; 95% CI 2.5-9.4). G908R heterozygosity was associated with ileal involvement (OR 1.4; 95% CI 1.1-2.9) and smoking habits (OR 2.4; 95% CI 1.2-3.8), whereas L1007P homozygosity was associated with GDCD (OR 5.8; 95% CI 2.6-10.8). L1007P variation was associated with younger age at diagnosis as well. There was no specific association between R702W homo- or heterozygosity and any of the characteristics examined. In conclusion, GDCD is associated with double dose of the NOD2/CARD15 gene variants, particularly L1007P homozygosity. There is evidence of specific variant-phenotype associations. G908R heterozygosity is associated with ileal involvement and smoking, whereas L1007P homozygosity is strongly associated with GDCD and younger age at diagnosis.

Association of organic cation transporter risk haplotype with perianal penetrating Crohn's disease but not with susceptibility to IBD

BACKGROUND & AIMS

Three years after the identification of NOD2/CARD15, 2 more genes for inflammatory bowel diseases (IBDs) were reported. The carnitine/organic cation transporter (OCTN) on 5q31 (IBD5) is associated with Crohn's disease (CD) and DLG5 (10q23), a member of membrane-associated guanylate kinase (MAGUK) family, with IBD. We studied mutation prevalence, assessed phenotypic expression, and performed conditional analysis to examine evidence for gene-gene interactions.

METHODS

A cohort of 2032 individuals was genotyped for disease-associated OCTN and DLG5 variants, including 981 patients with IBD (CD, n = 769; ulcerative colitis, n = 186; indeterminate colitis, n = 26) followed up at a tertiary IBD center. For 373 patients, DNA from both parents was available (cohort 1) for transmission disequilibrium testing analysis; case-control analysis was performed in 608 patients and 305 controls (cohort 2).

RESULTS

There was no distortion of transmission toward affected offspring for any of the variant alleles. Case-control analysis also failed to shown an association. A higher frequency of DLG5 113A was observed in CARD15-positive patients (12.2%) compared with CARD15-negative patients (8.7%; P = .033). The OCTN-TC risk haplotype was associated with penetrating disease (odds ratio, 1.474; 95% confidence interval, 1.028-2.114; P = .035). For DLG5, there were no associations with a particular phenotype.

CONCLUSIONS

DLG5 and OCTN do not play a role in the susceptibility to IBD, CD, or ulcerative colitis in the Flemish population but play a role in the phenotypic expression of the disease. OCTN variants were associated with perianal and penetrating CD. More studies in independent populations are urgently needed to assess the validity of DLG5 and OCTN in the pathogenesis of IBD.

Genotype-phenotype analysis in childhood-onset Crohn's disease: NOD2/CARD15 variants consistently predict phenotypic characteristics of severe disease

INTRODUCTION

The incidence of early-onset CD in Scotland is among the highest worldwide. Three single nucleotide polymorphisms (SNPs) R702W, G908R and Leu1007finsC in the NOD2/CARD15 gene predispose to adult CD. We investigated the contribution of these variants to disease susceptibility and phenotype in the Scottish early-onset IBD population.

PATIENTS AND METHODS

906 individuals including 247 Scottish IBD patients aged <16 years at diagnosis, 414 parents and 245 controls were genotyped. Transmission disequilibrium testing (TDT), case-control analysis and detailed genotype-phenotype analysis were performed.

RESULTS

The Leu1007finsC variant was associated with susceptibility to CD by case-control (4.2% versus. 1.4%, P = 0.01) and TDT analysis (P = 0.006). The Population Attributable Risk (PAR) for the 3 NOD2/CARD15 mutations was 7.9%. Carriage of NOD2/CARD15 variants was associated with, at diagnosis: decreased albumin (31.0% versus. 9.0%, P = 0.001) and raised CRP (25% versus. 9.5%, P = 0.04) and at follow up: need for surgery (39.5% versus. 12.8%, P = 0.0002) jejunal involvement (50% versus. 18.4%, P = 0.01) jejunal and ileal involvement (50% versus. 10.7%, P = 0.009), raised CRP (57.1% and 12.8%, P = 0.0009), lower weight/height centile (75.0% versus. 20.2%, P = 0.03, 50.0% versus. 16.0%, P = 0.001 respectively) and stricturing disease (45.5% versus. 19.4%, P < 0.05). Multifactorial analysis demonstrated carriage was associated with need for surgery (P = 0.004, OR 4.9 [1.5-14.7]).

