Reporter gene constructs used to generate transgenic mouse lines. The structure of the constructs used to generate the −0.15 TG and −4.0 TG lines are shown. Construct −0.15 TG contains the minimal human ferrochelatase promoter containing two Sp1-like elements, and construct −4.0 TG contains the minimal promoter, the erythroid enhancer elements GATA, and NF-E2 and approximately 3.5 kb of upstream sequence. Both promoter constructs drive the expression of the luciferase reporter gene.