The transcriptional effect of an A-to-G polymorphism identified in the ferrochelatase promoter of patients with protoporphyria.

(A) Summary of the HPRT targeting constructs used to assess the effect of A or G polymorphism located at −251 bp from the start codon. The G haplotype was introduced into the −1.1 kb reporter gene construct by PCR amplification of this region from genomic DNA from a patient with protoporphyria known to have the G polymorphism. The −1.1 kb fragment was then cloned into the EGFP reporter gene vector (−1.1 A to G). (B) Cells containing either the A polymorphism or the G polymorphism were differentiated for 3 days in primary culture. The embryoid bodies were disrupted by brief trypsinization, and EGFP expression was determined in live cells using flow cytometry. The EGFP intensities for the −0.125 (control transgene), the −1.1 kb or the −1.1 A to G transgenes were determined using maximal peak heights and are noted to the right of each histogram.