CONCLUSIONS

These NOD2/CARD 15 variants in the Scottish early onset CD population have a definite, albeit relatively small contribution to CD susceptibility (PAR 7.9%) but a major impact on phenotype. In particular NOD2/CARD15 variants are strongly associated with several markers of disease severity in pediatric CD, notably need for surgery.

CARD15/NOD2 polymorphisms do not explain concordance of Crohn's disease in Swedish monozygotic twins

BACKGROUND

CARD15/NOD2 polymorphisms are associated with Crohn's disease. There is a high concordance for disease and disease phenotype in monozygotic twin pairs with Crohn's disease.

AIM

We studied CARD15/NOD2 polymorphisms in a Swedish, population-based cohort of monozygotic twins with Crohn's disease to assess whether these variants explain disease concordance.

SUBJECTS AND METHODS

Twenty-nine monozygotic twin pairs (concordant n=9, discordant n=20) with Crohn's disease and 192 healthy controls were investigated for the CARD15/NOD2 variants Arg702Trp, Gly908Arg and Leu1007fsinsC.

RESULTS

CARD15/NOD2 mutations were found in 5/38 (13%) twins with Crohn's disease, corresponding to a total allele frequency of 6.6%. Only 2/9 concordant twin pairs carried any of the variants and the remaining seven were wild type genotype. The total allele frequency was 4.4 times higher (95% confidence interval 1.0-21.5, p=0.06) in concordant twins than in discordant ones, 11.1% versus 2.5%. In healthy controls the total allele frequency was 2.6%.

CONCLUSIONS

CARD15/NOD2 polymorphisms contribute but do not alone explain concordance of Crohn's disease in monozygotic twins and, at least in a Swedish population, other polymorphisms are required. The low occurrence of CARD15/NOD2 mutations in the study and other Northern European populations suggests that these variants are of less importance in Northern Europe.

Consequence of functional Nod2 and Tlr4 mutations on gene transcription in Crohn's disease patients

The concept that mutations in germ-line encoded pattern recognition receptors with immune activating functions are associated with an increased incidence in Crohn's disease (CD) is gaining acceptance. Whether these mutations have similar or distinct effects on cellular physiology remains obscure. The incidence of three single nucleotide polymorphisms (SNPs) within the Nod2 gene and one functional SNP within both the Tlr4 and Tlr5 gene in a Dutch cohort of 637 patients with inflammatory bowel disease and 127 controls was investigated. The functional consequence of mutant NOD2 and TLR4 was investigated by comparing gene expression profiles after stimulation of monocyte-derived dendritic cells (DCs) from homozygous TLR4- and NOD2-mutant patients with lipopolysaccharides and peptidoglycan, respectively. We observed that the R702W and 1007fs Nod2 alleles and the A299G Tlr4 alleles were significantly more prevalent in patients with CD as compared to healthy controls or patients with ulcerative colitis. The phenotype of TLR4- and NOD2-mutant DCs is distinct, but a large number of genes are up- or down-regulated concordantly. These data provide a concept for the genetic basis of CD; mutations in innate immunity cause similar effects on gene transcription and finally result in comparable clinical disease presentation.

Variants of CARD15 are associated with an aggressive clinical course of Crohn's disease--an IG-IBD study

BACKGROUND

Three major variants of the CARD15 gene confer susceptibility to Crohn's disease (CD). Whether or not these variants correlate with specific clinical features of the disease is under evaluation.

AIM

We investigated the possible association of CARD15 variants with specific clinical characteristics, including the occurrence of anti-Saccharomyces cerevisiae antibodies (ASCA) and antineutrophil cytoplasmic antibodies (ANCA), in a large cohort of inflammatory bowel disease (IBD) patients and their unaffected relatives.

METHODS

Three hundred and sixteen CD patients (156 with positive family history), 408 ulcerative colitis (UC) patients (206 with positive family history), 588 unaffected relatives, and 205 unrelated healthy controls (HC) were studied. Single nucleotide polymorphisms (SNPs) R702W, G908R, and L1007finsC of the CARD15 gene were investigated and correlated to age at diagnosis, gender, family history, localization, extraintestinal manifestations, previous resective surgery, stenosing/fistulizing pattern, ANCA, and ASCA.

