Contribution of IL23R but not ATG16L1 to Crohn's disease susceptibility in Koreans

Association of FCGR2A, JAK2 or HNF4A variants with ulcerative colitis in Koreans

BACKGROUND

Recent genome-wide association studies have identified over 40 candidate genes contributing to ulcerative colitis susceptibility. The goal of this study was to test the reported ulcerative colitis susceptibility genes including FCGR2A, SLC26A3, JAK2 and HNF4A in Korean patients with ulcerative colitis and Crohn's disease.

METHODS

Five single nucleotide polymorphisms from 4 loci including FCGR2A, SLC26A3, JAK2 and HNF4A were genotyped in 661 patients with ulcerative colitis, 642 patients with Crohn's disease and 601 healthy controls.

RESULTS

Statistically significant associations with ulcerative colitis were found at FCGR2A (rs1801274, p=2.3×10(-4), OR=0.70 (95% CI=0.57-0.84) under the allelic model), the JAK2 locus (rs10975003, p=6.7×10(-4), OR=1.43 (95% CI=1.16-1.77) under the allelic model) and HNF4A (rs6017342, p=0.002, OR=0.66 (95% CI=0.51-0.85) under the allelic model). The association of FCGR2A was much stronger in female patients with ulcerative colitis (p=5.7×10(-6)) than in males (p=0.50). Except rs10975003 from the JAK2 locus, none showed positive association with Crohn's disease.

CONCLUSIONS

Our data suggest that FCGR2A, JAK2 or HNF4A variants play a role in the pathogenesis of ulcerative colitis in Koreans.

Genome-wide association studies and Crohn's disease

The development of genome-wide association scanning (GWAS) has revolutionized the search for genetic loci associated with complex diseases. Crohn's disease (CD), together with ulcerative colitis, has been a principal beneficiary of this technology with a recent meta-analysis from the International IBD Genetics Consortium increasing the number of confirmed CD susceptibility loci to 71. When one considers that prior to the development of GWAS only three susceptibility loci had been identified, the degree of progress becomes obvious. In this article we will summarize the principal discoveries that have been made in CD genetics and explain how these have contributed to our improved understanding of disease pathogenesis.

A hospital-based study of clinical and genetic features of Crohn's disease

BACKGROUND/PURPOSE

The aim of this study was to gain a better understanding of the current incidence of Crohn's disease (CD) in Taiwan and examine its clinical/genetic characteristics because there has been a trend toward increased diagnosis in the Asia-Pacific area. The genetic background seen in CD cases in Taiwan seems to be different from that in Western countries.

METHODS

By reviewing the database in the National Taiwan University Hospital, CD patients were identified by clinical, endoscopic, and imaging findings. The clinical characteristics were recorded and analyzed. DNA was extracted from the peripheral blood of patients after obtaining informed consent. Polymerase chain reaction was performed with specific primers followed by direct sequencing to determine the single-nucleotide polymorphisms ATG16L1, CCR6, IL12B, IL23R, LRRK2, TNFSF2, and TNFSF15 CD-associated genes.

RESULTS

Clinical data from 110 CD patients were examined from 1988 to 2008, with a mean follow-up period of 4.5 years. There was a marked increase in new CD diagnosis, especially after 2004. Among the 110 patients, 71 men and 39 women, the age at diagnosis was 30.5±17.8 years (mean±standard deviation). Stenosis occurred in 33.6% (37 of 110) and 40.9% (45 of 110) of patients who underwent surgery. The mortality rate was 2.7%, all because of sepsis. Genetic analysis of 39 patients showed that ATG16L1 and TNFSF15 were associated with susceptibility to CD in Taiwan.

CONCLUSION

Recently, the incidence of CD diagnosis in Taiwan has markedly increased. ATG16L1 and TNFSF15 are associated with CD in Taiwan.

