Inflammatory bowel disease. II. Gene mapping

Polymorphisms of PTPN11 coding SHP-2 as biomarkers for ulcerative colitis susceptibility in the Japanese population

OBJECTIVE

To identify genetic determinants of inflammatory bowel disease (IBD), we examined an association between polymorphisms of both the programmed cell death 1 gene (PDCD1) and the src homology 2 domain-containing tyrosine phosphatase 2 gene (PTPN11) and susceptibility to IBD.

METHODS

Study subjects comprised 114 patients with ulcerative colitis (UC), 83 patients with Crohn's disease, and 200 healthy control subjects. Five single nucleotide polymorphisms (SNPs) in PDCD1 and PTPN11 were detected by polymerase chain reaction restriction fragment length polymorphism. Subsequently, haplotypes composed of the two SNPs in PTPN11 were constructed.

RESULTS

The frequencies of the Hap 1 haplotype and its homozygous Hap 1/Hap 1 diplotype of PTPN11 were significantly increased in UC patients compared to control subjects (P = 0.011 and P = 0.030, respectively). While no association was found for PDCD1 for UC or CD and none for PTPN11 for CD.

CONCLUSION

PTPN11 is a genetic determinant for the pathogenesis of UC, and haplotyping of PTPN11 may be useful as a genetic biomarker to identify high-risk individuals susceptible to UC.

No association of the cytotoxic T-lymphocyte associated gene CTLA4 +49A/G polymorphisms with Crohn’s disease and ulcerative colitis in Hungarian population samples

AIM: The goal of the current work was to analyse the prevalence of the +49A/G variant of the cytotoxic T-lymphocyte antigen 4 gene (CTLA4) in Hungarian patients with Crohn’s disease (CD) and ulcerative colitis (UC).

METHODS: A total of 130 unrelated subjects with CD and 150 with UC, and 170 matched controls were genotyped for the single nucleotide polymorphism (SNP). The genotypes were determined by using PCR/RFLP test.

RESULTS: The G allele frequency and the prevalence of the GG genotype were 38.1% and 12.3% in the CD group, 40.6% and 18.6% in the UC patients, and 37.4% and 15.9% in the control group, respectively.

CONCLUSION: The results of the current study show that carriage of the +49G SNP in heterozygous or in homozygous form does not confer risk either for CD or for UC in the Hungarian population.

Prevalence of SLC22A4 1672T and SLC22A5 −207C combination defined TC haplotype in Hungarian ulcerative colitis patients

Ulcerative colitis (UC) is a chronic inflammatory disease of the gastrointestinal tract. The aim of this study was to verify the prevalence rate of the haplotype called TC, determined by combination of two functional alleles of OCTN cation transporter genes (SLC22A4 1672T and SLC22A5 -207C combination variants) in ulcerative colitis patients and unrelated healthy controls. The "TC haplotype" has recently been suggested to confer risk for UC. A total of 121 unrelated Hungarian subjects with UC and 110 matched controls were genotyped for the two single nucleotide polymorphisms. The genotypes were determined by using PCR/RFLP assay and direct sequencing. The SLC22A4 1672T allele frequency was 46.7% in the patients with UC and 46.4% in the controls, whereas the SLC22A5 -207C allele occurred in 48.8% of the patients and 51.4% of the controls. The prevalence of the TC haplotype was 19% in the patient group and 22.7% in controls. Since there was no accumulation of the TC haplotype in the patient group, our observation suggests that carrying the TC haplotype is not associated with a higher risk for UC in the Hungarian population.

Familial expression of anti-Escherichia coli outer membrane porin C in relatives of patients with Crohn's disease

BACKGROUND & AIMS

Crohn's disease (CD) is a genetically complex disorder with strong familial aggregation. Pathogenesis appears to involve dysregulation of the immune response to endogenous bacteria. Anti-Escherichia coli outer membrane porin C (anti-OmpC) expression reflects an exaggerated response to commensal bacteria and occurs with higher frequency in CD. The aim of this study was to determine whether there is familial aggregation and genetic determination of anti-OmpC expression in CD families.

METHODS

Study groups consisted of 787 CD patients, 389 ulcerative colitis (UC) patients, 619 unaffected relatives, and 216 healthy controls. Serum anti-OmpC was detected by enzyme-linked immunosorbent assay.