RESULTS

Compared to HC, the frequencies of all three variants in CD were significantly increased: 8.7% versus 4.1% for R702W (p < 0.006), 7.3% versus 2.7% for G908R (p < 0.002), 9.3% versus 0.7% for L1007finsC (p < 0.00001). At least one risk allele was found in 38.2% (p < 0.0001, compared to HC), 13.7% (NS), and 15.1% of CD, UC, and HC, respectively. The L1007finsC risk allele was also significantly increased in unaffected relatives of familial (9.5%; p < 0.00001), and sporadic CD (9%; p < 0.00001), compared to HC (0.7%). Sixteen healthy relatives, carriers of two risk alleles, were asymptomatic after 5-8 yr of follow-up. CD carriers of at least one variant were younger (p= 0.03), more likely to have ileal localization (p= 0.0001), stenosing pattern (p= 0.01), previous resective surgery (p= 0.0001), and presence of ASCA (p= 0.0001). No difference in SNPs frequency between familial and sporadic cases of CD was found.

CONCLUSION

In our population, both familial and sporadic CD patients carrying at least one major variant of CARD15 had an aggressive clinical course.

Genetic Testing in Crohn Disease

Inflammatory bowel disease (IBD), with its two subforms of Crohn disease and ulcerative colitis, is a polygenic disease that manifests due to environmental trigger factors on the background of a complex genetic predisposition. The first risk gene underlying susceptibility to Crohn disease has been identified as CARD15 (located on chromosome 16q12, encoding NOD2). Three single nucleotide polymorphisms in the leucine rich region (LRR) of this gene are strongly and independently associated with Crohn disease susceptibility and explain up to 20% of the total genetic predisposition for Crohn disease. These variants have been consistently replicated as associated with a particular sub-phenotype characterized by small bowel (ileum) involvement and early age at onset. Presently, genetic testing for the CARD15 variants has only a modest relevance in clinical practice. The most attractive use of genetic testing is for the prediction of response to therapy. Most therapies only show efficacy in subgroups of patients and no clinical parameters are available to distinguish, prior to therapy, whether the patients will be responders or non-responders, or if the patients will experience adverse effects. The pharmacogenetic basis of toxicity is well known for azathioprine: several thiopurine methyltransferase (TPMT) polymorphisms that are associated with reduced activity of this thiopurine drug metabolizing enzyme result in cytotoxic and immunosuppressive adverse effects of azathioprine. Genetic screening, which has found its way into routine clinical diagnostics, allows the identification of the patients who will not tolerate a standard dose of the drug. The extensive search for genetic predictors of response to the anti-tumor necrosis factor treatment with infliximab, which results in a remission rate of 30-40%, has, however, failed to identify a variation associated with a differential response.

Sero-reactivity to microbial components in Crohn's disease is associated with disease severity and progression, but not NOD2/CARD15 genotype

BACKGROUND AND AIMS

Antibodies directed against the porin protein C of Escherichia coli (anti-OmpC) and Pseudomonas fluorescens (anti-I2) have recently been described in Crohn's disease (CD). Those directed against Saccharomyces cerevisiae (ASCA) and the perinuclear component of neutrophils (pANCA) have been more widely studied and may be of diagnostic importance. We aimed to assess the frequency of anti-OmpC, anti-I2, ASCA, and pANCA, in an independent Scottish CD cohort, establish phenotypic associations, and compare with a U.S. cohort.

METHODS

One hundred and forty-two well-characterized CD patients (76 females, median age 39 yr (17-88)) were studied. CD was classified by the Vienna classification. Sera were assayed for anti-OmpC, anti-I2, ASCA, and pANCA. Allele specific primers were used for NOD2/CARD15 genotyping.

RESULTS

Anti-OmpC, anti-I2, ASCA, and pANCA were present in sera from 37%, 52%, 39%, and 14% of CD patients, respectively. Multivariate analysis demonstrated independent associations of anti-OmpC to be progression of disease type (p= 0.005) and long disease duration (p= 0.002), and those of anti-I2 to be long disease duration (p= 0.002) and the need for surgery (p= 0.033). ASCA were associated with disease progression (p < 0.001). When the presence and magnitude of all antibody responses were considered, reactivity to microbial components was associated with long disease duration (p < 0.001), progression of disease type (p < 0.001), penetrating disease (p= 0.008), small bowel disease (p < 0.02), and the need for surgery (p < 0.001). There was no association of antibody status to NOD2/CARD15 genotype.

CONCLUSION

Reactivity to microbial components is associated with severe CD characterized by small bowel involvement, frequent disease progression, longer disease duration, and greater need for intestinal surgery.

