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Genetics of Inflammatory Bowel Diseases.

ABSTRACT: In this review, we provide an update on genome-wide association studies (GWAS) in inflammatory bowel disease (IBD). In addition, we summarize progress in defining the functional consequences of associated alleles for coding and noncoding genetic variation. In the small minority of loci where major association signals correspond to nonsynonymous variation, we summarize studies defining their functional effects and implications for therapeutic targeting. Importantly, the large majority of GWAS-associated loci involve noncoding variation, many of which modulate levels of gene expression. Recent expression quantitative trait loci (eQTL) studies have established that the expression of most human genes is regulated by noncoding genetic variations. Significant advances in defining the epigenetic landscape have demonstrated that IBD GWAS signals are highly enriched within cell-specific active enhancer marks. Studies in European ancestry populations have dominated the landscape of IBD genetics studies, but increasingly, studies in Asian and African-American populations are being reported. Common variation accounts for only a modest fraction of the predicted heritability and the role of rare genetic variation of higher effects (ie, odds ratios markedly deviating from 1) is increasingly being identified through sequencing efforts. These sequencing studies have been particularly productive in more severe very early onset cases. A major challenge in IBD genetics will be harnessing the vast array of genetic discovery for clinical utility through emerging precision medical initiatives. In this article, we discuss the rapidly evolving area of direct-to-consumer genetic testing and the current utility of clinical exome sequencing, especially in very early onset, severe IBD cases. We summarize recent progress in the pharmacogenetics of IBD with respect to partitioning patient responses to anti-TNF and thiopurine therapies. Highly collaborative studies across research centers and across subspecialties and disciplines will be required to fully realize the promise of genetic discovery in IBD.

SUBMITTER: McGovern DP

PROVIDER: S-EPMC4915781 | biostudies-literature | 2015 Oct

REPOSITORIES: biostudies-literature

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Genetics of Inflammatory Bowel Diseases.

McGovern Dermot P B DP Kugathasan Subra S Cho Judy H JH

Gastroenterology 20150807 5

In this review, we provide an update on genome-wide association studies (GWAS) in inflammatory bowel disease (IBD). In addition, we summarize progress in defining the functional consequences of associated alleles for coding and noncoding genetic variation. In the small minority of loci where major association signals correspond to nonsynonymous variation, we summarize studies defining their functional effects and implications for therapeutic targeting. Importantly, the large majority of GWAS-ass ...[more]

PMID: 26255561

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Project description:Alexithymia is usually described by three main dimensions difficulty identifying feelings (DIF), difficulty describing feelings (DDF), and externally oriented thinking (EOT). The most commonly used questionnaire investigating alexithymia, the Toronto Alexithymia Scale (TAS-20), supports this three-factor structure. One important assumption is that alexithymia severity is associated to vulnerability to somatic diseases, among them gastrointestinal disorders. However, the association between alexithymia and gastrointestinal disorders is not systematic, thus questioning the role of alexithymia as a vulnerability factor for those illnesses. A recent factor analysis suggested another four-factor structure for the TAS-20: difficulties in awareness of feelings (DAF), difficulties in interoceptive abilities (DIA), externally oriented thinking (EOT), and poor affective sharing (PAS). We assume that DIA and DAF might be more relevant to investigate the association between alexithymia and gastrointestinal disorders. The rationale is that DIA and DAF reflect impairments in emotion regulation that could contribute to an inappropriate autonomic and HPA axis homeostasis in irritable bowel syndrome (IBS), ulcerative colitis (UC), or Crohn's disease (CD). The aim of this study was to investigate whether DIA and DAF are associated with the presence of IBS, UC or CD, while checking for anxiety, depression, parasympathetic (vagus nerve) activity and cortisol levels. We recruited control participants (n=26), and patients in remission who were diagnosed with IBS (n=24), UC (n=18), or CD (n=21). Participants completed questionnaires to assess anxiety, depression, and alexithymia. A blood sample and an electrocardiogram were used to measure the level of cortisol and parasympathetic activity, respectively. Logistic regressions with the four-factor structure of the TAS-20 revealed that DIA was a significant predictor of IBS (W(1)=6.27, p=.01). Conversely, DIA and DAF were not significant predictors in CD and UC patients. However, low cortisol level was a significant predictor of UC (W(1)=4.67, p=.035). Additional logistic regressions based on the original 3-factor structure of TAS-20 (DIF, DDF, and EOT) showed that only DDF was a significant predictor of CD [W(1)=6.16, p < .001]. The present study suggests that DIA is an important dimension for assessing potential risk for gastrointestinal diseases, in particular for IBS.

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Genetics of Inflammatory Bowel Diseases.

Publications

Genetics of Inflammatory Bowel Diseases.

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