Recent insights into the genetics of inflammatory bowel disease

Inflammatory bowel diseases (IBDs) are complex, multifactorial disorders that comprise Crohn's disease (CD) and ulcerative colitis (UC). Genome-wide association studies have identified approximately 100 loci that are significantly associated with IBD. These loci implicate a diverse array of genes and pathophysiologic mechanisms, including microbe recognition, lymphocyte activation, cytokine signaling, and intestinal epithelial defense. Consistent with epidemiologic predictions, many IBD-associated loci demonstrate genome-wide significant associations to both CD and UC, notably, genes whose products function in the interleukin-23 pathway, and transcription factors, including NK2 transcription factor related, locus 3 (NKX2-3), SMAD3, STAT3, ZMIZ1, and c-REL. Although CD and UC are both associated with genomic regions that implicate products of genes involved in leukocyte trafficking, there is evidence for association patterns that are distinct between CD and UC. CD-predominant associations include NOD2 and genes that regulate autophagy. In UC, the predominant association signal is on chromosome 6p21, in the major histocompatibility complex region, near HLA class II genes. UC-predominant loci have also implicated genes mediating epithelial defense function. There is a striking overlap of loci between diseases, which could provide comparative insight into mechanisms of disease pathogenesis. Genes that encode factors that function in the interleukin-23 pathway have been associated with a number of chronic inflammatory diseases, notably psoriasis and ankylosing spondylitis. Distinct genetic associations indicate that the colitis associated with primary sclerosing cholangitis is pathophysiologically distinct from UC that is not associated with primary sclerosing cholangitis. As many as 14 susceptibility loci are shared between IBD and celiac disease, indicating significant overlap in pathophysiology. Future genetic studies will be directed toward identifying uncommon variations with potentially greater statistical effects, defining population differences, and more completely accounting for familial transmission of disease.

An investigation of genome-wide studies reported susceptibility loci for ulcerative colitis shows limited replication in north Indians

Genome-Wide Association studies (GWAS) of both Crohn's Disease (CD) and Ulcerative Colitis (UC) have unearthed over 40 risk conferring variants. Recently, a meta-analysis on UC revealed several loci, most of which were either previously associated with UC or CD susceptibility in populations of European origin. In this study, we attempted to replicate these findings in an ethnically distinct north Indian UC cohort. 648 UC cases and 850 controls were genotyped using Infinium Human 660W-quad. Out of 59 meta-analysis index SNPs, six were not in the SNP array used in the study. Of the remaining 53 SNPs, four were found monomorphic. Association (p<0.05) at 25 SNPs was observed, of which 15 were CD specific. Only five SNPs namely rs2395185 (HLA-DRA), rs3024505 (IL10), rs6426833 (RNF186), rs3763313 (BTNL2) and rs2066843 (NOD2) retained significance after Bonferroni correction. These results (i) reveal limited replication of Caucasian based meta-analysis results; (ii) reiterate overlapping molecular mechanism(s) in UC and CD; (iii) indicate differences in genetic architecture between populations; and (iv) suggest that resources such as HapMap need to be extended to cover diverse ethnic populations. They also suggest a systematic GWAS in this terrain may be insightful for identifying population specific IBD risk conferring loci and thus enable cross-ethnicity fine mapping of disease loci.

Association of CARD8 with inflammatory bowel disease in Koreans

Caspase recruitment domain (CARD)-containing protein 8 (CARD8) is a potential candidate risk gene for inflammatory bowel disease (IBD) because of its role as a component of the NALP3 inflammasome and as an inhibitor of nuclear factor-kappa B. Previous studies examining the association of a CARD8 single-nucleotide polymorphism (SNP) (rs2043211, p.Cys10X) with IBD yielded mixed results in Caucasians that may result from interaction with NALP3 or NOD2 (nucleotide-binding oligomerization domain 2) variants. To understand the genetic association between CARD8/NALP3 and IBD in Koreans, we investigated seven CARD8, four NALP3 and four NOD2 SNPs in 650 Crohn's disease (CD), 660 ulcerative colitis (UC) patients and 688 controls from the Korean population. rs2043211 of CARD8 showed significant association with UC (P = 0.011; odds ratio = 1.50, 95% confidence intervals = 1.12-2.00, P = 0.006 under recessive model). In contrast, an SNP in intron 1, rs1972619, was associated with CD only (P = 0.033). None of the NALP3 or NOD2 SNPs was significantly associated with CD or UC in the Korean populations. The stop allele of rs2043211 was associated with higher serum interleukin-1β levels only in female patients with UC (P = 0.027). Our data suggest that CARD8 variants might have roles in the pathogenesis of CD and UC in Koreans.

