Sorting for GFP of BM cells from the Meis1^em1Bcca/Meis1^wtmice efficiently enriches long-term engrafting cells and hematopoietic progenitor cells. (A) Experimental design. Cells (5000 GFP⁺ or 200 000 GFP⁻) from the Meis1^em1Bcca/Meis1^wt mice (CD45.2) were transplanted into lethally irradiated recipients (CD45.1 × CD45.2) together with 200 000 competitor BM cells (CD45.1). (B) Flow cytometric analysis of the cell mixture before injection (CD45.2 marks cells from Meis1^em1Bcca/Meis1^wt mice and CD45.1 marks cells from control mice). (C) A representative flow cytometric plot of percentages of donor-derived cells in recipient mouse PB 4 weeks posttransplantation. (D) PB donor chimerism during 4-month engraftment (N = 6). The percentage of donor-derived cells from sorted GFP⁺ cells, from Meis1^em1Bcca/Meis1^wt mice (CD45.2) vs competitor control cells (CD45.1) increases dramatically over the 4 months, where the sorted GFP⁻ cells are barely engrafted.