Growth factor independence 1 (Gfi1) regulates cell-fate decision of a bipotential granulocytic-monocytic precursor defined by expression of Gfi1 and CD48.

The transcriptional repressor Gfi1 regulates the expression of genes important for survival, proliferation and differentiation of hematopoietic cells. Gfi1 deficient mice are severely neutropenic and accumulate ill-defined CD11b(+)GR1(int) myeloid cells. Here we show that Gfi1 expression levels determine mono- or granulocytic lineage choice in precursor cells. In addition, we identify CD48 as a cell surface marker which enables a better definition of monocytes and granulocytes in mouse bone marrow. Using the CD48/Gr1/Gfi1 marker combination we can show that the CD11b(+)GR1(int) cells accumulating in Gfi1 deficient mice are monocytes and not granulocyte precursors. Expression of CD48, Gr1 and Gfi1 define different bone marrow subpopulations that are either committed to the granulocytic lineage, or bipotential precursors of granulocytes or monocytes. Finally, a comparison of genes differentially expressed between murine Gfi1 high granulocytic precursors and mature granulocytes with gene expression changes from human myeloblasts versus neutrophils show a strong resemblance of human and mouse differentiation pathways. This underlines the value of the markers CD48 and Gfi1 identified here to study human and murine granulo-monocytic differentiation.