Effect of cytotoxic T lymphocyte-associated molecule 4 1661 gene polymorphism on its expression and transcription in ulcerative colitis

OBJECTIVE

Our aim was to investigate the expression of cytotoxic T lymphocyte-associated molecule 4 (CTLA-4) in ulcerative colitis (UC) and to evaluate the effect of CTLA-4 gene -1661A/G polymorphism on CTLA-4 expression and transcription.

METHODS

A total of 20 UC patients and 22 healthy controls matched by age and sex were enrolled at Zhongnan Hospital of Wuhan University in central China. The CTLA-4 -1661A/G polymorphism was genotyped by the polymerase chain reaction-restriction fragment length polymorphism method. A Western blot analysis was performed to determine the full length CTLA-4 (flCTLA-4) protein expression in the peripheral blood of the UC patients. Serum-soluble CTLA-4 (sCTLA-4) levels were measured by enzyme-linked immunosorbent assay. CTLA-4-1661G mutant promoter transcription function was analyzed by site-directed PCR-based mutagenesis.

RESULTS

CTLA-4 protein expression on CD4(+) T cells in UC patients was lower than that in the healthy controls (P < 0.001) while serum sCTLA-4 in the UC patients was significantly higher than that in the healthy controls (P < 0.001). No correlation was found between flCTLA-4 and sCTLA-4 expression levels and the -1661 A/G polymorphism of the CTLA-4 gene. Meanwhile, CTLA-4 -1661 allele A had no significant impact on the promoter activity compared with allele G (P > 0.05).

CONCLUSION

CTLA-4 expressions were aberrant in UC patients compared with the healthy controls. CTLA-4 -1661A/G polymorphism had no significant impact on CTLA-4 expression and transcription in the peripheral CD4 T cells of UC patients.

Clinical features and long-term prognosis of Crohn's disease in Korea

OBJECTIVE

Recent studies have suggested that the clinical characteristics and genetic background of Crohn's disease (CD) patients differ between Asian and Caucasian individuals. However, the clinical features and course of CD in Asian patients remain unclear. Therefore, we investigated the clinical features and long-term prognosis of CD in a Korean population.

MATERIAL AND METHODS

We retrospectively analyzed 278 Korean patients with CD first diagnosed at the Asan Medical Center between March 1991 and February 2007.

RESULTS

The male-to-female ratio was 2.2:1 and the median age at diagnosis was 23 years. The median duration of follow-up was 71 months (range, 1-210 months). At diagnosis, 187 patients (67.3%) had disease in both small bowel and colon, 68 (24.4%) had isolated small bowel disease, and 23 (8.3%) had isolated colonic disease. The number of patients with stricturing or penetrating behavior as defined by the Montreal classification increased from 87 (31.3%) at diagnosis to 141 (50.7%) at final evaluation. One hundred and thirty patients (46.8%) experienced perianal fistulas before and/or after diagnosis of CD. A total of 71 patients (25.5%) underwent intestinal resection and the cumulative probability of intestinal resection after 1, 5, and 10 years was 15.5%, 25.0%, and 32.8%, respectively.

CONCLUSIONS

Korean CD patients differed from Western patients in gender distribution, disease location, and perianal fistula occurrence. Korean CD patients may also have better clinical courses than Western patients, as indicated by the lower intestinal resection rate.

[A case of ulcerative colitis found in a patient whose parent has Crohn's disease]

Inflammatory bowel diseases (IBD) is heterogeneous, chronic relapsing disorder. Inappropriate and exaggerated immune response for the luminal antigen is known as a main pathogenesis. Genetic, infectious, and environmental factors are responsible for unbalanced immune response, but the definite pathogenesis is still unclear. Genetic factor is the most important role of all. That is based on high concordance rate of identical twins and family history. The incident rate and prevalence of IBD for the Asian population is relatively lower than Western population, and the lack of NOD2 or TLR4 genetic polymorphisms in Korea and Japanese population suggests the difference in genetic background between Asian and Western population. In Korea, the case of familial aggregation of IBD is pretty rare. We report a case of the daughter with ulcerative colitis and her mother with Crohn's disease who have a -159C/T promoter polymorphism of CD14 gene for IBD.

T300A polymorphism of ATG16L1 and susceptibility to inflammatory bowel diseases: A meta-analysis

AIM: To evaluate the association of the autophagy-related 16-like 1 (ATG16L1) T300A polymorphism (rs2241880) with predisposition to inflammatory bowel diseases (IBD) by means of meta-analysis.

