Analysis of candidate genes RUNX3 and THEMIS

BONDAR, CONSTANZA; PLAZA-IZURIETA, LETICIA; FERNANDEZ-JIMENEZ, NORA; CASTELLANOS-RUBIO, AINARA; IRASTORZA, IÑAKI; VITORIA, JUAN CARLOS; CHIRDO, FERNANDO; BILBAO, JOSE RAMON

Simposio; 14th International Coeliac Disease Symposium 2011; 2011

OBJECTIVES: Coeliac disease (CD) is a multigenic disorder where HLA-DQ2/DQ8, the most important genetic factor, contribute about 35% to genetic risk. Recently, Genome-Wide Association studies (GWAs) have found more than 26 regions for CD susceptibility, in which several differentially expressed genes have been previously reported. The aim of this work was to evaluate the allelic association and expression of two candidate genes, RUNX3 and THEMIS, which meet functional and positional requirements. RUNX3 is a transcription factor involved in processes such as haematopoiesis, thymopoiesis and dendritic cell maturation, also acting as tumour suppressor in gastric cancer. THEMIS is a T cell specific protein important for late thymocyte development. METHODS: We genotyped SNPs rs1093122 and rs80273 for RUNX3 and THEMIS regions respectively, in 532 controls and 538 coeliac patients, using TaqMan probes and primers on an ABI Prism 7900HT instrument. SDS v2.3 software was used for genotype calling. Association analyses were performed using 2x2 contingency tables. Biopsy specimens from distal duodenum were obtained from 25 paediatric patients at diagnosis and after 2 years on gluten free diet, and from 8 non-CD controls. Expression was quantified by RT-PCR with 8ng of total RNA. RESULTS: Genotyping of both SNPs did not show allelic or genotypic association to CD in our population. Expression of RUNX3 and THEMIS was significantly higher in biopsies from untreated CD patients compared to samples obtained after GFD, and to controls (p<0,01). Correlation studies between genotypes and mRNA expression levels in coeliac patients did not show a significant coefficient in neither of both genes. CONCLUSIONS: Though there are no clear functional associations between THEMIS and CD, it was recently reported that RUNX3 regulates the expression of gamma-IFN, perforin, and granzyme B, critical elements of the effector CTL program, that could be related to CD pathogenesis and deserve further investigation.