Frequency of NOD2/CARD15 variants in both sporadic and familial cases of Crohn's disease across Italy. An Italian Group for Inflammatory Bowel Disease Study

CARD15 Gene 3020insC Mutation with Inflammatory Bowel Diseases Patients in the Black Sea Region of Turkey

BACKGROUND: The role of the CARD15 gene 3020insC frameshift mutation in the pathogenesis of inflammatory bowel diseases (IBD) investigated without a definitive conclusion. The incidence of this mutation in Turkish patients with Crohn’s disease is not known.OBJECTIVE: We investigated whether the CARD15/NOD2 3020insC frameshift mutation is a risk factor for patients with inflammatory bowel disease in Black Sea Region population in Turkey.METHODS: We studied 3020insC mutation of CARD15/NOD2 gene by allele-specific multiplex PCR in 69 patients with IBD (18 Crohn’s disease [CD] and 51 ulcerative colitis [UC]) and 101 ethnically matched healthy controls.RESULTS: CARD15/NOD2 3020insC frameshift mutation was positive in 7/18 (38.8 %), 13/51 (25.5 %), and 4/101 (4 %) of CD, UC, and healthy control groups, respectively. None of the controls or patients with Crohn’s disease and ulcerative colitis was homozygous for this mutations.CONCLUSION: This study is to investigate a relation between CARD15/NOD2 3020insC frameshift mutation and in patients with IBD in the Turkish Population. C-insertion frameshift mutation is a major contributor to the susceptibility to both CD and UC, but it is not specific to patients with CD in Turkish population.

Association of the MEFV gene variations with inflammatory bowel disease in Turkey

BACKGROUND

Association of NOD2 (CARD15) gene mutations with inflammatory bowel diseases (IBD) is well known. We herein aimed to investigate the role of familial Mediterranean fever-associated MEFV variations in IBD patients as additional regional-specific risk factor.

STUDY

One hundred thirty-seven (78 female, 56.9%) IBD patients [62 Crohn's disease (CD), 75 ulcerative colitis (UC)] were enrolled into the study. The diagnosis of all patients was confirmed by colonoscopy, histopathology, and the clinical findings. One hundred one healthy donors' samples were used as healthy controls. All patients were genotyped for the most common E148Q, M608I, M694V, and V726A variations of the MEFV and R702W, G908R, and 1007fs of the NOD2.

RESULTS

The overall MEFV variation frequency was found to be higher in the IBD (25.5%) patients (28% in UC, 22.6% in CD) compared with controls (9.9%, P=0.006). This association was stronger with the penetrant exon 10 variations (M694V, M680I, V726A; odds ratio =4.5, P=0.001). Contribution of M694V was higher compared with the other variations (14.5% in CD, 17.3% in UC and 3% in controls, odds ratio =6.039, 95% confidence intervals, 1.7-20.7, P=0.002). The overall frequency of 3 NOD2 variants in the IBD group was not different from that of controls.

CONCLUSIONS

The results of this study suggest that the MEFV variations may be an additional susceptibility factor for IBD in certain parts of the world where the carrier rate is high, and the genetic background of the IBD patients may show regional changes.

CARD15 gene variants and risk of reoperation in Crohn's disease patients

OBJECTIVES

Several studies have investigated, with conflicting results, the risk factors for reoperation in Crohn's disease (CD) patients. CARD15 gene variants have been identified as a major genetic risk factor for CD patients and associated with ileal disease, stenosis, and risk of surgery. However, data regarding the association between these variants and the need for reoperation are very few and conflicting. This study evaluated the risk factors of reoperation, including CARD15 gene variants.

METHODS

A total of 253 consecutive CD patients, recruited in four Italian tertiary-care inflammatory bowel disease (IBD) referral centers, who had submitted to surgery for CD, were included in the study. Clinical characteristics of CD patients, time and main indications for surgery, type of operation, postoperative therapy, and time to second surgery were recorded. CARD15 gene variants were determined by DNA sequencing analysis in each center. Factors related to surgical recurrence, including CARD15 variants, were estimated by Cox proportional hazard regression.

