Intrinsic requirement for zinc finger transcription factor Gfi-1 in neutrophil differentiation.

We report essential roles of zinc finger transcription factor Gfi-1 in myeloid development. Gene-targeted Gfi-1(-/-) mice lack normal neutrophils and are highly susceptible to abscess formation by gram-positive bacteria. Arrested, morphologically atypical, Gr1(+)Mac1(+) myeloid cells expand with age in the bone marrow. RNAs encoding primary but not secondary or tertiary neutrophil (granulocyte) granule proteins are expressed. The atypical Gr1(+)Mac1(+) cell population shares characteristics of both the neutrophil and macrophage lineages and exhibits phagocytosis and respiratory burst activity. Reexpression of Gfi-1 in sorted Gfi-1(-/-) progenitors ex vivo rescues neutrophil differentiation in response to G-CSF. Thus, Gfi-1 not only promotes differentiation of neutrophils but also antagonizes traits of the alternate monocyte/macrophage program.