Luciferase reporter assay to assess enhancer function in rs2069837 and the effect of HDAC inhibition. (A) The intronic sequence with A or G (hg19 chr7:22767927–22768177) was inserted between XbaI and EcoRI, while the promoter sequence (nucleotides −303 to +12, Ensembl ENSG00000136244) was inserted between SPEI and MluI. (B) No increase in luciferase expression was observed in promoter-only vector. Significantly increased luciferase expression was detected in both vectors with intronic sequence (A/G), with significantly higher expression in the construct with G allele than that with A allele (p<0.05). (C) TSA treatment increased luciferase expression in both constructs with intronic sequence (A/G) compared with DMSO-treated samples. In the presence of TSA, the luciferase expression was significantly higher in the construct with A allele than that with G allele (p<0.05). DMSO, dimethyl sulfoxide; HDAC, histone deacetylase; TSA, Trichostatin A.