Fig. 6. Flow-cytometry analysis of GPA surface expression in NACA- and EGFP-transduced CD34⁺ cells along differentiation of the erythroid lineage. 72 hours after the initiation of transduction, CD34⁺ cells were cultured under conditions optimized for erythroid-cell growth and maturation. Cell suspensions were stained at the indicated days of culture [day 5 (D5), day 7 (D7) and day 9 (D9)] with an anti-GPA-PE mAb and analysed by flow cytometry for cell-surface expression of GPA. (A) Unfilled profiles represent GPA expression by EGFP-transduced cells and filled profiles represent GPA expression by NACA-transduced cells. Isotype-matched control mAb was used in all experiments to set the parameters for analysis. Positive GPA fluorescence (gate M1) is set according to the isotype-matched control mAb. One representative experiment out of three performed is shown. (B) Results are expressed as the proportion of GPA cell-surface-marker-positive cells present in the cell culture.