Suhg Namgoong

Comprehensive Variant Screening of the UGT Gene Family

Purpose UGT1A1, UGT2B7, and UGT2B15 are well-known pharmacogenes that belong to the uridine diphosphate glucuronyltransferase gene family. For personalized drug treatment, it is important to study differences in the frequency of core markers across various ethnic groups. Accordingly, we screened single nucleotide polymorphisms (SNPs) of these three genes and analyzed differences in their frequency among five ethnic groups, as well as attempted to predict the function of novel SNPs. Materials and Methods We directly sequenced 288 subjects consisting of 96 Korean, 48 Japanese, 48 Han Chinese, 48 African American, and 48 European American subjects. Subsequently, we analyzed genetic variability, linkage disequilibrium (LD) structures and ethnic differences for each gene. We also conducted in silico analysis to predict the function of novel SNPs. Results A total of 87 SNPs were detected, with seven pharmacogenetic core SNPs and 31 novel SNPs. We observed that the frequencies of UGT1A1 *6 (rs4148323), UGT1A1 *60 (rs4124874), UGT1A1 *93 (rs10929302), UGT2B7 *2 (rs7439366), a part of UGT2B7 *3 (rs12233719), and UGT2B15 *2 (rs1902023) were different between Asian and other ethnic groups. Additional in silico analysis results showed that two novel promoter SNPs of UGT1A1 -690G>A and -689A>C were found to potentially change transcription factor binding sites. Moreover, 673G>A (UGT2B7), 2552T>C, and 23269C>T (both SNPs from UGT2B15) changed amino acid properties, which could cause structural deformation. Conclusion Findings from the present study would be valuable for further studies on pharmacogenetic studies of personalized medicine and drug response.

Association of VARS2‐SFTA2 polymorphisms with the risk of chronic hepatitis B in a Korean population

Hepatitis B virus (HBV) infection is the most serious risk factor for chronic hepatitis B (CHB), cirrhosis, and hepatocellular carcinoma. Recently, several genome‐wide association studies (GWASs) identified important variants associated with the risk of CHB in Asian populations. Specifically, our previous GWAS identified the VARS2‐SFTA2 gene region as one of the genetic risk loci for CHB.

Replication of genome wide association studies on hepatocellular carcinoma susceptibility loci of STAT4 and HLA-DQ in a Korean population.

A recent genome-wide association study (GWAS) for hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) identified two loci (rs7574865 in STAT4 and rs9275319 in HLA-DQ) in a Chinese population. We attempted to replicate the associations between the two SNP loci and the risk of HCC in a Korean population. The rs7574865 in STAT4 and rs9275319 in HLA-DQ were genotyped in a total of 3838 Korean subjects composed of 287 HBV-related hepatocellular carcinoma patients, 671 chronic hepatitis B virus (CHB) patients, and 2880 population controls using TaqMan genotyping assay. Gene expression was measured by microarray. A logistic regression analysis revealed that rs7574865 in STAT4 and rs9275319 in HLA-DQ were associated with the risk of CHB (OR = 1.25, P = 0.0002 and OR = 1.57, P= 1.44 × 10(-10), respectively). However, these loci were no association with the risk of HBV-related HCC among CHB patients. In the gene expression analyses, although no significant differences in mRNA expression of nearby genes according to genotypes were detected, a significantly decreased mRNA expression in HCC subjects was observed in STAT4, HLA-DQA1, and HLA-DQB1. Although the genetic effects of two HCC susceptibility loci were not replicated, the two loci were found to exert susceptibility effects on the risk of CHB in a Korean population. In addition, the decreased mRNA expression of STAT4, HLA-DQA1, and HLA-DQB1 in HCC tissue might provide a clue to understanding their role in the progression to HCC.

Exonic variants associated with development of aspirin exacerbated respiratory diseases.