RESULTS

In all, 89 patients (35.1%) showed at least one surgical recurrence. Reoperation was significantly correlated with stenosis as indications at initial surgery only. CARD15 variants were found in 36.0% of patients, but did not correlate significantly with the demographic and clinical characteristics of the patients, rate of first surgical recurrence, and time to second operation. CARD15 variants did not significantly affect the reoperation rate, irrespective of indications for surgery.

CONCLUSIONS

Reoperation for CD is correlated with stenosis at initial surgery, but not with CARD15 gene variants. This finding does not justify more aggressive prophylactic therapy on the basis of CARD15 genotype.

Identification of NOD2/CARD15 mutations in Malaysian patients with Crohn's disease

OBJECTIVE

The NOD2/CARD15 gene has been identified as an important susceptibility gene for Crohn's disease (CD) but the three common disease predisposing mutations (DPM) found in developed countries have not been identified in Asian populations. The aim of our study was to look for the DPM in our multiracial population and to discover whether there were any differences in the three major ethnic groups; Malay, Chinese and Indian.

METHODS

Blood samples from consecutive CD patients and healthy controls were obtained and analyzed for the three common mutations (R702W, G908R, 1007fs) but in addition to this, we also looked for the SNP5 and JW1 variants which are associated with CD in Ashkenazi Jews. A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique was used to identify the mutations, which was confirmed by sequencing. The baseline socio-demography and clinical characteristics of the CD patients were recorded.

RESULTS

Overall 45 patients (three Malays, 15 Chinese, 26 Indians and one other) with confirmed CD and 300 controls were recruited. The three common DPM were not observed in either the CD patients or the controls. Neither the SNP5 nor the JW1 mutation was found in any of the controls. However, the SNP5 mutation was identified in six (13.3%) Indian CD patients and the JW1 mutation in eight CD patients who are different from those carrying the SNP5 mutation: one Malay (33.3%), two Chinese (13.3%), one other (Portuguese) and four Indians (15.4%). The presence of SNP5 was strongly associated with CD in the Indian population and that of JW1 was strongly associated with CD overall and in each of the major ethnic groups. There was a trend towards a younger age of onset and stricturing disease in patients carrying the JW1 mutation.

CONCLUSION

These findings suggest the presence of novel DPM in the NOD2/CARD15 gene in Asian patients with 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.

Clinical significance of NOD2/CARD15 and Toll-like receptor 4 gene single nucleotide polymorphisms in inflammatory bowel disease

AIM: To evaluate the role of genetic factors in the pathogenesis of Crohn’s disease (CD) and ulcerative colitis (UC), we investigated the single nucleotide polymorphisms (SNPs) of NOD2/CARD15 (R702W, G908R and L1007finsC), and Toll-like receptor 4 (TLR4) genes (D299G and T399I) in a selected inflammatory bowel disease (IBD) population coming from Southern Italy.

METHODS: Allele and genotype frequencies of NOD2/CARD15 (R702W, G908R and L1007finsC) and TLR4 (D299G and T399I) SNPs were examined in 133 CD patients, in 45 UC patients, and in 103 healthy controls. A genotype-phenotype correlation was performed.

RESULTS: NOD2/CARD15 R702W mutation was significantly more frequent in CD (9.8%) than in controls (2.4%, P = 0.001) and in UC (2.3%, P = 0.03). No significant difference was found between UC patients and control group (P > 0.05). In CD and UC patients, no significant association with G908R variant was found. L1007finsC SNP showed an association with CD (9.8%) compared with controls (2.9%, P = 0.002) and UC patients (2.3%, P = 0.01). Moreover, in CD patients, G908R and L1007finsC mutations were significantly associated with different phenotypes compared to CD wild-type patients. No association of IBD with the TLR4 SNPs was found in either cohort (allele frequencies: D299G-controls 3.9%, CD 3.7%, UC 3.4%, P > 0.05; T399I-controls 2.9%, CD 3.0%, UC 3.4%, P > 0.05).

