Critical role of P1-Runx1 in mouse basophil development

Abstract

Abstract Runx1 P1N/P1N mice are deficient in the transcription factor distal promoter-derived Runt-related transcription factor 1 (P1-Runx1) and have a > 90% reduction in the numbers of basophils in the BM, spleen, and blood. In contrast, Runx1P1N/P1N mice have normal numbers of the other granulocytes (neutrophils and eosinophils). Although basophils and mast cells share some common features, Runx1P1N/P1N mice have normal numbers of mast cells in multiple tissues. Runx1P1N/P1N mice fail to develop a basophil-dependent reaction, IgE-mediated chronic allergic inflammation of the skin, but respond normally when tested for IgE- and mast cell–dependent passive cutaneous anaphylaxis in vivo or IgE-dependent mast cell degranulation in vitro. These results demonstrate that Runx1P1N/P1N mice exhibit markedly impaired function of basophils, but not mast cells. Infection with the parasite Strongyloides venezuelensis and injections of IL-3, each of which induces marked basophilia in wild-type mice, also induce modest expansions of the very small populations of basophils in Runx1P1N/P1N mice. Finally, Runx1P1N/P1N mice have normal numbers of the granulocyte progenitor cells, SN-Flk2+/−, which can give rise to all granulocytes, but exhibit a > 95% reduction in basophil progenitors. The results of the present study suggest that P1-Runx1 is critical for a stage of basophil development between SN-Flk2+/− cells and basophil progenitors.