Block of myeloid differentiation induced by X-RARα. Sca1+/lin- HSCs were transduced with PML/RARα or PLZF/RARα. Mock-transduced cells were used as control. The cells were seeded in semisolid medium ± G/GM-CSF for the induction of granulocytic/monocytic differentiation. At day 10 the cells were harvested and analyzed. (A) Morphologic analysis of cells stained with May-Grünwald-Giemsa. Original magnification, × 400. (B) Differentiation-specific surface marker expression. Gr-1 and Mac-1 are markers for myeloid differentiation and Sca1 and c-kit are stem cell markers. One representative experiment of 3 is given.