CONCLUSION: These findings confirm that, in our IBD patients selected from Southern Italy, the NOD2/CARD15, but not TLR4 SNPs, are associated with increased risk of CD.

Variants of CARD15, TNFA and PTPN22 and susceptibility to Crohn's disease in the Czech population: high frequency of the CARD15 1007fs

Crohn's disease (CD) has been shown to be associated with the variants in the CARD15 gene as well as in other genes involved in the immune response. The frequencies of the variants profoundly differ among populations and so does the associated risk. We examined the associations of variants in the CARD15, TNFA and PTPN22 genes with pediatric-onset and adult-onset CD in the Czech population. Genotype, phenotype and allelic frequencies were compared between 345 patients with CD (136 pediatric-onset and 209 adult-onset patients) and 501 unrelated healthy controls. At least one minor allele of the CARD15 gene was carried by 46% patients and only 21% control subjects (OR = 3.2, 95% CI 2.4-4.4). In a multiple logistic regression model, the strongest association with CD was found for the 1007fs variant (OR = 4.6, 95% CI 3.0-7.0), followed by p.G908R (OR = 2.9, 95% CI 1.5-5.7) and p.R702W (OR = 1.7, 95% CI 1.0-2.9), while no independent association was found for the remaining variants in the CARD15 gene (p.268S, p.955I and p.289S), for the p.R620W variant in the PTPN22 gene or for the g.-308G>A variant in the TNFA gene. The age at CD onset was strongly modified by positivity for the 1007fs allele: it was present in 42% pediatric-onset and only 25% adult-onset patients. In conclusion, we report a high frequency of the minor allele of the CARD15 1007fs polymorphism in the Czech population and a strong effect of this allele on the age at disease onset.

Epidemiology, genes and inflammatory bowel diseases in childhood

There is evidence that inflammatory bowel disease is immunologically mediated and that genetic factors play an important aetiological role. The identification of disease susceptibility genes has led to significant progress in our understanding of the pathogenesis of Crohn's disease. Genes linked to Crohn's disease play critical roles in the normal function of the innate immune system, and genes linked to epithelial integrity may play a role in the pathogenesis of inflammatory bowel disease as well. However, the dynamic epidemiology of both Crohn's disease and ulcerative colitis suggests that extrinsic environmental factors acting at the population level may be involved in their pathogenesis. These environmental factors may be responsible for the rising incidence of inflammatory bowel disease.

Pediatric onset Crohn's colitis is characterized by genotype-dependent age-related susceptibility

BACKGROUND

Pediatric onset Crohn's disease (CD) is associated with more colitis and less ileitis compared with adult onset CD. Differences in disease site by age may suggest a different genotype, or different host responses such as decreased ileal susceptibility or increased susceptibility of the colon.

METHODS

We evaluated 721 pediatric onset CD patients from 3 cohorts with a high allele frequency of NOD2/CARD15 mutations. Children with isolated upper intestinal disease were excluded. The remaining 678 patients were evaluated for interactions between age of onset, NOD2/CARD15, and disease location.

RESULTS

We found an age-related tendency for isolated colitis. Among pediatric onset patients without NOD2/CARD15 mutations, colitis without ileal involvement was significantly more common in first-decade onset patients (P = 4.57 x 10(-5), odds ratio [OR] 2.76, 95% confidence interval [CI] 1.72-4.43). This was not true for colonic disease with ileal involvement (P = 0.35), or for isolated colitis in patients with NOD2/CARD15 mutations (P = 0.61). Analysis of 229 patients with ileal or ileocolonic disease and a NOD2/CARD15 mutation disclosed that ileocolitis was more prevalent through age 10, while isolated ileitis was more prevalent above age 10 (P = 0.016). NOD2/CARD15 mutations were not associated with age of onset.

CONCLUSIONS

In early-onset pediatric CD, children with NOD2/CARD15 mutations demonstrate more ileocolitis and less isolated ileitis. Young children without NOD2/CARD15 mutations have an isolated colonic disease distribution, suggesting that this phenotype is associated with genes that lead to a specific phenotype of early-onset disease.

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.

