Genome-wide association studies (GWASs) and follow-up studies of the most promising GWAS hits by the NIDDK Inflammatory Bowel Disease Genetics Consortium (IBDGC) and other members of the International IBDGC (IIBDGC) have been highly successful, as judged by the number of regions (>150) with genome-wide significant association signals in Crohn's disease (CD), ulcerative colitis (UC), or both forms of IBD;and their illumination of the probable involvement of specific biological pathways such as the IL-23/T helper 17 (Th17) immune pathway, autophagy, and mucosal barrier function in IBD pathogenesis. However, few of the genetic variants with the strongest association signals are predicted to change amino acid sequence or have other effects on protein structure. Most are in intronic or intergenic regions where they do not have immediately obvious functional effects. Together, they explain a modest proportion of the estimated heritability of CD and UC. Since effect sizes of individual risk-associated alleles are generally small, disease susceptibility probably arises from an accumulation of multiple small effects on biological pathways. Additional genetic studies that aim to fill in gaps in our understanding of the heritability should be complemented with the application of new statistical and computational methods to identify the strongest candidate IBD-causal variants in a gene network context. Coordinated investigation of the effects of candidate risk alleles on specific biological pathways in relevant tissues and cell types by NIDDK IBDGC Genetic Research Centers (GRCs) and other groups conducting ancillary studies is an essential strategy to dissect disease pathogenesis. IBD GWAS hits in multiple IL-23/Th17 immune pathway genes;GWAS hits that also implicate IL-23 signaling in ankylosing spondylitis, Behcet's disease, leprosy, and psoriasis;and a strong IL-23/Th17 immune pathway research environment at the University of Pittsburgh prompted us to begin exploration of the role of IBD-associated genetic variants in Th17 biology.
Our Specific Aims are:
Aim 1. Maintain an infrastructure for recruitment of study subjects, phenotyping, and biosample collection for NIDDK IBDGC Steering Committee-approved consortium-wide, GRC-specific, and ancillary studies;
Aim 2. Participate in the design and execution of NIDDK IBDGC and IIBDGC genetic studies that aim to identify the strongest candidate IBD-causal variants;
Aim 3. Examine the relationship between IBD-associated genetic variants and differential gene expression traits induced in activated effector memory T cells by inflammatory mediators (IL-23, IL-1?, and PGE2) known to be overexpressed in inflamed IBD tissues, to modulate Th17 function, and to be related to IBD-associated genes.

Public Health Relevance

Inflammatory bowel disease (IBD) has both genetic and non-genetic risk factors. Genetic variation that has been associated with this complex disorder so far explains only a modest proportion of the estimated disease heritability, so additional genetic studies are needed to more fully explain the heritability. To learn how IBD arises and progresses, we must also understand how the genetic variation associated with IBD affects human biology. We propose to continue supporting the NIDDK IBD Genetics Consortium in all its activities and to explore the effect of genetic variants associated with IBD on immune biology.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project--Cooperative Agreements (U01)
Project #
5U01DK062420-13
Application #
8733653
Study Section
Special Emphasis Panel (ZDK1-GRB-G (O3))
Program Officer
Karp, Robert W
Project Start
2002-09-30
Project End
2017-08-31
Budget Start
2014-09-01
Budget End
2015-08-31
Support Year
13
Fiscal Year
2014
Total Cost
$368,703
Indirect Cost
$124,825
Name
University of Pittsburgh
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
004514360
City
Pittsburgh
State
PA
Country
United States
Zip Code
15213
Wang, Ming-Hsi; Fiocchi, Claudio; Zhu, Xiaofeng et al. (2014) Gene-gene and gene-environment interactions in ulcerative colitis. Hum Genet 133:547-58
Weizman, Adam; Huang, Brian; Berel, Dror et al. (2014) Clinical, serologic, and genetic factors associated with pyoderma gangrenosum and erythema nodosum in inflammatory bowel disease patients. Inflamm Bowel Dis 20:525-33
Wang, Ming-Hsi; Fiocchi, Claudio; Ripke, Stephan et al. (2013) A novel approach to detect cumulative genetic effects and genetic interactions in Crohn's disease. Inflamm Bowel Dis 19:1799-808
Adamik, Juraj; Henkel, Matthew; Ray, Anuradha et al. (2013) The IL17A and IL17F loci have divergent histone modifications and are differentially regulated by prostaglandin E2 in Th17 cells. Cytokine 64:404-12
Lazarev, Mark; Huang, Chengrui; Bitton, Alain et al. (2013) Relationship between proximal Crohn's disease location and disease behavior and surgery: a cross-sectional study of the IBD Genetics Consortium. Am J Gastroenterol 108:106-12
Beaudoin, Mélissa; Goyette, Philippe; Boucher, Gabrielle et al. (2013) Deep resequencing of GWAS loci identifies rare variants in CARD9, IL23R and RNF186 that are associated with ulcerative colitis. PLoS Genet 9:e1003723
Achkar, J-P; Klei, L; de Bakker, P I W et al. (2012) Amino acid position 11 of HLA-DRýý1 is a major determinant of chromosome 6p association with ulcerative colitis. Genes Immun 13:245-52
Rivas, Manuel A; Beaudoin, Melissa; Gardet, Agnes et al. (2011) Deep resequencing of GWAS loci identifies independent rare variants associated with inflammatory bowel disease. Nat Genet 43:1066-73
Muise, Aleixo M; Walters, Thomas; Xu, Wei et al. (2011) Single nucleotide polymorphisms that increase expression of the guanosine triphosphatase RAC1 are associated with ulcerative colitis. Gastroenterology 141:633-41
Anderson, Carl A; Boucher, Gabrielle; Lees, Charlie W et al. (2011) Meta-analysis identifies 29 additional ulcerative colitis risk loci, increasing the number of confirmed associations to 47. Nat Genet 43:246-52

Showing the most recent 10 out of 28 publications