Analysis of the CARD15 variants R702W, G908R and L1007fs in Italian IBD patients

CARD15 on chromosome 16 is the only IBD susceptibility gene identified among several mapped loci. Its recurrent variants R702W, G908R and L1007fs have shown significant association with Crohn's disease (CD), but not with ulcerative colitis (UC), in different Caucasian populations. We analysed these three variants in 184 CD and 92 UC Italian patients and in 177 healthy controls. L1007fs and G908R were independently associated with CD, while R702W showed a nonsignificant increase. After combining the three variants together, 32.6% of CD patients were positive vs 18.6% of the controls. The association was stronger for homozygotes and compound heterozygotes, OR 13.9 (1.8-108), and weaker but still significant for simple heterozygotes, OR 1.7 (1.0-2.9). An excess of homozygotes/compound heterozygotes also resulted from the comparison with Hardy-Weinberg expectations. Phenotype-genotype correlations were analysed first by univariate logistic regression and then by multivariate analysis, the effect of CARD15 positivity being adjusted according to the status of smoking, familiarity and sex, so as to focus on the predictivity of genetic and environmental risk factors on the clinical phenotype. Significant risk estimates of the CARD15 genotype were obtained for stricturing vs inflammatory behaviour, OR 2.76 (1.2-6.3), and for penetrating behaviour, 2.59 (1.0-6.6), and marginally significant for ileal vs colic location, OR 3.0 (0.9-9.8). Our findings indicate that the association of the CARD15 genotype with behaviour and location of disease holds also for the Italian population.

Association of NOD2/CARD15 variants with Crohn's disease in a Greek population

OBJECTIVE

Single nucleotide polymorphisms in the NOD2/CARD15 gene have recently been shown to be associated with Crohn's disease (CD), but whether this susceptibility extends to all ethnic groups and geographic areas remains unknown. The aim of the present study was to evaluate the NOD2/CARD15 mutations in Greek patients with CD.

METHODS

Individuals were genotyped for three NOD2/CARD15 mutations: R702W, G908R and L1007fsinsC. Blood samples were obtained from 120 patients with CD, 85 patients with ulcerative colitis, and 100 unrelated healthy controls.

RESULTS

Mutations in NOD2/CARD15 were observed with significantly greater frequency in CD patients (98/120, 81.7%) than in ulcerative colitis patients (40/85, 47%) (P < 0.0001) or in healthy individuals (21/100, 21%) (P < 0.0001). For CD patients, compared with controls, the odds were increased for carriage of the R702W (odds ratio, 12.25) and less for the G908R (odds ratio, 5.2) and L1007fsinsC (odds ratio, 3.9) mutations. The age of onset of CD was lower in Greek mutation carriers as compared with non-carriers of Greek origin (28.2 +/- 14.6 years versus 34 +/- 12.3 years, respectively; P = 0.036). Additionally, the frequency of NOD2/CARD15 mutations was increased in ileitis or ileocolitis compared with non-ileal disease.

CONCLUSIONS

The NOD2/CARD15 mutations are risk factors for CD in Greece, they appear to predict an earlier age of onset and are associated particularly with ileitis or ileocolitis.

NOD2/CARD15 mutations and presence of granulomas in pediatric and adult Crohn's disease

OBJECTIVES

The etiology and mechanism leading to granuloma formation in patients with Crohn's disease (CD) are presently unknown. The first susceptibility gene to be identified as a risk factor for CD is the NOD2/CARD15 gene on Chromosome 16. Mutations in NOD2 could affect the intracellular response to bacterial products and may eventually lead to granuloma formation. The association between NOD2 and granulomas has not been previously explored. We evaluated a possible association between NOD2 mutations and granuloma formation, and compared the prevalence of granulomas in both pediatric and adult cohorts.

METHODS

Patients were consecutively recruited through pediatric gastroenterology and adult gastroenterology programs. Patients were eligible if CD was confirmed, and they had undergone full colonoscopy with biopsy and/or surgical resection. Patients underwent genotyping for NOD2 disease-associated mutations.

RESULTS

A total of 230 patients were enrolled into the study, of whom 169 patients met all inclusion/exclusion criteria (Group 1, 77 patients [age range 1-16 years]; Group 2, 92 patients [age range 17-68 years]). Surgical resection was performed more often in adults (P < 0.005), and gastroscopy was performed more frequently in children (P < 0.001). Granulomas were found in 34% of the patients studied. The prevalence of granulomas did not differ by age, age group, or gender. A disease-associated NOD2 mutation was found in 37.8% of patients. Granulomas were found in 39% of patients with NOD2 mutations compared with 31% of those without NOD 2 mutations (difference was not significant). In addition, no difference was noted for the specific mutations.