Aspirin-exacerbated respiratory disease (AERD) is one phenotype of asthma, often occurring in the form of a severe and sudden attack. Due to the time-consuming nature and difficulty of oral aspirin challenge (OAC) for AERD diagnosis, non-invasive biomarkers have been sought. The aim of this study was to identify AERD-associated exonic SNPs and examine the diagnostic potential of a combination of these candidate SNPs to predict AERD. DNA from 165 AERD patients, 397 subjects with aspirin-tolerant asthma (ATA), and 398 normal controls were subjected to an Exome BeadChip assay containing 240K SNPs. 1,023 models (210-1) were generated from combinations of the top 10 SNPs, selected by the p-values in association with AERD. The area under the curve (AUC) of the receiver operating characteristic (ROC) curves was calculated for each model. SNP Function Portal and PolyPhen-2 were used to validate the functional significance of candidate SNPs. An exonic SNP, exm537513 in HLA-DPB1, showed the lowest p-value (p = 3.40×10−8) in its association with AERD risk. From the top 10 SNPs, a combination model of 7 SNPs (exm537513, exm83523, exm1884673, exm538564, exm2264237, exm396794, and exm791954) showed the best AUC of 0.75 (asymptotic p-value of 7.94×10−21), with 34% sensitivity and 93% specificity to discriminate AERD from ATA. Amino acid changes due to exm83523 in CHIA were predicted to be “probably damaging” to the structure and function of the protein, with a high score of ‘1’. A combination model of seven SNPs may provide a useful, non-invasive genetic marker combination for predicting AERD.

Association study of polymorphisms in interferon-γ receptor genes with the risk of pulmonary tuberculosis.

Tuberculosis (TB) is an infectious disease caused by mycobacterium, which most commonly affects the lungs. The adaptive immune response in Mycobacterium tuberculosis is predominantly mediated by the interferon-γ (IFN-γ) signaling pathway, which is regulated by IFN-γ receptors (IFNGR). IFN-γ activates the transcription of a number of genes that are important in immune responses, thus the appropriate function of IFNGR appears to be important in host defense against mycobacteria. In the present study, 22 genetic variants in IFNGR1 and IFNGR2 were genotyped in 673 patients and 592 normal controls to investigate the association between IFNGR1 and IFNGR2 polymorphisms and the risk of TB. Statistical analyses revealed that four genetic variants in IFNGR1, rs9376269, rs9376268, rs9376267 and rs56251346 were marginally associated with the risk of TB (P = 0.02-0.04), while other single nucleotide polymorphisms in IFNGR1 and IFNGR2 did not exhibit any associations. However, the significance of the four genetic variants rs9376269, rs9376268, rs9376267 and rs56251346 was eliminated following a multiple testing correction of the data (P>0.05). The present results revealed that certain genetic variants in IFNGR genes may be associated with TB development, which may be useful preliminary data for future investigation.

Identification of Novel OCT4 Genetic Variant Associated with the Risk of Chronic Hepatitis B in a Korean Population

Hepatitis B viral infection is a serious risk factor for chronic hepatitis B (CHB), cirrhosis and hepatocellular carcinoma. Recently, several genome‐wide association studies (GWASs) have been conducted to identify important genetic variant associated with the risk of CHB. In our previous GWAS, TCF19 was identified as one of the susceptibility genes for CHB risk (P=4.2×10−9 at rs1419881). In order to discover possible additional causal variants around TCF19, we performed an association study by genotyping single nucleotide polymorphisms (SNPs) in OCT4, a nearby gene to TCF19.

Comparison of genetic variations of the SLCO1B1, SLCO1B3, and SLCO2B1 genes among five ethnic groups.

