The effect of the -521 C/T SNP on the transcriptional activity of the DRD4 minimal promoter in neural cell lines. No significant difference could be detected between the transcriptional activities of the pDRD4-C constructs possessing the -521 C or T alleles in any of these cell lines. Luciferase activity was normalized to the β-galactosidase activity. Data are presented as fold increments over the pGL3-Basic activity and shown as mean ± SD. Results of a representative experiment are shown as measured in triplicates. Similar data were obtained from three independent transfection experiments.