RUNX3 was recently found to be associated with ulcerative colitis. In this study, downstream target genes of RUNX3 were identified by chromatin immunoprecipitation and promoter sequence microarray chips. Polymorphisms of RUNX3 and its 2 putative downstream (OCTN1 and PPAR-gamma) target genes were genotyped by PCR-SSP and sequencing in 144 Chinese UC patients and 151 healthy controls. Expression of RUNX3 in colonic mucosa of UC patients was detected by immunohistochemical staining. Twelve genes involved in IBD were identified as the downstream target genes of RUNX3. The RUNX3 rs2236851 CT genotype was associated significantly with UC susceptibility and risk of early onset in Chinese population. No association of OCTN1 and PPAR-gamma with UC susceptibility or subphenotypes was identified. RUNX3 expression was significantly increased in UC mucosa. Therefore, RUNX3 might be involved in UC pathogenesis by regulating the expression of genes related with immune response.
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