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Expression analysis in intestinal mucosa reveals complex relations among genes under the association peaks in celiac disease.

ABSTRACT: Celiac disease is a chronic immune-mediated disorder with an important genetic component. To date, there are 57 independent association signals from 39 non-HLA loci, and a total of 66 candidate genes have been proposed. We aimed to scrutinize the functional implication of 45 of those genes by analyzing their expression in the disease tissue of celiac patients (at diagnosis/treatment) compared with non-celiac controls. Moreover, we investigated the SNP genotype effect in gene expression and performed coexpression analyses. Several genes showed differential expression among disease groups, most of them related to immune response. Multiple trans-eQTLs but only four cis-eQTLs were found, and surprisingly the genotype effect seems to be stimulus dependent as it differs among groups. Coexpression levels vary from higher to lower levels in active patients at diagnosis, treated patients and non-celiac controls respectively. A subset of 18 genes tightly correlated in both groups of patients but not in controls was identified. Interestingly, this subset of genes was influenced by the genotype of three SNPs. One of the SNPs, rs1018326 on chromosome two is on top of a known lincRNA whose function is not yet described, and whose expression seems to be upregulated in active disease when comparing biopsy pairs from the same individuals. Our results strongly suggest that the effects of disease-associated SNPs go far beyond the oversimplistic idea of transcriptional control at a nearby locus. Further investigations are needed to determine how each variant disrupts fine-tuning mechanisms in the genome that eventually lead to disease.

SUBMITTER: Plaza-Izurieta L

PROVIDER: S-EPMC4795102 | biostudies-literature | 2015 Aug

REPOSITORIES: biostudies-literature

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Expression analysis in intestinal mucosa reveals complex relations among genes under the association peaks in celiac disease.

Plaza-Izurieta Leticia L Fernandez-Jimenez Nora N Irastorza Iñaki I Jauregi-Miguel Amaia A Romero-Garmendia Irati I Vitoria Juan Carlos JC Bilbao Jose Ramon JR

European journal of human genetics : EJHG 20141112 8

Celiac disease is a chronic immune-mediated disorder with an important genetic component. To date, there are 57 independent association signals from 39 non-HLA loci, and a total of 66 candidate genes have been proposed. We aimed to scrutinize the functional implication of 45 of those genes by analyzing their expression in the disease tissue of celiac patients (at diagnosis/treatment) compared with non-celiac controls. Moreover, we investigated the SNP genotype effect in gene expression and perfo ...[more]

PMID: 25388004

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Project description:Background & Aims: Traditional celiac disease diagnostics based on histomorphometric evaluations are liable to misinterpretations due to the common technical flaws e.g. wrong orientation of the biopsy and subjective errors are relatively common e.g. interobserver errors. We envisioned that there is a need for molecular histomorphometric tool that obviates these error sources yielding an objective ratio instead. Gene expression determine the state of a tissue, so the changes in expression may be associated with the severity of lesions during CD and can be used to classify it. Methods: 15 CD patients, who have been at least one year on gluten-free diet, were enrolled. All participants were biopsied before and after the gluten challenge (10 weeks, 4 grams of gluten daily). 6 healthy non-CD individuals were included as controls. Biopsies were taken on PAXgene biological fixative and embedded in paraffin and Vh/Cd ratio was assessed. RNA was extracted from the same sections and subjected to genome-wide 3’RNA-sequencing. Sequencing data was used to determine differentially expressed genes and regression model, that successfully describes the mucosal damage, was created and tested in independent material. Results: 167 differentially expressed genes were identified in healthy vs. treated CD comparisons with 117 genes downregulated and 50 genes upregulated. 415 differentially expressed genes were identified in Post gluten challenge to Treated CD comparisons with 195 genes downregulated and 220 genes upregulated. 119 genes whose expression highly correlates to Vh/Cd ratio (Spearman’s rank correlation coefficient, |rho|>0.7) were identified. Gene ontology analyses show that genes involved in cellular response to cytokines, including interferons, were over-represented. Stepwise regression allowed us computationally cut down the number of genes, that describe Vh/Cd ratio changes, to 7 and IELs number to 5. Created models describe 98.9% of observed Vh/Cd and 97.5% of IELs number variabilities; there is a strong correlation between the model’s predicted and observed ratios. Conclusions: Adoption of molecular histomorphometry, with our selected set of target genes, is quantitative and reliable way of estimating gluten-induced mucosal injury and inflammation. By including this technology one can overcome the typical shortcomings common in celiac disease diagnostics based on traditional histomorphometry analyses alone. Likewise, molecular histomorphometry is a promising instrument when incorporated in clinical trials where assessing drug efficacy on mucosal health is paramount. In addition, despite deemed healthy, based on traditional histomorphometric analyses, celiac patients on gluten free diet have significantly distinctive molecular histomorphometric pattern when compared to healthy controls.

Dataset Information

Expression analysis in intestinal mucosa reveals complex relations among genes under the association peaks in celiac disease.

Publications

Expression analysis in intestinal mucosa reveals complex relations among genes under the association peaks in celiac disease.

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