Lack of association of ACP1 gene with inflammatory bowel disease: a case-control study

The red cell acid phosphatease (ACP1) gene, which encodes a low molecular weight phosphotyrosine phosphatase (LMW-PTP), has been suggested as a common genetic factor of autoimmunity. In the present study, we aimed to investigate the possible influence of ACP1 polymorphisms in the susceptibility of inflammatory bowel disease (IBD). A total of 1271 IBD Spanish patients [720 Crohn's disease (CD) and 551 ulcerative colitis (UC)] and 1877 healthy subjects were included. Four single-nucleotide polymorphisms (SNPs), rs10167992, rs11553742, rs7576247 and rs3828329, were genotyped using TaqMan SNP genotyping assays. Common ACP1 alleles (i.e. ACP1*A, ACP1*B and ACP1*C) were determined by two of these SNPs. After the analysis, no evidence of association of the ACP1 genetic variants was found with CD or UC. Therefore, our results suggest that the ACP1 gene may not play a relevant role in the development of IBD.

Independent replication of an association of CNVR7113.6 with Crohn's disease in Caucasians

BACKGROUND

A recent genome-wide association study (GWAS) of copy number variants (CNVs) in Crohn's disease (CD) confirmed association of three CNVs. The GWAS also provided evidence that a fourth CNV, CNVR7113.6, on chromosome 17 may alter susceptibility to CD (P = 0.0018). The aim of our study was to confirm the CNVR7113.6 association by genotyping two independent inflammatory bowel disease (IBD) cohorts and by conducting a subsequent meta-analysis.

METHODS

In all, 1369 New Zealand Caucasians (489 CD patients, 463 ulcerative colitis [UC] patients, and 417 controls) and 2737 Spanish Caucasians (711 CD patients, 549 UC patients, and 1477 controls) were genotyped for a single nucleotide polymorphism (SNP), rs413778, in high linkage disequilibrium (r(2) = >0.99) with CNVR7113.6. Chi-square analysis was conducted to test for association of rs413778 with overall CD, UC, IBD, and with disease phenotype. New Zealand and Spanish genotypes were then combined with imputed rs413778 genotypes from the Wellcome Trust Case Control Consortium (WTCCC) and the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) CD datasets to conduct a meta-analysis.

RESULTS

The minor allele of rs413778 conferred protection against CD in the Spanish cohort (CD: P = 0.004, odds ratio [OR] = 0.82, 95% confidence interval [CI]: 0.71-0.94). A similar, albeit nonsignificant protective effect was observed in New Zealand CD patients (P = 0.098, OR = 0.83, 95% CI: 0.66-1.04). No association with UC or disease phenotypes was detected in either cohort. Meta-analysis found significant cumulative evidence for a protective effect of rs413778 in Caucasian CD (P = 1.19E-05, OR = 0.86, 95% CI: 0.80-0.92).

CONCLUSIONS

This study provides the first independent replication of the association of CNVR7113.6 with CD.

Differential association of two PTPN22 coding variants with Crohn's disease and ulcerative colitis

BACKGROUND

The PTPN22 gene is an important risk factor for human autoimmunity. The aim of this study was to evaluate for the first time the role of the R263Q PTPN22 polymorphism in ulcerative colitis (UC) and Crohn's disease (CD), and to reevaluate the association of the R620W PTPN22 polymorphism with both diseases.

METHODS

A total of 1677 UC patients, 1903 CD patients, and 3111 healthy controls from an initial case-control set of Spanish Caucasian ancestry and two independent sample sets of European ancestry (Dutch and New Zealand) were included in the study. Genotyping was performed using TaqMan SNP assays for the R263Q (rs33996649) and R620W (rs2476601) PTPN22 polymorphisms. Meta-analysis was performed on 6977 CD patients, 5695 UC patients, and 9254 controls to test the overall effect of the minor allele of R620W and R263Q polymorphisms.

RESULTS

The PTPN22 263Q loss-of-function variant showed initial evidence of association with UC in the Spanish cohort (P = 0.026, odds ratio [OR] = 0.61, 95% confidence interval [CI]: 0.39-0.95), which was confirmed in the meta-analysis (P = 0.013 pooled, OR = 0.69, 95% CI: 0.51-0.93). In contrast, the 263Q allele showed no association with CD (P = 0.22 pooled, OR = 1.16, 95% CI: 0.91-1.47). We found in the pooled analysis that the PTPN22 620W gain-of-function variant was associated with reduced risk of CD (P = 7.4E-06 pooled OR = 0.81, 95% CI: 0.75-0.89) but not of UC (P = 0.88 pooled, OR = 0.98, 95% CI: 0.85-1.15).

CONCLUSIONS

Our data suggest that two autoimmunity-associated polymorphisms of the PTPN22 gene are differentially associated with CD and UC. The R263Q polymorphism only associated with UC, whereas the R620W was significantly associated with only CD.

Analysis of the influence of two CD24 genetic variants in Crohn's disease and ulcerative colitis

The aim of this study was to evaluate the possible implication of CD24 gene in the genetic predisposition to inflammatory bowel disease (IBD). Our study population consisted of 1321 female Spanish individuals (369 Crohn's disease [CD] patients, 323 ulcerative colitis [UC] patients, and 629 healthy matched controls). Two putative functional polymorphisms, a C to T coding polymorphism (rs8734) and a TG deletion in the 3' untranslated region (rs3838646), were used as CD24 genetic markers and genotyped using a Taqman 5' allelic discrimination assay. The "del" allele of the dinucleotide deletion was associated with an increased risk of CD (odds ratio = 1.61, 95% confidence interval = 1.17-2.21, p(FDR) = 6.4E-03) but not with UC. Moreover, this allele was significant associated with the age of CD diagnosis between 17 and 40 years, the ileocolonic location, and the inflammatory behavior of CD. We observed no significant differences between the allelic or genotypic frequencies of the A57V polymorphism in our studied IBD cohort. Our results suggest that the rs3838646 CD24 polymorphism is part of the genetic background of CD.

CD40: novel association with Crohn's disease and replication in multiple sclerosis susceptibility

BACKGROUND

A functional polymorphism located at -1 from the start codon of the CD40 gene, rs1883832, was previously reported to disrupt a Kozak sequence essential for translation. It has been consistently associated with Graves' disease risk in populations of different ethnicity and genetic proxies of this variant evaluated in genome-wide association studies have shown evidence of an effect in rheumatoid arthritis and multiple sclerosis (MS) susceptibility. However, the protective allele associated with Graves' disease or rheumatoid arthritis has shown a risk role in MS, an effect that we aimed to replicate in the present work. We hypothesized that this functional polymorphism might also show an association with other complex autoimmune condition such as inflammatory bowel disease, given the CD40 overexpression previously observed in Crohn's disease (CD) lesions.

METHODOLOGY

Genotyping of rs1883832C>T was performed in 1564 MS, 1102 CD and 969 ulcerative colitis (UC) Spanish patients and in 2948 ethnically matched controls by TaqMan chemistry.

PRINCIPAL FINDINGS

The observed effect of the minor allele rs1883832T was replicated in our independent Spanish MS cohort [p = 0.025; OR (95% CI) = 1.12 (1.01-1.23)]. The frequency of the minor allele was also significantly higher in CD patients than in controls [p = 0.002; OR (95% CI) = 1.19 (1.06-1.33)]. This increased predisposition was not detected in UC patients [p = 0.5; OR (95% CI) = 1.04 (0.93-1.17)].

CONCLUSION

The impact of CD40 rs1883832 on MS and CD risk points to a common signaling shared by these autoimmune conditions.