RESULTS

CD patients had a greater percentage of anti-OmpC than UC patients and healthy controls. Anti-OmpC expression was more frequent in unaffected relatives from CD-only or mixed families, compared with healthy controls (P = .002 and .0001, respectively), and it was more frequent in UC patients from mixed families than those from UC-only families (P = .02). There was a significant familiality in anti-OmpC expression: P = .02 for qualitative concordance and P < .0001 for quantitative intraclass correlation. The heritability estimate for anti-OmpC level was .39 (P < .0001).

CONCLUSIONS

Anti-OmpC is a heritable immunophenotype. Increased anti-OmpC expression in the unaffected family members of CD patients suggests that anti-OmpC may be an immunologic risk marker for CD. That UC patients in mixed families had a higher response to OmpC than those in UC-only families indicates pathophysiologic heterogeneity within UC.

Analysis of cytotoxic T lymphocyte associated antigen 4 gene polymorphisms in patients with ulcerative colitis

BACKGROUND AND AIM

Ulcerative colitis (UC) is a multifactorial disease associated with dysregulated immunity. Recently, cytotoxic T lymphocyte associated antigen 4 (CTLA-4) gene polymorphisms have been reported in association with several autoimmune diseases in several populations. In the present study, the possible implication of the CTLA-4 gene as a risk factor for UC in the Iranian population was investigated.

METHODS

One hundred UC patients and 100 healthy subjects were studied. CTLA-4 exon 1 position 49 (A/G: codon 17: Thr/Ala) polymorphisms were investigated by polymerase chain reaction single strand confirmation polymorphism method. Four of the patients and one of the healthy controls were excluded from the study because of incomplete DNA extraction.

RESULTS

The allele frequencies of A and G in 96 patients (A: 66.1%; G: 33.9%) were not significantly different from the 99 control subjects (A: 63.1%; G: 36.9%, P > 0.05). No significant differences in the distribution of genotype frequencies were observed between A + 49G gene polymorphisms and UC in the Iranian population (P > 0.05).

CONCLUSION

CTLA-4 polymorphism is not associated with UC in the Iranian population.

Crohn’s disease in Japanese is associated with a SNP-haplotype of N-acetyltransferase 2 gene

AIM: To investigate the frequency and distribution of N-acetyltransferase 2 (NAT2) and uridine 5’-diphosphate (UDP)-glucuronosyltransferase 1A7 (UGT1A7) genes in patients with ulcerative colitis (UC) and Crohn’s disease (CD).

METHODS: Frequencies and distributions of NAT2 and UGT1A7 SNPs as well as their haplotypes were investigated in 95 patients with UC, 60 patients with CD, and 200 gender-matched, unrelated, healthy, control volunteers by PCR-restriction fragment length polymorphism (RFLP), PCR-denaturing high-performance liquid chromatography (DHPLC), and direct DNA sequencing.

RESULTS: Multiple logistic regression analysis revealed that the frequency of haplotype, NAT2*7B, significantly increased in CD patients, compared to that in controls (P = 0.0130, OR = 2.802, 95%CI = 1.243-6.316). However, there was no association between NAT2 haplotypes and UC, or between any UGT1A7 haplotypes and inflammatory bowel disease (IBD).

CONCLUSION: It is likely that the NAT2 gene is one of the determinants for CD in Japanese. Alternatively, a new CD determinant may exist in the 8p22 region, where NAT2 is located.

Association of polymorphic alleles of CTLA4 with inflammatory bowel disease in the Japanese

AIM: To examine an association between the cytotoxic T-lymphocyte antigen 4 (CTLA4) gene that plays a role in downregulation of T-cell activation and inflammatory bowel disease consisting of ulcerative colitis (UC) and Crohn’s disease (CD) in the Japanese.

METHODS: We studied 108 patients with UC, 79 patients with CD, and 200 sex-matched healthy controls, with respect to three single nucleotide polymorphisms (SNPs) in CTLA4, such as C-318T in the promoter region, A+49G in exon 1 and G+6230A in the 3’ untranslated region (3’-UTR) by a PCR-restriction fragment length polymorphism method, and to an (AT)_n repeat polymorphism in 3’-UTR by fragment analysis with fluorescence-labeling on denaturing sequence gels. Frequency of alleles and genotypes and their distribution were compared statistically between patients and controls and among subgroups of patients, using χ² and Fisher exact tests.

