The human CD34 PAC54A19 (18 kb 5′ upstream) is coexpressed with early hematopoietic surface markers in bone marrow and down-regulated with differentiation.

Bone marrow cells were stained with anti–human CD34 antibody and a second marker as indicated and subjected to fluorescence cytometry. The vertical axes represent human CD34 fluorescence in all panels. The percent of positive cells in each quadrant is noted. Dead cells were gated out following staining with PI. The data shown were obtained from one of the MluI-digested PAC54A19 founders. A similar pattern was observed in the 3 other PAC54A19 founder lines, as well as in the larger (−48, −31, and −23 kb) constructs shown in Figure1.