Open AccessLimited Evidence for Parent-of-Origin Effects in Inflammatory Bowel Disease Associated Loci
Author(s) -
Karin Fransén,
Mitja Mitrovič,
Cleo C. van Diemen,
B.K. Thelma,
Ajit Sood,
André Franke,
Stefan Schreiber,
Vandana Midha,
Garima Juyal,
Uroš Potočnik,
Jingyuan Fu,
Ilja M. Nolte,
Rinse K. Weersma
Publication year - 2012
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0045287
Subject(s) - inflammatory bowel disease , allele , genetics , locus (genetics) , ulcerative colitis , genome wide association study , biology , heritability , genetic predisposition , genotype , medicine , disease , immunology , gene , single nucleotide polymorphism
Background Genome-wide association studies of two main forms of inflammatory bowel diseases (IBD), Crohn’s disease (CD) and ulcerative colitis (UC), have identified 99 susceptibility loci, but these explain only ∼23% of the genetic risk. Part of the ‘hidden heritability’ could be in transmissible genetic effects in which mRNA expression in the offspring depends on the parental origin of the allele (genomic imprinting), since children whose mothers have CD are more often affected than children with affected fathers. We analyzed parent-of-origin (POO) effects in Dutch and Indian cohorts of IBD patients. Methods We selected 28 genetic loci associated with both CD and UC, and tested them for POO effects in 181 Dutch IBD case-parent trios. Three susceptibility variants in NOD2 were tested in 111 CD trios and a significant finding was re-evaluated in 598 German trios. The UC-associated gene, BTNL2 , reportedly imprinted, was tested in 70 Dutch UC trios. Finally, we used 62 independent Indian UC trios to test POO effects of five established Indian UC risk loci. Results We identified POO effects for NOD2 (L1007fs; OR = 21.0, P-value = 0.013) for CD; these results could not be replicated in an independent cohort (OR = 0.97, P-value = 0.95). A POO effect in IBD was observed for IL12B (OR = 3.2, P-value = 0.019) and PRDM1 (OR = 5.6, P-value = 0.04). In the Indian trios the IL10 locus showed a POO effect (OR = 0.2, P-value = 0.03). Conclusions Little is known about the effect of genomic imprinting in complex diseases such as IBD. We present limited evidence for POO effects for the tested IBD loci. POO effects explain part of the hidden heritability for complex genetic diseases but need to be investigated further.