High Resolution Melting Curve Analysis for High-Throughput SNP Genotyping in IL23R Gene and Association of IL23R with Slovenian Inflammatory Bowel Diseases Patients

Single nucleotide polymorphism (SNP) analysis is important tool in the studies of genetic factors associated with complex diseases and with genetically influenced response to drug therapy (pharmacogenetics). Recently, a new generation of generic dsDNA binding dyes (LCGreenTM) contributed to the development of fast and low-cost method for SNP detection and/or genotyping based on high resolution melting (HRM) analysis. The aim of our study was to develop HRM assay for IL23R gene (rs7517847) and to perform association study in Slovenian inflammatory bowel diseases (IBD) patients. We genotyped 345 Slovenian healthy controls and 295 IBD patients including 159 with Crohn’s disease (CD) and 136 with ulcerative colitis (UC) for rs7517847 polymorphism in IL23R gene using standard RFLP and optimized HRM methods. In this study, we showed, that HRM is a simple, fast and reliable method for genotyping of clinical samples where homozygotes (GG and TT) were determined by »Tm calling method« and difference between homozygotes and heterozygotes was determined by different melting curve shape using »gene scanning method«. With combination of results from »Tm calling« and »gene scanning« methods, we achieved 98,6% concordance between PCR-RFLP and PCRHRM results, based on the analysis of 640 samples. We found statistically significant association of IL23R polymorphism with Slovenian Crohn’s disease patients when comparing genotype and allele frequencies between CD patients and controls. Allele frequency of minor allele G was 0,46 in controls and was reduced to 0,33 in CD patients (p < 0,001, OR = 0,588). The frequency of T/T genotype carriers was higher in CD patients (50,3%) than in controls (26,7%, p = 0,002, OR = 2,558). We found weak association between IL23R polymorphism and Slovenian UC patients. Carriers of T/T genotype have higher risk for UC (p = 0,035, OR = 1,599). These results suggest IL23R plays important role in CD and UC development in Slovenian patients.