Multidrug resistance 1 gene polymorphism and susceptibility to inflammatory bowel disease

BACKGROUND

Several studies have evaluated the role of the multidrug resistance 1 gene (MDR1) polymorphism, which encodes the membrane-bound efflux transporter P-glycoprotein 170, in determining susceptibility to and disease behavior in inflammatory bowel disease (IBD), but with conflicting results.

METHODS

A total of 211 patients with Crohn's disease (CD), 97 patients with ulcerative colitis (UC), and 212 control subjects were investigated for the presence of MDR1 G2677T/A and C3435T polymorphisms. Genotype frequencies of CD and UC patients were compared to those observed in a control population. Genotype-phenotype correlations with major clinical features were also established and estimated risks (odds ratio [OR] with 95% confidence interval [CI]) for the mutations were calculated by a logistic regression analysis and multiple correspondent analysis.

RESULTS

No significant difference was observed for genotype frequencies for both MDR1 G2677T/A and C3435T polymorphisms on overall disease susceptibility for either CD or UC patients compared with control subjects. A significant association was found between the MDR1 C3435T polymorphism and patients with ileo-colonic CD (OR = 3.34; 95% CI: 1.34-8.27). Interestingly, a negative association was found between MDR1 C3435T polymorphism in patients with a positive family history for IBD (OR = 0.44; 95% CI: 0.20-0.95) and articular manifestations (OR = 0.29; 95% CI: 0.13-0.68). Both susceptible and protective effects were identified. No significant association between G2677T/A polymorphism and any specific subphenotypes was found, nor was there any association with subphenotypic categories of UC and both single nucleotide polymorphisms.

CONCLUSIONS

The results of our study suggest that MDR1 gene polymorphism could have a role in determining susceptibility to IBD. The variability of this possible effect in the several studies reported so far may be the indirect expression of the complex role played by the MDR1 gene and its product, P-glycoprotein 170, in the regulation of host-bacteria interactions and in the pathogenesis of IBD.

A population-based case-control study of CARD15 and other risk factors in Crohn's disease and ulcerative colitis

OBJECTIVES

Multiple established Crohn's disease (CD) and ulcerative colitis (UC) risk factors including family history, tobacco use, Jewish ethnicity, urban residency, and CARD15/NOD2 mutations have been evaluated singly and in hospital-based observational studies. The goal of this study was to assess the relative contributions of all these risk factors jointly in a nonreferral, population-based cohort derived from a population epidemiologic database.

METHODS

CD (N = 232) and UC (N = 121) subjects were ascertained from our population-based IBD Registry derived from Manitoba Health, the single provincial insurer. Healthy controls (HC) (N = 336) were recruited via a 10:1 mailing matched for age, sex, and postal code. Ethnicity, tobacco use, family history, residency, and CARD15/NOD2 genotype status were determined.

RESULTS

In both univariate analyses and analyses adjusted for all risk factors, CD was influenced independently by CARD15/NOD2 heterozygote and homozygote/compound-heterozygote status (adjusted odds ratios [OR] 3.7 and 40.0, respectively), Jewish ethnicity (OR 18.5), CD family history (OR 6.2), and smoking (OR 3.0 current and 1.7 ex-smoker, respectively). Penetrance for homozygote/compound-heterozygotes was 4.9%, heterozygotes 0.54%, and wild types 0.184%. Population attributable risk for CARD15 was 26.7% and current tobacco use was 46.8%. A tobacco-CARD15 interaction was not observed. UC was influenced by Jewish ethnicity (OR 37.1), and by family history (OR 2.6), ex-smoker status (OR 1.9), and CARD15/NOD2 heterozygote or homozygote/compound-heterozygote status (OR 1.9 and 6.4, respectively) in adjusted analyses only.

CONCLUSIONS

CARD15/NOD2, family history, smoking, and Jewish ethnicity are independent risk factors for CD. Examination of these risk factors together in a single population-based cohort has provided initial data for population epidemiological characterization and genetic counseling uses.