METHODS: Publications addressing the relationship between rs2241880/T300A polymorphism of ATG16L1 and Crohn’s disease (CD) and ulcerative colitis (UC) were selected from the MEDLINE and EMBASE databases. To make direct comparisons between the data collected in these studies, the individual authors were contacted when necessary to generate a standardized set of data from these studies. From these data, odds ratio (OR) with 95% confidence interval (CI) were calculated.

RESULTS: Twenty-five studies of CD were analyzed, 14 of which involved cases of UC. The variant G allele of ATG16L1 was positively associated with CD (OR = 1.32, 95% CI: 1.26-1.39, P < 0.00001) and UC (OR = 1.06, 95% CI: 1.01-1.10, P = 0.02). For child-onset IBD, a higher G allele frequency was found for cases of CD (OR = 1.35, 95% CI: 1.16-1.57, P = 0.0001) than for cases of UC (OR = 0.98, 95% CI: 0.81-1.19, P = 0.84) relative to controls.

CONCLUSION: The ATG16L1 T300A polymorphism contributes to susceptibility to CD and UC in adults, but different in children, which implicates a role for autophagy in the pathogenesis of IBD.

Inflammatory bowel disease in Korea: epidemiological, genomic, clinical, and therapeutic characteristics

Inflammatory bowel disease (IBD) describes chronic inflammatory disease of the intestines and has a variable course; Crohn's disease and ulcerative colitis comprise the two main forms of the condition. Although IBD occurs worldwide, its epidemiologic and clinical characteristics vary depending upon the geographic location and the ethnicity of the population. Identifying the characteristic features of IBD in populations living in different geographical locations and with different ethnicities may provide significant clues about its etiology and pathophysiology, which in turn may be helpful in the development of more appropriate treatment strategies for IBD for these different populations. Therefore, it is important for each country and region to evaluate critically the epidemiology, genomics, and clinical characteristics of IBD among its own population. We have performed a critical review of the recent data in Korea, and describe herein the current epidemiologic and genotypic status, as well as the clinical manifestations and therapeutic responses of IBD that are unique to Korean patients.

Association of signal transducer and activator of transcription 4 genetic variants with extra-intestinal manifestations in inflammatory bowel disease

AIMS

The STAT4 gene encodes a transcription factor which plays an important role in the development of inflammation of many immune-mediated diseases. We investigated the relationship between STAT4 single nucleotide polymorphisms (SNPs) and susceptibility to ulcerative colitis (UC) and Crohn's disease (CD) and disease phenotypes in the Korean population.

MAIN METHODS

We performed a case-control association study in individuals with UC (N=246), CD (N=182), and healthy controls (N=229).

KEY FINDINGS

We genotyped 8 STAT4 SNPs (rs11889341, rs7574865, rs8179673, rs6752770, rs925847, rs10168266, rs10181656, and rs11685878) in the STAT4 gene in patients and controls. SNP rs925847 in the STAT4 gene was significantly associated with susceptibility to UC (P=0.025; OR=0.63) in dominant genotype analysis, though none of these SNPs were associated with CD susceptibility. Moreover, a significant association was identified between SNP rs11889341 and joint involvement (P=0.040; OR=3.79), and between SNP rs925847 and eye involvement (P=0.030; OR=2.42) in UC patients. For CD, rs925847 genetic variant was associated with joint (P=0.029; OR=3.93) and perianal lesions (P=0.033; OR=2.27).

SIGNIFICANCE

Our data demonstrated that the STAT4 genetic variants could predispose an individual to IBD and its extra-intestinal ailments in Koreans, suggesting the common pathogenesis of IBD (especially, extra-intestinal manifestations) and other autoimmune diseases.

[A case of monozygotic twins with Crohn's disease]

Although the incidence and prevalence rates of IBD in Korea are still lower than Western populations, they have been increasing rapidly during the past decades. Crohn's disease (CD) tends to run in families because it is thought to be related to genetic susceptibility coupled with environmental factors. A large number of monozygotic and dizygotic twin pairs with inflammatory bowel disease have been reported in western countries. The population relative risk in first-degree relatives is considered to be about equal in both Koreans and westerners. To our best knowledge, there is no report in monozygotic twins with CD in Korea. This case report is the first documented occurrence of concordant CD occurring in monozygotic twins in Korea.