CONCLUSIONS

We did not find any correlation between NOD2 mutations and granuloma formation. The cause of granulomas in CD remains elusive.

Disease location, anti-Saccharomyces cerevisiae antibody, and NOD2/CARD15 genotype influence the progression of disease behavior in Crohn's disease

BACKGROUND

Crohn's disease (CD) is characterized by heterogeneity of phenotype. The Vienna classification can be used to classify CD, and recent data illustrate that behavior evolves over the course of the disease. Clinical and biological influences on disease progression remain unclear. We examined the associations of CD disease progression at diagnosis and for up to 20 years of follow-up.

METHODS

Two hundred thirty-one well-characterized CD patients were studied. Demographic, clinical, and NOD2/CARD15 data were collected. Disease behavior according to the Vienna classification was assessed at diagnosis and for up to 20 years following diagnosis.

RESULTS

At diagnosis, 70% of patients had inflammatory disease, 9% stricturing, and 21% penetrating. Early age at diagnosis was associated with ileocolonic and upper GI disease (p = 0.015), and positive anti-Saccharomyces cerevisiae antibody (ASCA) was associated with ileal involvement (p = 0.008). Smoking was relatively protective against colonic, rather than ileal involvement at diagnosis (p < 0.02). At 20 years, 92% had progressed to a more severe disease type. Patients who progress to a more severe disease type require more frequent surgery (p < 0.00001). Multivariate analysis found disease progression to be associated with ileal disease location (p = 0.001) and positive ASCA (p = 0.003). Variant NOD2/CARD15 alleles were protective against rapid progression of disease phenotype (p = 0.04). The presence of perianal disease was independent of intestinal penetrating disease.

CONCLUSIONS

The progression of disease type in CD is associated with the need for more frequent surgery. Rapid progression is associated with ileal disease and positive ASCA, and delayed progression is associated with variant NOD2/CARD15 alleles. Consideration should be given to a separate Vienna classification for perianal disease.

Update in inflammatory bowel disease pathogenesis

PURPOSE OF REVIEW

During the last few years, significant advances have been achieved in the understanding of the pathogenesis of inflammatory bowel disease (IBD). By gaining new insights, paradigms that seemed to be a safe basis of our knowledge on IBD pathogenesis have recently become doubtful. This review discusses and summarizes the most recent developments.

RECENT FINDINGS

Important new insights have been gained into the function of caspase-activating and recruitment domain-15 (CARD15)/NOD2, the first cloned susceptibility gene for Crohn disease (CD). New data on CARD15/NOD2 function and nuclear factor-kappaB activation indicate that an inflammatory reaction of the intestinal mucosa as a response of the innate immune system may be necessary for the maintenance of gut homeostasis. CD may therefore be seen as a defective immune response, no longer only as hyperresponsiveness of the mucosal immune system. Data on CARD15/NOD2 expression suggest that macrophages and epithelial cells could be the site of a primary pathophysiologic defect, and T-cell activation might just be a secondary effect inducing chronification of the inflammation, perhaps as a backup mechanism to a defective innate immunity. In addition to CARD15/NOD2, there are additional "innate" pathways by which commensal and pathogenic bacteria can directly interact with cells of the intestinal mucosa (eg, toll-like receptors). The "germ concept" and the "genetic concept" of IBD pathophysiology are converging.

SUMMARY

New findings are changing our concepts of the pathogenesis of IBD. The innate immune system, early responses to bacterial products, and the modulation of T-cell responses are important aspects that are reviewed.

Unravelling the complex genetics of inflammatory bowel disease

The rapid pace of progress in molecular genetics over the past 15 years--since the seminal description of the polymerase chain reaction--has led to the identification of the genes involved in many single gene disorders. These successes in the laboratory have already led directly to clinical applications in diagnosis, pharmacogenetics, and the development of new therapies. Progress in unravelling the genetics of complex diseases has been less straightforward. However, real excitement has followed the identification of the NOD 2/CARD 15 gene as an important determinant of susceptibility to Crohn's disease.(1,)(2) Not only has this finding provided a proof of principle for the technique of genome-wide scanning in complex disorders, but the discovery also has given real insight into the primary pathophysiology involved in chronic inflammatory bowel disease. The background to this discovery and its implications form the basis for the present article.