Functional involvement of RINF during normal myelopoiesis. CD34⁺ myeloid progenitors isolated from 3 healthy donors (A-C) were infected with each of the 4 lentiviral shRNA constructs, either targeting RINF expression (shRNA/RINF-3 and shRNA/RINF-4) or control vectors (empty and shRNA/scramble). The 12 cell populations were then treated in the same conditions with cytokines (IL3 and G-CSF at 20 ng/mL, SCF at 50 ng/mL) to drive them into granulocytes. For each cell population, myeloid differentiation was evaluated, every 2 to 3 days of culture and during several weeks, by cell morphology analysis after cytospin and MGG staining (scale bar, 25 μm). According to the donor, cell differentiation of cultured progenitors developed with different kinetics, and the figure shows morphology of the cell populations at the most informative days recorded, respectively, after 14, 30, and 18 days of culture for donors A, B, and C. Note that cell cultures infected with shRNA–RINF-3 or shRNA–RINF-4 constructs display more immature cells at the promyelocytic/myelocytic stage (indicated by arrows [↑]) than the controls (cell cultures infected with empty or scramble vectors). For donor A, the kinetic of granulocytic differentiation was fast (until day 10), and only a few adherent monocytes/macrophages persisted in control cultures at day 14.