Identification of three genes up-regulated in PU.1 rescued monocytic precursor cells

The requirement of the transcription factor PU.1 for macrophage development has been well documented. However, the target genes regulated by PU.1 controlling macrophage maturation are not known. A granulocyte macrophage colony stimulating factor (GM-CSF)-dependent PU.1 null monocytic precursor cell was stably transduced with a PU.1-expressing retrovirus. The expression of PU.1 altered the surface expression of a few proteins expressed on monocytes; these cells, however, remained GM-CSF dependent and maintained an immature phenotype. In contrast to the PU.1 null cells, the cells expressing PU.1 responded to macrophage colony stimulating factor (M-CSF) with subsequent development into mature macrophages. Using suppressive subtractive hybridization between the PU.1 null and immature PU.1 rescued cells, three genes, MRP-14, Dap12 and CD53, were found expressed in the rescued cells, but not in the PU.1 null cells. In addition, these genes were modulated during M-CSF-induced maturation of the PU.1 rescued cells. The PU.1 null and rescued early monocytic cells provide a useful model to study the role of PU.1 in macrophage development.