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Poster presentations: Genetics 2020

P822 Genetic analysis of ulcerative colitis in Japanese individuals using population-specific SNP array

D. Okamoto1, Y. Kakuta1, N. Takeo1, R. Moroi1, M. Kuroha1, Y. Kanazawa1, S. Hisashi1, Y. Fuyuno2, J. Umeno2, A. Hirano2, T. Torisu2, M. Nakamura3, M. Esaki4, T. Matsumoto5, Y. Kinouchi1, A. Masamune1

1Tohoku University Graduate School of Medicine, Division of Gastroenterology, Sendai, Japan, 2Graduate School of Medical Sciences- Kyusyu University, Department of Medicine and Clinical Science, Fukuoka, Japan, 3National hospital organization NHO Nagasaki Medical Center, Clinical Research Center, Omura, Japan, 4Saga University, Department of Endoscopic Diagnostics and Therapeutics, Saga, Japan, 5Iwate Medical University, Division of Gastroenterology- Department of Internal Medicine- Faculty of Medicine, Morioka, Japan

Background

Previous genome wide association studies (GWASs) have identified over 200 susceptibility loci for inflammatory bowel diseases (IBD), but studies in non-European population are limited. To clarify the genetic background of ulcerative colitis (UC) in the Japanese population, we conducted GWAS using a population specific SNP array (Japonica Array).

Methods

Discovery GWAS included 624 UC patients and 2004 healthy controls (HC) and replication study included 1075 UC patients and 419 HCs. We performed GWAS using a Japonica Array and the subsequent imputation with a Japanese population reference panel (referred to as 2KJPN). After GWAS, significant and candidate loci were identified and the representative top SNPs of each region were analysed in replication study and combined analysis. The probability of colectomy between genotypes of rs117506082, the top hit SNP at HLA loci, was analysed using the Kaplan–Meier method.

Results

In the GWAS, only the HLA loci showed genome wide significant association [rs117506082, p = 6.69E−28, OR=1.29, 95%CI=1.23–1.35]. 7 regions with nominal significance included 2 known loci: IL23R [rs76418789, p = 6.29E−7, OR=0.89, 95%CI=0.85–0.93], IRF8 [rs16940202, p = 1.03E−6, OR=1.07, 95%CI=1.04–1.10] and 5 novel loci: miR-622 [rs9560575, p = 8.23E−7, OR=1.06, 95%CI=1.04–1.09], 14q31 [rs117618617, p = 1.53E−6, OR=1.13, 95%CI=1.09–1.19], KAT6B [rs12260609, p = 1.81E−6, OR=1.06, 95%CI=1.04–1.09], PAX3-CCDC140-SGPP2 [rs7589797, p = 2.87E−6, OR=0.94, 95%CI=0.93–0.97], KCNA2 [rs118020656, p = 4.01E−6, OR=1.12, 95%CI=1.07–1.18]. Combined analysis revealed that the HLA loci [rs117506082, p = 1.10E−23, OR=3.43, 95%CI=2.99–3.83] and IL23R p.G149R [rs76418789, p = 9.03E−11, OR=0.51, 95%CI=0.42–0.63] had a genome wide significant association. The GG genotype of rs117506082 had a significantly lower probability for total colectomy compared with the GA+AA genotype (p = 1.72E−2).

Conclusion

IL23R p.G149R is a susceptibility locus for UC in Japanese individuals. The GG genotype of rs117506082 at HLA loci, a risk genotype for UC susceptibility, may predict a better clinical course.