Dataset Information

Independent and population-specific association of risk variants at the IRGM locus with Crohn's disease.

ABSTRACT: DNA polymorphisms in a region on chromosome 5q33.1 which contains two genes, immunity related GTPase related family, M (IRGM) and zinc finger protein 300 (ZNF300), are associated with Crohn's disease (CD). The deleted allele of a 20 kb copy number variation (CNV) upstream of IRGM was recently shown to be in strong linkage disequilibrium (LD) with the CD-associated single nucleotide polymorphisms and is itself associated with CD (P < 0.01). The deletion was correlated with increased or reduced expression of IRGM in transformed cells in a cell line-dependent manner, and has been proposed as a likely causal variant. We report here that small insertion/deletion polymorphisms in the promoter and 5' untranslated region of IRGM are, together with the CNV, strongly associated with CD (P = 1.37 x 10(-5) to 1.40 x 10(-9)), and that the CNV and the 5'-untranslated region variant -308(GTTT)(5) contribute independently to CD susceptibility (P = 2.6 x 10(-7) and P = 2 x 10(-5), respectively). We also show that the CD risk haplotype is associated with a significant decrease in IRGM expression (P < 10(-12)) in untransformed lymphocytes from CD patients. Further analysis of these variants in a Japanese CD case-control sample and of IRGM expression in HapMap populations revealed that neither the IRGM insertion/deletion polymorphisms nor the CNV was associated with CD or with altered IRGM expression in the Asian population. This suggests that the involvement of the IRGM risk haplotype in the pathogenesis of CD requires gene-gene or gene-environment interactions which are absent in Asian populations, or that none of the variants analysed are causal, and that the true causal variants arose after the European-Asian split.

SUBMITTER: Prescott NJ

PROVIDER: S-EPMC2850616 | biostudies-literature | 2010 May

REPOSITORIES: biostudies-literature

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Independent and population-specific association of risk variants at the IRGM locus with Crohn's disease.

Prescott Natalie J NJ Dominy Katherine M KM Kubo Michiaki M Lewis Cathryn M CM Fisher Sheila A SA Redon Richard R Huang Ni N Stranger Barbara E BE Blaszczyk Katarzyna K Hudspith Barry B Parkes Gareth G Hosono Naoya N Yamazaki Keiko K Onnie Clive M CM Forbes Alastair A Dermitzakis Emmanouil T ET Nakamura Yusuke Y Mansfield John C JC Sanderson Jeremy J Hurles Matthew E ME Roberts Roland G RG Mathew Christopher G CG

Human molecular genetics 20100127 9

DNA polymorphisms in a region on chromosome 5q33.1 which contains two genes, immunity related GTPase related family, M (IRGM) and zinc finger protein 300 (ZNF300), are associated with Crohn's disease (CD). The deleted allele of a 20 kb copy number variation (CNV) upstream of IRGM was recently shown to be in strong linkage disequilibrium (LD) with the CD-associated single nucleotide polymorphisms and is itself associated with CD (P < 0.01). The deletion was correlated with increased or reduced ex ...[more]

PMID: 20106866

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Project description:Crohn's disease (CD) is a chronic inflammatory gastrointestinal disorder. Genetic association studies have implicated dysregulated autophagy in CD. Among risk loci identified are a promoter single nucleotide polymorphism (SNP)( rs13361189 ) and two intragenic SNPs ( rs9637876 , rs10065172 ) in immunity-related GTPase family M ( IRGM) a gene that encodes a protein of the autophagy initiation complex. All three SNPs have been proposed to modify IRGM expression, but reports have been divergent and largely derived from cell lines. Here, analyzing RNA-Sequencing data of human tissues from the Genotype-Tissue Expression Project, we found that rs13361189 minor allele carriers had reduced IRGM expression in whole blood and terminal ileum, and upregulation in ileum of ZNF300P1, a locus adjacent to IRGM on chromosome 5q33.1 that encodes a long noncoding RNA. Whole blood and ileum from minor allele carriers had altered expression of multiple additional genes that have previously been linked to colitis and/or autophagy. Notable among these was an increase in ileum of LTF (lactoferrin), an established fecal inflammatory biomarker of CD, and in whole blood of TNF, a key cytokine in CD pathogenesis. Last, we confirmed that risk alleles at all three loci associated with increased risk for CD but not ulcerative colitis in a case-control study. Taken together, our findings suggest that genetically encoded IRGM deficiency may predispose to CD through dysregulation of inflammatory gene networks. Gene expression profiling of disease target tissues in genetically susceptible populations is a promising strategy for revealing new leads for the study of molecular pathogenesis and, potentially, for precision medicine. NEW & NOTEWORTHY Single nucleotide polymorphisms in immunity-related GTPase family M ( IRGM), a gene that encodes an autophagy initiation protein, have been linked epidemiologically to increased risk for Crohn's disease (CD). Here, we show for the first time that subjects with risk alleles at two such loci, rs13361189 and rs10065172 , have reduced IRGM expression in whole blood and terminal ileum, as well as dysregulated expression of a wide array of additional genes that regulate inflammation and autophagy.

Project description:The aim of the present meta-analysis was to evaluate the correlation between a common polymorphism, rs13361189 C>T in the immunity-related GTPase M (IRGM) gene, and susceptibility to Crohn's disease (CD). The PubMed, CISCOM, CINAHL, Web of Science, Google Scholar, EBSCO, Cochrane Library and CBM databases were investigated from database inception through to October 1, 2013 without the application of any language restrictions. The meta-analysis was performed using STATA 12.0 software and the relative risk (RR) with a 95% confidence interval (CI) was calculated. Seven case-control studies were included with a total of 3,093 CD patients and 3,227 healthy control subjects. The results of the meta-analysis revealed that the IRGM rs13361189 polymorphism correlates with an increased risk of CD (T allele versus C allele: RR=1.25 with 95% CI, 1.04-1.50; P=0.016 and CT + TT versus CC: RR=1.21 with 95% CI, 1.03-1.42; P=0.018). A subgroup analysis conducted using a genotyping method indicated that the IRGM rs13361189 polymorphism was correlated with an increased risk of CD in the TaqMan® (T allele versus C allele: RR=1.32 with 95% CI, 1.01-1.73; P=0.042) and the polymerase chain reaction-restriction fragment length polymorphism subgroups (T allele versus C allele: RR=1.80 with 95% CI, 1.32-2.45; P<0.001 and CT + TT versus CC: RR=1.61 with 95% CI, 1.19-2.18; P=0.018). However, no correlation was observed in the direct sequencing subgroup (P>0.05). Further subgroup analysis by sample size demonstrated significant correlations between the IRGM rs13361189 polymorphism and an increased risk of CD in the large sample-size subgroup (T allele versus C allele: RR=1.46 with 95% CI, 1.26-1.68; P<0.001 and CT + TT versus CC: RR=1.40 with 95% CI, 1.21-1.62; P<0.001). However, no correlation was identified between the IRGM rs13361189 polymorphism and CD risk in the small sample-size subgroup (P>0.05). The present meta-analysis indicated that the IRGM rs13361189 polymorphism may contribute to susceptibility to CD. Thus, IRGM rs13361189 polymorphism may be a potential biomarker for the early diagnosis of CD.

Dataset Information

Independent and population-specific association of risk variants at the IRGM locus with Crohn's disease.

Publications

Independent and population-specific association of risk variants at the IRGM locus with Crohn's disease.

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