Incidence of Crohn’s disease and CARD15 mutation in a small township in Sicily

BACKGROUND

The incidence of Crohn's disease (CD) has been shown to be lower in Southern than in Northern Europe. Data on the frequency of the NOD2/CARD15 mutations for Mediterranean area are very scant.

AIM

To determine the incidence of CD from 1979 to 2002 in a township in Sicily together with the allele frequency of NOD2/CARD15 mutations in patients, family members and controls, and to determine the allele frequency of these mutations in sporadic CD from other areas of Sicily in comparison with a control population.

METHODS

Casteltermini is a small town close to Agrigento (Sicily) with a population of 9,130 inhabitants. All the diagnoses of inflammatory bowel disease (IBD) made from 1979 to 2002 were obtained through the local health authority. NOD2/CARD15 mutations were studied in 23 out of the 29 patients with CD in Casteltermini, in 60 family members and in 64 controls. NOD2/CARD15 was also studied in 80 sporadic cases of CD disease among Sicilians outside Casteltermini and 118 healthy controls.

RESULTS

From 1979 to 2002, 29 patients with CD and 13 patients with ulcerative colitis (UC) were registered. The 6-year mean incidence of CD ranged from 8.0 to 17 new cases for every 100,000 inhabitants, whereas the mean incidence of UC ranged from five new cases to 7.8 for every 100,000 inhabitants. The allele frequencies of NOD2/CARD15 mutations (L1007finsC, G908R, R702W) were 8.7, 4.3 and 8.7%, respectively, in CD cases; 5.0, 4.2 and 3.1% in family members; 1.6, 2.3 and 3.1% in controls. In sporadic Sicilian CD patients outside Casteltermini the allele frequency was 7.5, 8.1, 6.2% whereas in control population it was 3.3, 1.6, 1.6%.

CONCLUSIONS

A high incidence of CD compared with UC was observed in this small town in Southern Italy. The frequency of NOD2/CARD15 mutations in CD is similar to other Caucasian population studied so far.

Homozygosity for the CARD15 frameshift mutation 1007fs is predictive of early onset of Crohn's disease with ileal stenosis, entero-enteral fistulas, and frequent need for surgical intervention with high risk of re-stenosis

OBJECTIVE

The identification of CARD15 as a susceptibility gene for Crohn's disease (CD) offers new possibilities for patient classification and risk assessment. The purpose of this study was to carry out a CARD15 sequence analysis in a large single-center IBD cohort and to investigate the impact of different genotypes on disease phenotypes.

MATERIAL AND METHODS

A total of 445 unrelated patients with IBD (68.1% CD, 28.5% ulcerative colitis (UC), 3.4% indeterminate colitis (IC)) were included in the study. Clinical data were recorded by detailed questionnaire and analysis of the charts. CARD15 variants (R702W, G908R, 1007fs (frameshift)) were identified by DNA sequence analysis.

RESULTS

CARD15 variants were found in 142 inflammatory bowel disease (IBD) patients (31.9%) including 120 CD patients (39.6%). In CD, the presence of two CARD15 variants was associated with ileal disease (p=0.008 versus wild-type (wt); OR 4.04; 95% CI 1.36-11.96) and a fibrostenotic phenotype (p=0.002 versus wt; OR 5.47; 95% CI 1.61-18.58). Subgroup analysis of 19 patients (4.3%) homozygous for the CARD15 variant 1007fs (3020ins C) revealed an association with onset of CD at an early age (p=0.014 versus wt), ileal involvement (p=0.001), and intestinal stenoses in all patients (p=0.001) frequently requiring surgery (73.7%; p=0.093). Of these patients 78.6% developed re-stenoses after surgical resection; 52.6% of the homozygotes were diagnosed as having entero-enteral fistulas.

CONCLUSIONS

Patients homozygous for the 1007fs mutation had an early disease onset with long-segment ileal stenoses and entero-enteral fistulas. They frequently needed surgical intervention and had a high risk of re-stenosis. Genotyping therefore appears to be an important diagnostic tool in identifying severely affected patients requiring individualized treatment strategies at an early stage of the disease.

Associations between NOD2/CARD15 genotype and phenotype in Crohn’s disease-Are we there yet?

