Limited Evidence for Parent-of-Origin Effects in Inflammatory Bowel Disease Associated Loci
PLOS ONE
Authors: Fransen, Karin; Mitrovic, Mitja; van Diemen, Cleo C.; Thelma, B. K.; Sood, Ajit; Franke, Andre; Schreiber, Stefan; Midha, Vandana; Juyal, Garima; Potocnik, Uros; Fu, Jingyuan; Nolte, Ilja; Weersma, Rinse K.
Abstract
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 similar to 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.
Association of a polymorphism of BTN2A1 with dyslipidemia in East Asian populations
EXPERIMENTAL AND THERAPEUTIC MEDICINE
Authors: Fujimaki, Tetsuo; Kato, Kimihiko; Oguri, Mitsutoshi; Yohida, Tetsuro; Horibe, Hideki; Yokoi, Kiyoshi; Watanabe, Sachiro; Satoh, Kei; Aoyagi, Yukitoshi; Tanaka, Masashi; Yoshida, Hiroto; Shinkai, Shoji; Nozawa, Yoshinori; Shin, Dong-Jik; Lee, Jong Ho; Jang, Yangsoo; Yamada, Yoshiji
Abstract
We previously identified rs6929846 of the butyrophilin, subfamily 2, member Al gene (BTN2A1) as a susceptibility locus for myocardial infarction in Japanese individuals by a genome-wide association study. The aim of the present study was to examine the relation of the rs6929846 polymorphism of BTN2A1 to dyslipidemia in Japanese and Korean populations, given that clyslipidemia is an important risk factor for myocardial infarction. A total of 10,953 individuals from three independent subject panels were examined. The relations of the rs6929846 polymorphism of BTN2A1 to serum concentrations of triglycerides, high-density lipoprotein (HDL)-cholesterol and low-density lipoprotein (LDL)-cholesterol were examined in each subject panel. The C T polymorphism (rs6929846) of BTN2A1 was significantly associated with serum concentrations of triglycerides in Japanese subject panels A (P=0.0004) and B (P=0.0010), and in the Korean population (P=0.0095), with the minor T allele being related to an increased serum concentration of triglycerides. The rs6929846 was associated with serum concentrations of HDL-cholesterol in Japanese subject panels A (P=0.0047) and B (P=0.001.5), with the T allele being related to a decreased serum concentration of HDL-cholesterol, but not in the Korean population. This polymorphism was associated with the serum concentration of LDL-cholesterol only in Japanese subject panel B (P=0.0059), with the T allele being related to an increased serum concentration of LDL-cholesterol. The results suggest that BTN2A1 may be a susceptibility gene for hypertriglyceridemia in East Asian populations and for low serum HDL-cholesterol in the Japanese population.