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Title: Understanding inflammatory bowel disease using high-throughput sequencing
Author: de Lange, Katrina Melanie
ISNI:       0000 0004 6350 6818
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2017
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For over two decades, the study of genetics has been making significant progress towards understanding the causes of common disease. Across a wide range of complex disorders there have been hundreds of associated loci identified, largely driven by common genetic variation. Now, with the advent of next-generation sequencing technology, we are able to interrogate rare and low frequency variation in a high throughput manner for the first time. This provides an exciting opportunity to investigate the role of rarer variation in complex disease risk on a genome-wide scale, potentially o↵ering novel insights into the biological mechanisms underlying disease pathogenesis. In this thesis I will assess the potential of this technology to further our understanding of the genetics of complex disease, using inflammatory bowel disease (IBD) as an example. After first reviewing the history of genetic studies into IBD, I will describe the analytical challenges that can occur when using sequencing to perform case-control association testing at scale, and the methods that can be used to overcome these. I then test for novel IBD associations in a low coverage whole genome sequencing dataset, and uncover a significant burden of rare, damaging missense variation in the gene NOD2, as well as a more general burden of such variation amongst known inflammatory bowel disease risk genes. Through imputation into both new and existing genotyped cohorts, I also describe the discovery of 26 novel IBD-associated loci, including a low frequency missense variant in ADCY7 that approximately doubles the risk of ulcerative colitis. I resolve biological associations underlying several of these novel associations, including a number of signals associated with monocyte-specific changes in integrin gene expression following immune stimulation. These results reveal important insights into the genetic architecture of inflammatory bowel disease, and suggest that a combination of continued array-based genome- wide association studies, imputed using substantial new reference panels, and large scale deep sequencing projects will be required in order to fully understand the genetic basis of complex diseases like IBD.
Supervisor: Not available Sponsor: Woolf Fisher Trust ; Cambridge Commonwealth Trust ; Wellcome Trust
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: Inflammatory bowel disease ; Crohn's disease ; Ulcerative colitis ; Genetics ; Next-generation sequencing ; Whole genome sequencing