There have been multiple NOD2/CARD15 genotype-phenotype analyses undertaken in patients with Crohn's disease since the gene’s discovery in 2001. This review focuses on the major published series based upon their size and on the presence of specific clinical and genetic information provided in the published material from 2001 to 2005. Twelve studies provided raw data to carry out comparisons of disease location while ten studies included analysis of NOD2/CARD15 genotypes. NOD2/CARD15 variant frequency in ileal disease did not differ significantly among studies, whereas a comparison of disease location demonstrated highly significant differences among studies. Meta-analysis confirmed significant associations between NOD2/CARD15 variants and both ileal and ileocolonic disease locations, and with both stricturing and penetrating forms of disease behavior. This review underlines the significant phenotypic differences that exist among populations, including similar ethnic groups, and has demonstrated the need for further studies of patients with long-term “inflammatory” Crohn’s disease.

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.

Family and twin studies in inflammatory bowel disease

Studies examining the inheritance of inflammatory bowel disease (IBD) within different family groups have been the basis for recent molecular advances in the genetics of IBD. The derived heritability in Crohn’s disease (CD) is higher than in many other complex diseases. The risk of IBD is highest in first-degree relatives of a CD proband, but first-degree relatives of a proband suffering from ulcerative colitis (UC) and more distant relatives are also at increased risk. Disease concordance rates in IBD have been examined in multiplex families and in three large European twin studies.

Increased intestinal permeability and NOD2 variants in familial and sporadic Crohn's disease

BACKGROUND

Abnormal barrier function may be genetically determined in Crohn's disease.

AIM

To examine the role of abnormal intestinal permeability in genetic predisposition in multiplex vs. sporadic Crohn's disease families.

METHODS

Intestinal permeability was measured in patients, relatives and partners by means of lactulose/mannitol test. Healthy subjects from the hospital staff served as controls. CARD15 mutations were investigated in sporadic and familial Crohn's disease patients and in a group of blood donors.

RESULTS

The median lactulose/mannitol ratio was increased significantly in Crohn's disease patients vs. their relatives [0.03 (0.01-0.24) vs. 0.01 (0.003-0.19), P=0.005]. The percentage of abnormal tests was significantly higher in familial vs. sporadic first-degree relatives of Crohn's disease patients (29% vs. 11%, P=0.0281). Abnormal permeability occurred significantly more frequent in patients with familial Crohn's disease carrying the frameshift mutation. The frameshift mutation 3020 insC was associated with increased permeability in 75% in the multiplex and in 61% of the sporadic CD patients. One partner had abnormal lactulose/mannitol ratio. Conclusion Intestinal permeability is raised in Crohn's disease patients and relatives, with higher rates in familial vs. sporadic healthy relatives. CARD15 mutations are associated with abnormal permeability in ileal Crohn's disease.

Distribution of common CARD15 variants in patients with sporadic Crohn's disease: cases from Turkey

Three common genetic variations, namely, R702W, G908R, and 1007fs, on CARD15 have been shown to increase the risk for Crohn's disease (CD) in Caucasian populations. In this study the frequencies of these CARD15 variants were determined by genotyping in 56 patients with CD and 100 healthy ethnically matched controls from Turkey. Overall frequency of all three variants was 10.7% in CD patients, compared with 1.5% in controls (odds ratio [OR]: 7.9). Among them, the frequency of the G908R variant allele was 8% in CD cases, compared with 0% in controls (OR: 36.8). The allele frequencies of three CD-related CARD15 variants were considerably lower in the control group compared to the reported Caucasian populations. Among the described CARD15 variants, G908R confers an increased susceptibility to CD, whereas the more frequently reported associations in Europeans with R702W and 1007fs are not confirmed in this Turkish population.

Intestinal permeability and genetic determinants in patients, first-degree relatives, and controls in a high-incidence area of Crohn's disease in Southern Italy

OBJECTIVE

A defect of gastrointestinal barrier function is considered to represent an important step in the pathogenesis of Crohn's disease (CD) but the mechanisms leading to an increased intestinal permeability (IP) are poorly understood. Since IP is influenced by pro-inflammatory mediators, it seems likely that a genetically determined abnormal immune response may lead to a loss of barrier function.

