Promoter Polymorphism of the EED Gene Is Associated with the Susceptibility to Ulcerative Colitis

Embryonic ectoderm development (EED) protein is involved in multiple cellular protein complexes. EED mediates the repression of gene activity through histone deacetylation, and it may act as a specific regulator of integrin's function. This gene was identified as a candidate gene for the susceptibility to IBD by our previous cDNA microarray analysis. The present study aimed to validate the expression level of the EED gene in patients with IBD by performing RT-PCR, and we investigated whether the polymorphisms in the EED gene are associated with the susceptibility to UC, and whether a functional EED promoter polymorphism is related to UC. Genotype analysis of the EED SNPs was performed by single-base extension analysis. The haplotype frequencies of the EED gene for multiple loci were estimated using the expectation maximization algorithm. The promoter region of the human EED gene, including the g.-1850G > C allele, was isolated by PCR. The amplified PCR products were inserted into the pGL3-basic vector and the luciferase activity was analyzed. The expression level of the EED gene was significantly decreased in both the UC and CD patients and it was significantly higher in the liver and ileum than in the other tissues of the human digestive system. The genotype and allele frequencies of the g.-1850G > C polymorphism of the EED gene in the UC patients were significantly different from those of the healthy controls (p = 0.018 and 0.017, respectively). The luciferase activity assay showed that the promoter activity was decreased about twofold in the construct containing the g.-1850G allele compared to that of the construct containing the g.-1850C allele, which means that the allele G could produce less EED mRNA. These results suggest that the g.-1850G > C polymorphism in the EED gene might be associated with the susceptibility to UC by the change of the EED expression level.