RESULTS: The frequency of “A/A” genotype at the G+6230A SNP site was statistically lower in UC patients than in controls (3.7% vs 11.0%, P = 0.047, odds ratio (OR = 0.311). Moreover, the frequency of “G/G” genotype at the A+49G SNP site was significantly higher in CD patients with fistula (48.6%) than those without it (26.2%) (P = 0.0388, OR=2.67).

CONCLUSION: The results suggest that CTLA4 located at 2q33 is a determinant of UC and responsible for fistula formation in CD in the Japanese.

A genetic contribution to inflammatory bowel disease in Iceland: a genealogic approach

BACKGROUND AND AIMS

Both genetic and environmental factors play a role in the development of Crohn's disease (CD) and ulcerative colitis (UC), collectively known as inflammatory bowel disease (IBD). The aim of this study was to estimate the genetic component in IBD in Iceland.

METHODS

A population-based sample, representing everyone diagnosed with IBD in Iceland from 1950 to 1996, was studied using a computerized population-wide genealogic database. The relationships among the patients were analyzed by calculating the kinship coefficient and the relative risk.

RESULTS

The kinship coefficients for the patients were significantly greater than the mean kinship coefficient for the controls ( P < 10 -6 ). The risk ratio for siblings of IBD, UC, and CD patients was 5.0 ( P < 0.001), 5.9 ( P < 0.001), and 4.1 ( P = 0.033), respectively. The cross-risk ratio for siblings of UC patients developing CD (or vice versa) was 2.6 ( P = 0.015).

CONCLUSIONS

The results indicate that the IBD patients are more closely related than the controls, which strongly supports the involvement of a genetic component in the development of IBD in Icelandic patients. We find that the increase in risk for relatives of UC probands to develop UC, or relatives of CD probands to develop CD, is greater than the increase in risk for relatives of UC probands to develop CD, or relatives of CD probands to develop UC.

Genetic polymorphisms of the human MDR1 drug transporter

P-glycoprotein is an ATP-dependent efflux pump that contributes to the protection of the body from environmental toxins. It transports a huge variety of structurally diverse compounds. P-glycoprotein is involved in limiting absorption of xenobiotics from the gut lumen, in protection of sensitive tissues (brain, fetus, testis), and in biliary and urinary excretion of its substrates. P-glycoprotein can be inhibited or induced by xenobiotics, thereby contributing to variable drug disposition and drug interactions. Recently, several SNPs have been identified in the MDR1 gene, some of which can affect P-glycoprotein expression and function. Potential implications of MDR1 polymorphisms for drug disposition, drug effects, and disease risk are discussed.

Association between the C3435T MDR1 gene polymorphism and susceptibility for ulcerative colitis

BACKGROUND & AIMS

The human multidrug resistance 1 (MDR1) gene product P-glycoprotein is highly expressed in intestinal epithelial cells, where it constitutes a barrier against xenobiotics. The finding that mdr1a knockout mice develop a form of colitis that is similar to ulcerative colitis, which can be prevented by antibiotics, indicates a barrier function for P-glycoprotein against the invasion of bacteria or toxins. Because the MDR1 single nucleotide polymorphism C3435T is associated with lower intestinal P-glycoprotein expression, we tested whether this polymorphism predisposes to development of ulcerative colitis.

METHODS

Allele frequencies and genotype distributions of the C3435T single nucleotide polymorphism were investigated in 149 patients with ulcerative colitis, 126 patients with Crohn's disease, and sex-matched healthy controls.

RESULTS

Significantly increased frequencies of the 3435T allele and the 3435TT genotype were observed in patients with ulcerative colitis compared with controls (3435T: P = 0.049; odds ratio, 1.4; 95% confidence interval, 1.02-1.94; 3435TT: P = 0.045; odds ratio, 2.03; 95% confidence interval, 1.04-3.95). In contrast, frequencies of the T allele and the TT genotype were the same in patients with Crohn's disease as in controls (P = 0.66 and P = 0.59, respectively). In comparison to 998 non-sex-matched controls, the effect for the TT genotype in ulcerative colitis patients was more pronounced (P = 0.0055; odds ratio, 2.1).

CONCLUSIONS

The higher frequency of the 3435TT genotype in patients with ulcerative colitis corroborates the findings from the mdr1a knockout mice. The results support the notion that P-glycoprotein plays a major role in the defense against intestinal bacteria or toxins. Impairment of barrier function in 3435TT subjects could render this genotype more susceptible to the development of ulcerative colitis.