Erythroid-Specific Expression in Secondary Mice
(A) UROS activity in whole BM and in Ter-119⁺- and Ter-119⁻-sorted BM cells 20 weeks after transplantation from wild-type (+/+), CEP-deficient mice (CEP), and secondary recipients (CEPII).
(B) Percentage of fluorocytes monitored over time by FACS from all groups.
(C) Level of urinary-porphyrin accumulation in different groups of mice determined by HPLC.
Values represent mean ± SD.

Selective Advantage of Corrected Erythropoietic Cells
(A) Schematic representation of the proviral form of the three SIN lentiviral vectors. The first two are constitutive vectors expressing GFP from the LTR-derived MND or the human cellular EF1α promoter. The third is a bipromoter vector coexpressing UROS cDNA from the erythroid HS40/Ank promoter and GFP from the EF1α promoter.
(B) GFP expression in red blood cells (RBCs) and white blood cells (WBCs), 4 and 12 weeks after BM transplantation. The dots correspond to individual CEP mice transplanted with HSCs transduced at five different MOIs (2, 6, 20, 60, and 80) either with the EFpGFP (○) or with the ESpUROS-EFpGFP (◆) vector. Arrows emphasize the difference in the slopes of the curves obtained with the two vectors, reflecting the survival advantage of corrected RBCs.
(C) Relation between the percentage of fluorocytes and the percentage of GFP⁺ RBCs at 4 and 12 weeks. CEP mice were transplanted with HSCs transduced with the therapeutic ESpUROS-EFpGFP vector.

Level of Transduction Necessary to Obtain a Complete Correction of the Phenotype
CEP mice were transplanted with HSCs transduced with the therapeutic ESpUROS-EFpGFP vector (same experiments as in Figure 4C), and the percentages of fluorocytes and GFP⁺ WBCs were determined for each mouse at 4 and 12 weeks. In the right part, skin photosensitivity was assayed 20 weeks after transplantation: (◆), mice with severe skin photosensitivity; (), mice with mild photosensitivity; and (◇) mice without any macroscopic or microscopic lesions.

Enzymatic, Metabolic, and Phenotypic Correction of Transplanted Mice
(A) Schematic representation of the proviral form of the erythroid-specific SIN lentiviral vector ESpUROS. The following abbreviations are used: ΔU3, U3 region deleted of tata box and enhancer sequences; cPPT, central polypurine tract; CTS, central termination sequence; Δgag, truncated gag region; SA, splice acceptor site; SD, splice donor site; HS40, enhancer of the human α-globin gene; Ankp, ankyrin promoter of the human ankyrin gene; UROS, cDNA of uroporphyrinogene III synthase; and WPRE, woodchuck posttranscriptional regulatory element. The WPRE probe for Southern-blot analysis is indicated.
(B) UROS activity in BM cells 20 weeks after transplantation from unmanipulated wild-type BALB/cJ mice (+/+), from deficient CEP mice (CEP), and from the three treated groups of mice (groups I to III).
(C) Level of urinary-porphyrin accumulation in the different groups of mice determined by HPLC.
(D) Representative FACS analysis of the percentage of fluorocytes in peripheral blood from one mouse in each group of controls or treated mice.
(E) Percentage of fluorocytes monitored over time by FACS in all groups.
Values represent mean ± standard deviation (SD).

Cell-Therapy Experiments
(A) Percentage of fluorocytes monitored over time by FACS in the CEP-deficient mice (CEP) and mice treated by BM transplantation: BMT 15% (15% of normal cells mixed with 85% of deficient cells), BMT 30%, BMT 45% and BMT 60%. (B) Hematological parameters (RBCs, hemoglobin, hematocrit and reticulocyte counts) were analyzed for the different groups of mice 24 weeks after transplantation.

Selective Advantage of Corrected Cells of the Erythroid Lineage
(A) Representative FACS analysis of BM cells and peripheral RBCs from each group of mice. BM cells were analyzed for Ter-119 expression, and three different groups were differentiated by their SSC and FSC profiles (upper left part): (I) RBCs, (II) intermediate normoblasts, and (III) early normoblasts. BM cells were also analyzed for Gr-1 expression (upper middle part). GFP expression was then analyzed in each population of erythroid (Ter-119) and myeloid (Gr-1) BM cells and in peripheral RBCs (right part).
(B) Ratio of the percentage of GFP expression between the different populations of erythropoietic cells and Gr-1-positive cells. ^∗p < 0.01 versus MNDpGFP vector in normal mice; ^∗∗p < 0.001 versus EFpGFP vector in normal and CEP mice; ^∗∗∗p < 0.001 versus ESpUROS-EFpGFP vector in the different populations of erythropoietic cells of CEP mice.
Values for (B) represent mean ± SD.