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Elevation in cell cycle and protein metabolism gene transcription in inactive colonic tissue from Icelandic patients with ulcerative colitis

ABSTRACT: BACKGROUND & AIMS: Ulcerative colitis (UC) is a chronic relapsing inflammatory disorder that affects the colonic epithelium. A combination of genetic and environmental factors is thought to be involved in the pathogenesis, resulting in an abnormal immune response and destruction of the colonic epithelium. In Iceland, the incidence of UC is one of the highest in the world and is three times more common than Crohn’s disease. Previous studies have suggested a genetic component may have an influence on the increased incidence. The aim of this study was to characterise a cohort of patients with UC and identify potential germ line mutations and pathways which could be associated with UC in this population. METHODS: We performed exome sequencing of genomic DNA and genome-wide microarray analysis on macroscopically non-inflamed colonic mucosa from Icelandic patients with UC and age and sexed matched controls. Gene-ontology analysis was used to identify common processes and pathways differentially expressed in tissue from UC cases. Exome sequence data were examined for very rare or novel mutations which might be over represented in the UC cohort. Combined matching of variant analysis and downstream influence on transcriptomic expression in the rectum was also analysed. RESULTS: Non-inflamed colonic tissue from patients with UC demonstrated a significant alteration in the transcriptomic profile compared to controls. Over 2,000 genes were differentially expressed in rectal tissue from UC patients and gene ontology analysis identified an up-regulation in genes associated with cell cycle control and protein processing in the endoplasmic reticulum. Exome sequencing identified two missense mutations in thiopurine S-methyltransferase (TPMT) with a minor allele frequency of 0.22 in the UC patients compared to a reported 0.062 in the Icelandic population and 0.03 in the non-Finnish European populations. A predicted damaging mutation in the inflammatory bowel disease associated gene SLC26A3 was identified which was associated with increased expression of DUOX2 and DUOXA2 in UC rectal tissue. CONCLUSIONS: In patients with UC, the colonic mucosa demonstrates a clear alteration in gene expression compared to control subjects. There is evidence of an elevation in genes involved with cell proliferation and the processing of proteins within the endoplasmic reticulum. Exome sequencing identified an increased prevalence of two damaging TPMT variants within the Icelandic UC population, which would suggest screening the UC population prior to initiation of therapy is warranted in order to avoid the serious toxicity associated with these mutations and azathioprine treatment.

ORGANISM(S): Homo sapiens

PROVIDER: GSE105074 | GEO | 2018/11/01

REPOSITORIES: GEO

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Project description:Inflammatory bowel disease (IBD) is a complex multi-factorial inflammatory disease with Crohn’s disease (CD) and ulcerative colitis (UC) being the two most common forms. A number of transcriptional profiling studies have provided compelling evidence that describe the role of protein-coding genes and microRNAs in modulating the immune responses in IBD. In the present study, we performed a genome-wide transcriptome profiling of lncRNAs and protein-coding genes in inflamed and non-inflamed colon pinch biopsies from the IBD patients using expression microarrays platform. In this study, we identified widespread dysregulation of lncRNAs and protein-coding genes in both inflamed and non-inflamed CD and UC compared to the healthy controls. In case of inflamed CD and UC (iCD and iUC), we identified 438 and 745 differentially expressed lncRNAs, respectively, while in case of the non-inflamed CD and UC (niCD and niUC), we identified 12 and 19 differentially expressed lncRNAs, respectively. We also observed significant enrichment (p-value < 0.001, Pearson’s Chi-squared test) for 96 differentially expressed lncRNAs and 154 protein-coding genes within the IBD susceptibility loci. Furthermore, we found strong positive expression correlations for the intersecting and cis-neighboring differentially expressed IBD loci-associated lncRNA-protein-coding gene pairs. The functional annotation analysis of differentially expressed genes revealed that they are involved in immune response, pro-inflammatory cytokine activity and MHC protein complex. The lncRNA expression profiling in both inflamed and non-inflamed CD and UC, successfully stratified IBD patients from the healthy controls. Taken together, the identified lncRNA transcriptional signature along with clinically relevant parameters suggests their potential as biomarkers in IBD. A total of 96 biopsy samples (including 6 samples used as technical replicates) extracted from different colonic locations from 45 patients (CD=13, UC=20, Controls=12) were profiled using Agilent Custom 8x60K format lncRNA expression microarray. In Gencode v15 lncRNA microarray design, each lncRNA transcript is targeted by two probes covering 22,001 lncRNA transcripts corresponding to 12,963 lncRNA genes. In addition, each array contains 17,535 randomly-selected protein-coding targets, of which 15,182 (unique 12,787) correspond to protein-coding genes.

Project description:Background and aims: Mucosal abnormalities are potentially important in the primary pathogenesis of ulcerative colitis (UC). We investigated the mucosal transcriptomic expression profiles of biopsies from patients with UC and healthy controls (HC), taken from macroscopically non-inflamed tissue from the terminal ileum and three colonic locations with the objective of identifying abnormal molecules that might be involved in disease development. Methods: Whole-genome transcriptional analysis was performed on intestinal biopsies taken from 24 UC, 26 HC and 14 patients with CrohnM-bM-^@M-^Ys disease. Differential gene expression analysis was performed at each tissue location separately and results were then meta-analysed using FisherM-bM-^@M-^Ys method. Significantly differentially expressed genes were validated using qPCR. Gene location within the colon was determined using immunohistochemistry, subcellular fractionation, electron and confocal microscopy. DNA methylation was quantified by pyrosequencing. Results: Seven probes were abnormally expressed throughout the colon in UC patients with Family with sequence similarity member 5 C (FAM5C) being the most significantly underexpressed. Attenuated expression of FAM5C in UC was independent of inflammation, unrelated to phenotype or treatment, and remained low at rebiopsy approximately 23 months later. FAM5C is localised to the brush border of the colonic epithelium and expression is influenced by DNA methylation within its promoter. Conclusion: Genome-wide expression analysis of non-inflamed mucosal biopsies from UC patients identified FAM5C as significantly under-expressed throughout the colon in a major sub-set of patients with UC. Low levels of this gene could predispose to or contribute to the maintenance of the characteristic mucosal inflammation seen in this condition. Total RNA was extracted from the intestinal biopsies taken from macroscopically normal mucosa in the rectum, descending colon, ascending colon and terminal ileum in clinically quiescent Ulcerative colitis and Crohn's disease patients and compared to healthy controls. Normalized data for 26,261 probes out of 47,323 only. Criteria for inclusion not specified. The non-normalized matrix contains the complete non-normalized data for all probes.

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Elevation in cell cycle and protein metabolism gene transcription in inactive colonic tissue from Icelandic patients with ulcerative colitis

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