EQTL in diseased colon tissue identifies novel target genes associated with IBD
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ABSTRACT: Genome-wide association studies (GWAS) have identified over 300 loci associated with the inflammatory bowel diseases (IBD), but putative causal genes for most are unknown. We conducted the largest disease-focused expression quantitative trait loci (eQTL) analysis using colon tissue from 252 IBD patients to determine genetic effects on gene expression and potential contribution to IBD. Combined with two non-IBD colon eQTL studies, we identified 194 potential target genes for 108 GWAS loci. eQTL in IBD tissue were enriched for IBD GWAS loci colocalizations, provided novel evidence for IBD-associated genes such as ABO and TNFRSF14, and identified additional target genes compared to non-IBD tissue eQTL. IBD-associated eQTL unique to diseased tissue had distinct regulatory and functional characteristics with increased effect sizes. Together, these highlight the importance of eQTL studies in diseased tissue for understanding functional consequences of genetic variants, and elucidating molecular mechanisms and regulation of key genes involved in IBD.
Project description:Genome wide association studies (GWAS) have identified single nucleotide polymorphisms (SNPs) associated with diseases of the colon including inflammatory bowel diseases (IBD) and colorectal cancer (CRC). However, the functional role of many of these SNPs is largely unknown and tissue-specific resources are lacking. Expression quantitative trait loci (eQTL) mapping identifies target genes of disease-associated SNPs. Here, we comprehensively map eQTLs in the human colon, assess their relevance for GWAS of colonic diseases and provide functional characterization.
Project description:Genome wide association studies (GWAS) have identified single nucleotide polymorphisms (SNPs) associated with diseases of the colon including inflammatory bowel diseases (IBD) and colorectal cancer (CRC). However, the functional role of many of these SNPs is largely unknown and tissue-specific resources are lacking. Expression quantitative trait loci (eQTL) mapping identifies target genes of disease-associated SNPs. Here, we comprehensively map eQTLs in the human colon, assess their relevance for GWAS of colonic diseases and provide functional characterization. Subjects included 40 healthy African American individuals who had undergone colonoscopy at the University of Illinois Chicago for screening purposes. Distal colonic biopsies were obtained in all subjects at 20 cm from the anal verge at the recto-sigmoid junction and were immediately dispensed in RNAlater. Total mRNA was extracted from manually ground tissue with the Promega Maxwell 16 Tissue LEV Total RNA Purification Kit for automated purification on the Maxwell 16 Instrument and mRNA analysis was performed on Illumina HumanHT-12v4 Expression BeadChip arrays. Genomic DNA was obtained from whole-blood samples from the same individuals and genotyped using the Affymetrix Axiom Genome-wide Pan-African array. Cis- and trans-eQTL analyses were performed on the dataset of 8.4 million imputed SNPs and 16,252 expression probes corresponding to 12,363 unique autosomal genes in 40 subjects. Associations between SNPs and gene expression levels were examined with Matrix eQTL using linear regression. False discovery rate calculations were performed separately for cis- and trans-eQTLs.
Project description:Genome-wide association studies (GWAS) have identified 19 risk variants associated with colorectal cancer. As most of these risk variants reside outside the coding regions of genes, we conducted cis-expression quantitative trait loci (cis-eQTL) analyses to investigate possible regulatory functions on the expression of neighboring genes. Forty microsatellite stable and CpG island methylator phenotype-negative colorectal tumors and paired adjacent-normal colon tissues were used for genome-wide SNP and gene expression profiling in our cis-eQTL analyses. This submission represents transcriptome component of study.
Project description:We performed RNA sequencing to produce expression quantitative trait loci (eQTL) database of Crohn's disease patients. Using this eQTL data, we tried to determine the most functionally relevant genes at the established Crohn’s disease loci identified in genome-wide association studies (GWAS) involving Asian populations and to find novel disease-associated genes.
Project description:With a greater understanding of the genetic risk variants associated with inflammatory bowel disease, there is a need to prioritize candidate genes within risk loci leading to the disease-SNP association. We created a custom NanoString probeset to capture 678 genes of interest in IBD (including 440 genes encoded within IBD risk loci and 15 housekeeping genes) - 22% of genes were not captured on traditional microarray platforms. Total RNA extracted from terminal ileum and colon tissues (uninflamed and inflamed) was used from patients with Crohn's disease and ulcerative colitis and healthy controls. We studied differential expression and performed an eQTL analysis to prioritize candidate genes within the risk loci.
Project description:In recent years genome-wide association studies (GWAS) have uncovered numerous chromosomal loci associated with various electrocardiographic traits and cardiac arrhythmia predisposition. A considerable fraction of these loci lie within inter-genic regions. Trait-associated SNPs located in putative regulatory regions likely exert their effect by modulating gene expression. Hence, the key to unraveling the molecular mechanisms underlying cardiac traits is to interrogate variants for association with differential transcript abundance by expression quantitative trait locus (eQTL) analysis. In this study we conducted an eQTL analysis of human heart. To this end, left ventricular mycardium samples from non-diseased human donor hearts were hybridized to Illumina HumanOmniExpress BeadChips for genotyping (n = 129) and Illumina Human HT12 Version 4 BeadChips (n = 129) for transcription profiling. To assess the genotypes of 129 human donor hearts from the study, genome-wide SNP genotyping was carried out using Illumina HumanOmniExpress Beadchips interrogating 733,202 genetic markers.
Project description:Genome-wide association studies (GWAS) have been pivotal to increasing our understanding of intestinal disease. However, the mode by which genetic variation results in phenotypic change remains largely unknown, with many associated polymorphisms likely to modulate gene expression. Analyses of expression quantitative trait loci (eQTL) to date indicate that as many as 50% of these are tissue specific. Here we report a comprehensive eQTL scan of intestinal tissue.
Project description:Genome-wide association studies (GWAS) have been pivotal to increasing our understanding of intestinal disease. However, the mode by which genetic variation results in phenotypic change remains largely unknown, with many associated polymorphisms likely to modulate gene expression. Analyses of expression quantitative trait loci (eQTL) to date indicate that as many as 50% of these are tissue specific. Here we report a comprehensive eQTL scan of intestinal tissue.
Project description:In recent years genome-wide association studies (GWAS) have uncovered numerous chromosomal loci associated with various electrocardiographic traits and cardiac arrhythmia predisposition. A considerable fraction of these loci lie within inter-genic regions. Trait-associated SNPs located in putative regulatory regions likely exert their effect by modulating gene expression. Hence, the key to unraveling the molecular mechanisms underlying cardiac traits is to interrogate variants for association with differential transcript abundance by expression quantitative trait locus (eQTL) analysis. In this study we conducted an eQTL analysis of human heart. To this end, left ventricular mycardium samples from non-diseased human donor hearts were hybridized to Illumina HumanOmniExpress BeadChips for genotyping (n = 129) and Illumina Human HT12 Version 4 BeadChips (n = 129) for transcription profiling. To assess the gene expression levels of 129 human donor hearts from the study, genome-wide transcription profiling was carried out using Illumina Human HT12 Version 4 Beadchips interrogating over 47,000 unique transcripts (total of 47323 probes including controls).