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Genetic Susceptibility in IBD: Overlap Between Ulcerative Colitis and Crohn's Disease

Doecke, James D. BSc (Hons), PhD1,2,3; Simms, Lisa A. BSc (Hons)4; Zhao, Zhen Zhen BSc, PhD5; Huang, Ning BSc4; Hanigan, Katherine BSc4; Krishnaprasad, Krupa BE (Biotech)4,7; Roberts, Rebecca L. PhD8; Andrews, Jane M. MD, PhD, AGAF7; Mahy, Gillian FRCP, FRACP9; Bampton, Peter MD, FRACP, AGAF10; Lewindon, Peter MBBS, FRACP, PhD11,12; Florin, Timothy MBBS (Hons), MSc, FRACP12,13; Lawrance, Ian C. MBBS (Hons), PhD, FRACP14,15; Gearry, Richard B. MB, ChB, FRACP, PhD16; Montgomery, Grant W. BSc, PhD5; Radford-Smith, Graham L. MB, ChB, MRCP, FRACP, PhD4,6,12

doi: 10.1097/MIB.0b013e3182810041
Original Basic Science Articles

Background: The etiology of ulcerative colitis (UC) and Crohn's disease (CD) involves both genetic and environmental components. Multiple UC and CD susceptibility genes have been identified through genome-wide association studies and subsequent meta-analyses. These studies have also highlighted the presence of genes common to both diseases, and shared with several other autoimmune disorders. The aim of this study was to identify single nucleotide polymorphisms (SNPs) recently identified by the International IBD Genetics Consortium (IIBDGC) demonstrating that highly significant associations with CD could also confer genetic susceptibility to UC.

Methods: Statistical modeling was performed on 29 CD-associated SNPs. The study comprised of 1652 UC cases from the Australia and New Zealand IBD Consortium and 2363 Australian population-based controls.

Results: After adjustment for multiple comparisons, only one SNP, rs3024505, was significantly associated with UC (P = 0.001). Independent chi-square analyses identified odds ratios of 2.22 (1.48–3.37) for the rare homozygous genotype, and 1.20 (1.06–1.35) for the minor allele. Five other SNPs demonstrated moderate to weak associations with UC.

Conclusions: Of the 29 SNPs conferring high genetic susceptibility to CD, 28 were not associated with UC, thus indicating that for this SNP set there is a low level of overlap between the two major forms of IBD. Only one SNP, rs3024505 (Chr 1q32.1, upstream of IL10), was associated with susceptibility to UC. The identification of this SNP replicates a finding from Franke et al (2008), where the rs3024505 SNP was strongly associated with UC across multiple European populations.

Article first published online 23 January 2013

1The Australian E-Health Research Centre, Queensland, Australia

2CSIRO Preventative Health Flagship, Parkville, Victoria, Australia

3CSIRO Mathematics and Information Sciences, Macquarie University, Australia

4Inflammatory Bowel Diseases, Queensland Institute of Medical Research, Brisbane, Australia

5Molecular Epidemiology, Queensland Institute of Medical Research, Brisbane, Australia

6Department of Gastroenterology, Royal Brisbane and Women's Hospital, Brisbane, Australia

7IBD Service, Department of Gastroenterology & Hepatology, Royal Adelaide Hospital & School of Medicine, University of Adelaide, Adelaide, Australia

8Department of Biochemistry, University of Otago, Dunedin, New Zealand

9Department of Gastroenterology, The Townsville Hospital, Townsville, Australia

10Department of Gastroenterology & Hepatology, Flinders Medical Centre, Adelaide, Australia

11Department of Gastroenterology, Royal Children's Hospital, Herston, Brisbane, Australia

12Department of Medicine, University of Queensland, Australia

13Mater Health Services, Brisbane, Australia

14School of Medicine and Pharmacology, University of Western Australia, Perth, Australia

15Centre for inflammatory Bowel Diseases, Fremantle Hospital, Fremantle, Australia

16Dept of Gastroenterology, Christchurch Hospital, and Dept of Medicine, University of Otago, Christchurch, New Zealand.

Reprints: Associate Professor Graham Radford-Smith, Inflammatory Bowel Diseases Laboratory, Bancroft Centre, Queensland Institute of Medical Research, 300 Herston Rd, Herston, 4006, Australia (e-mail: Graham.Radford-Smith@qimr.edu.au).

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (www.ibdjournal.org).

Australian healthy controls were recruited through the Australian Cancer Study, Australian Ovarian Cancer Study, funded by the National Health and Medical Research Council (NHMRC) of Australia (Program Grant, 199600).

Received April 02, 2012

Accepted May 10, 2012

© Crohn's & Colitis Foundation of America, Inc.
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