Organic anion-transporting polypeptide (OATP; gene symbol, SLCO) transporters are generally involved in the uptake of multiple drugs and their metabolites at most epithelial barriers. The pattern of single-nucleotide polymorphisms (SNPs) in these transporters may be determinants of interindividual variability in drug disposition and response. The objective of this study was to define the distribution of SNPs of three SLCO genes, SLCO1B1, SLCO1B3, and SLCO2B1, in a Korean population and other ethnic groups. The study was screened using the Illumina GoldenGate assay for genomic DNA from 450 interethnic subjects, including 11 pharmacogenetic core variants and 76 HapMap tagging SNPs. The genotype distribution of the Korean population was similar to East Asian populations, but significantly different from African American and European American cohorts. These interethnic differences will be useful information for prospective studies, including genetic association and pharmacogenetic studies of drug metabolism by SLCO families.

No association between CCL2 gene polymorphisms and risk of inflammatory demyelinating diseases in a Korean population

Inflammatory demyelinating disease (IDD), which includes multiple sclerosis (MS) and neuromyelitis optica (NMO), affects the central nervous system. Chemokine ligand 2 (CCL2/MCP-1) is considered an important contributor to the development or progression of IDD. However, genetic association studies of Asian populations are lacking. In this study, we investigated a possible association between CCL2 polymorphisms (rs1024611, rs28730833, and rs2857657) and a Korean population (178 IDD patients and 237 healthy controls) using multiple logistic regression models. However, we did not find any association, which was consistent with other studies in Caucasian populations. In conclusion, our results suggest that CCL2 variants may not contribute to the pathogenesis of IDD.

Association analysis of IL7R polymorphisms with inflammatory demyelinating diseases.

Multiple sclerosis (MS) and neuromyelitis optica (NMO), which are referred to as inflammatory demyelinating diseases (IDDs), are autoimmune diseases affecting the central nervous system. Interleukin‑7 receptor (IL7R) encodes for a receptor protein that is important in the development of immune cells. Several studies have reported significant associations between IL7R polymorphisms and MS. The aim of the present study was to investigate a possible association between IL7R polymorphisms and IDDs such as MS and NMO. Thirteen single nucleotide polymorphisms (SNPs) were selected based on their linkage disequilibrium (LD), minor allele frequency (MAF) and location, and were genotyped in 178 IDD patients and 237 healthy controls. The association of SNPs with IDD risk was analyzed by logistic regression. A meta‑analysis on the association between rs6897932 and the risk of MS was also performed. Statistical analyses revealed that a common SNP, rs6897932, was marginally associated with IDD in a recessive model (P=0.003, Pcor.=0.03), which had shown significant associations with MS in previous studies. The results replicated the significant association found between rs6897932 and IDD. In addition, the meta‑analysis of rs6897932 clearly demonstrates a higher magnitude of risk in Asian populations than in Caucasian populations. Although there are certain limitations to our study, the results indicate that the genetic variation of IL7R may be associated with IDDs such as MS and NMO in the population studied.

Identification of additional EHMT2 variant associated with the risk of chronic hepatitis B by GWAS follow-up study

Chronic hepatitis B (CHB) is a precursor to liver cirrhosis and hepatocellular carcinoma, caused by a Hepatitis B viral infection. Genome-wide association studies (GWASs) have been conducted to find genes associated with CHB risk. In previous GWAS, EHMT2 was identified as one of the susceptibility genes for CHB. To further characterize this association and discover possible causal variants, we conducted an additional association study. A total of 11 EHMT2 single-nucleotide polymorphisms (SNP) were selected and genotyped in 3902 subjects (1046 CHB patients and 2856 controls). An additional eight imputed SNPs were also included in further analysis. As a result, rs35875104 showed a strong association with the CHB, along with the previously reported genetic marker for CHB risk, rs652888 (odds ratio (OR) = 0.53, P = 2.20 × 10−8 at rs35875104 and OR = 1.58, P = 9.90 × 10−12 at rs652888). In addition, linkage disequilibrium and conditional analysis identified one SNP (rs35875104) as a novel genetic marker for CHB susceptibility. The GRSs (genetic risk scores) were calculated to visualize the combined genetic effects of all known CHB-associated loci, including EHMT2 rs35875104, which was additionally identified in this study. The findings from the present study may be useful for further understanding of the genetic etiology of CHB.