METHODS

In a geographic area in Southern Italy with high incidence of CD we investigated IP (lactulose/mannitol testing) together with the three main mutations of the NOD2/CARD15 and the D299G polymorphism of the toll-like receptor (TLR)-4 gene in 23 families of CD patients (patients and first-degree relatives).

RESULTS

Forty-eight percent of CD patients and 40% of their healthy relatives were found to have an abnormal IP compared to 5% of an appropriate control population (p < 0.0001). IP, however, was not associated with the L1007finsC mutation of the NOD2/CARD15 or the D299G variant of the TLR-4 gene. Allele frequency of the only L1007finsC mutation of CARD15 was significantly increased in patients (8.7%, p < 0.003) and in relatives (8.3%, p < 0.024) compared with controls (2.4%), whereas the D299G variant of the TLR-4 gene was found to be increased only in relatives (8.3%, p < 0.022), but not in patients (4.3%) compared with the control population (1.7%).

CONCLUSIONS

There was no association between IP and genetic markers. Our findings showed a very high proportion of healthy first-degree relatives to bare alterations suggested to constitute determinants of CD. Mutations of NOD2/CARD15 or TLR-4, however, do not lead to permeability defects emphasizing the importance of additional environmental and/or genetic factors for pathogenesis.

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.

Toll-like receptor 4 and NOD2/CARD15 mutations in Hungarian patients with Crohn's disease: phenotype-genotype correlations

AIM

To determine common NOD2/CARD15 mutations and TLR4 D299G polymorphism in Hungarian patients with CD.

METHODS

A total of 527 unrelated patients with CD (male/female: 265/262, age: 37.1 (SD 7.6) years) and 200 healthy subjects were included. DNA was screened for possible NOD2/CARD15 mutations by denaturing high-performance liquid chromatography (confirmed by direct sequencing). TLR4 D299G was tested by PCR-RFLP.

RESULTS

NOD2/CARD15 mutations were found in 185 patients (35.1%) and in 33 controls (16.5%, P<0.0001). SNP8/R702W (10.8% vs 6%, P = 0.02), SNP13/3020insC (19.4% vs 5%, P<0.0001) and exon4 R703C (2.1% vs 0%, P = 0.02) mutations were more frequent in CD, while the frequency of SNP12/G908R was not increased. The frequency of TLR4 D299G was not different (CD: 9.9% vs controls: 12.0%). Variant NOD2/CARD15 allele was associated with an increased risk for CD (OR(het) = 1.71, 95%CI = 1.12-2.6, P = 0.0001, OR(two-risk alleles) = 25.2, 95%CI = 4.37-8, P<0.0001), early disease onset (carrier: 26.4 years vs non-carrier: 29.8 years, P = 0.0006), ileal disease (81.9% vs 69.5%, OR = 1.99, 95%CI = 1.29-3.08, P = 0.02, presence of NOD2/CARD15 and TLR4: 86.7% vs 64.8%), stricturing behavior (OR = 1.69, 95%CI = 1.13-2.55, P = 0.026) and increased need for resection (OR=1.71, 95%CI: 1.13-2.62, P = 0.01), but not with duration, extra-intestinal manifestations, familial disease or smoking. TLR4 exhibited a modifier effect: age of onset in wt/TLR4 D299G carriers: 27.4 years vs NOD2mut/TLR D299G: 23 years (P = 0.06), in NOD2mut/wt: 26.7 years.

CONCLUSION

These results confirm that variant NOD2/CARD15 (R702W, R703C and 3020insC) alleles are associated with earlier disease onset, ileal disease, stricturing disease behavior in Hungarian CD patients. In contrast, although the frequency of TLR4 D299G polymorphism was not different from controls, NOD2/TLR4 mutation carriers tended to present at earlier age.

Toll-like receptor 4 and NOD2/CARD15 mutations in Hungarian patients with Crohn’s disease: Phenotype-genotype correlations

AIM: To determine common NOD2/CARD15 mutations and TLR4 D299G polymorphism in Hungarian patients with CD.

