Abstract
AbstractTargeted disruption of the Friend leukemia integration 1 (Fli-1) proto-oncogene results in severe dysmegakaryopoiesis and embryonic lethality. We used morula-stage aggregation as a strategy to further clarify the hematopoietic defects of the Fli-1 gene-targeted mice. Analyses of lineage expression of Fli-1+/- and Fli-1-/- cells in the peripheral blood and bone marrow of chimeric mice consistently demonstrated reduced numbers of neutrophilic granulocytes and monocytes and increased numbers of natural killer (NK) cells. Transplantation studies using sorted Fli-1 mutant cells produced similar findings. Clonal culture studies of bone marrow cells revealed increased numbers of granulocytic and early erythroid progenitors in the Fli-1+/- cells. The sorted Fli-1-/- bone marrow cells revealed specific down-regulation of CCAAT/enhancer binding protein-α (C/EBPα) and C/EBPϵ, and the receptors for granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage CSF (GM-CSF), consistent with their critical roles in granulopoiesis. Collectively, these observations suggest previously unknown physiologic roles for Fli-1 in granulocytic, erythroid, and NK cell proliferation and differentiation. Production of chimeras by morula-stage embryo aggregation is an effective way to unravel cell-autonomous hematopoietic defects in gene-targeted mice.
Highlights
The Friend leukemia integration 1 (Fli-1) proto-oncogene is a member of the Ets gene family of transcription factors, which bind to DNA elements containing the consensus sequence GGA(A/T).[1,2,3] Fli-1 is preferentially expressed in cells of hematopoietic lineages and vascular endothelial cells, and has been shown to transactivate such genes as GATA-1,1,2 glycoprotein IIb,[4,5,6] gpVI,[7] gpIX,[8] gpIb,[8] and c-MPL.[9]
We demonstrated that the expression of genes previously shown to be critical for granulopoiesis is reduced in the bone marrow (BM) cells derived from the Fli-1 mutant
Chimeric mice On the basis of polymerase chain reaction (PCR) analysis of sorted Ly-5.2 cells, we identified a total of 10 chimeric mice, 1 with WT Ly-5.2 cells, 7 with Fli-1ϩ/Ϫ Ly-5.2 cells, and 2 with Fli-1Ϫ/Ϫ Ly-5.2 cells
Summary
The Friend leukemia integration 1 (Fli-1) proto-oncogene is a member of the Ets gene family of transcription factors, which bind to DNA elements containing the consensus sequence GGA(A/T).[1,2,3] Fli-1 is preferentially expressed in cells of hematopoietic lineages and vascular endothelial cells, and has been shown to transactivate such genes as GATA-1,1,2 glycoprotein (gp) IIb,[4,5,6] gpVI,[7] gpIX,[8] gpIb,[8] and c-MPL.[9]. We noted that livers of the E11.0 Fli-1Ϫ/Ϫ embryos were pale and contained primarily polychromatophilic and orthochromatic normoblasts.[12] To further define the roles of Fli-1 in hematopoiesis in individuals with longer viability, we generated Fli-1 chimeric mice by morula-stage embryo aggregation between Ly-5.2 Fli-1 heterozygote (Fli-1ϩ/Ϫ) intercross embryos and wild-type (WT) Ly-5.1 embryos. Such chimeras were rescued from the embryonic lethality and could be studied for Fli-1–associated cell-autonomous defects. These observations suggest that the Fli-1 gene plays important roles in myelomonocytic, erythroid, and NK cell development
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