METHODS: A total of 527 unrelated patients with CD (male/female: 265/262, age: 37.1 (SD 7.6) years) and 200 healthy subjects were included. DNA was screened for possible NOD2/CARD15 mutations by denaturing high-performance liquid chromatography (confirmed by direct sequencing). TLR4 D299G was tested by PCR-RFLP.

RESULTS: NOD2/CARD15 mutations were found in 185 patients (35.1%) and in 33 controls (16.5%, P<0.0001). SNP8/R702W (10.8% vs 6%, P = 0.02), SNP13/3020insC (19.4% vs 5%, P<0.0001) and exon4 R703C (2.1% vs 0%, P = 0.02) mutations were more frequent in CD, while the frequency of SNP12/G908R was not increased. The frequency of TLR4 D299G was not different (CD: 9.9% vs controls: 12.0%). Variant NOD2/CARD15 allele was associated with an increased risk for CD (OR_het = 1.71, 95%CI = 1.12-2.6, P = 0.0001, OR_{two-risk alleles} = 25.2, 95%CI = 4.37-∞, P<0.0001), early disease onset (carrier: 26.4 years vs non-carrier: 29.8 years, P = 0.0006), ileal disease (81.9% vs 69.5%, OR = 1.99, 95%CI = 1.29-3.08, P = 0.02, presence of NOD2/CARD15 and TLR4: 86.7% vs 64.8%), stricturing behavior (OR = 1.69, 95%CI = 1.13-2.55, P = 0.026) and increased need for resection (OR=1.71, 95%CI: 1.13-2.62, P = 0.01), but not with duration, extra-intestinal manifestations, familial disease or smoking. TLR4 exhibited a modifier effect: age of onset in wt/TLR4 D299G carriers: 27.4 years vs NOD2mut/TLR D299G: 23 years (P = 0.06), in NOD2mut/wt: 26.7 years.

CONCLUSION: These results confirm that variant NOD2/CARD15 (R702W, R703C and 3020insC) alleles are associated with earlier disease onset, ileal disease, stricturing disease behavior in Hungarian CD patients. In contrast, although the frequency of TLR4 D299G polymorphism was not different from controls, NOD2/TLR4 mutation carriers tended to present at earlier age.

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.

Differential effects of NOD2 variants on Crohn's disease risk and phenotype in diverse populations: a metaanalysis

OBJECTIVES

Three variants of the CARD15/NOD2 gene (SNP8, SNP12, and SNP13) have been associated with Crohn's disease (CD). We assessed the impact of NOD2 variants on the CD risk across diverse populations and examined possible associations with disease phenotype.

METHODS

We performed a metaanalysis searching MEDLINE and EMBASE (last search 05/2004) and contacting field experts.

RESULTS

Forty-two eligible studies contributed data on 206 comparisons. No variants were detected in Asians. In non-Jewish descent Caucasians carriage of SNP8, SNP12, or SNP13 had an odds ratio (OR) for CD of 2.20 (95% CI: 1.84-2.62), 2.99 (95% CI: 2.38-3.74), and 4.09 (95% CI: 3.23-5.18), respectively. For Jewish descent patients the corresponding ORs were 1.74, 1.93, and 2.45, respectively. The OR in carriers of at least two alleles was 17.1 (95% CI: 10.7-27.2). Large studies tended to yield more conservative estimates than smaller studies, so publication or other bias cannot be excluded. Among CD patients, carrying at least one high-risk variant increased slightly the risk for familial disease (OR = 1.49, (95% CI: 1.18-1.87)), modestly the risk of stenosing CD (OR = 1.94, (95% CI: 1.61-2.34)), and more prominently the risk of small bowel involvement (OR = 2.53, (95% CI: 2.01-3.16)).

CONCLUSIONS

SNP8, SNP12, and SNP13 have differential effects on CD risk, with SNP13 having the strongest genetic effect. These NOD2 variants are also significant risk factors for CD phenotype, in particular ileal location.