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Myeloid development is selectively disrupted in PU.1 null mice
K L Anderson1, K A Smith, K Conners
1The Burnham Institute, La Jolla, CA, USA.
Abstract:
The ets family transcription factor PU.1 is expressed in monocytes/macrophages, neutrophils, mast cells, B cells, and early erythroblasts, but not in T cells. We have recently shown that PU.1 gene disruption results in mice with no detectable monocytes/macrophages and B cells but T-cell development is retained. Although neutrophil development occurred in these mice, it was delayed and markedly reduced. We now proceed to demonstrate that PU. 1 null hematopoietic cells fail to proliferate or form colonies in response to macrophage colony-stimulating factor (M-CSF), granulocyte CSF (G-CSF), and granulocyte/macrophage CSF (GM-CSF). In contrast, PU.1 null cells did proliferate and form colonies in response to interleukin-3 (IL-3), although the response was reduced as compared with control littermates. Compared with control cells, PU.1 null cells had minimal expression of G- and GM-CSF receptors and no detectable M-CSF receptors. The size of individual myeloid colonies produced from PU.1 null primitive and committed myeloid progenitors in the presence of IL-3, IL-6, and stem cell factor (SCF) were reduced compared with controls. Under these conditions, PU.1 null progenitors produced neutrophils but not monocytes/macrophages. These observations suggest that PU.1 gene disruption induces additional cell-autonomous effects that are independent of the alterations in myeloid growth factor receptor expression. Our results demonstrate that PU.1 gene disruption affects a number of developmentally regulated hematopoietic processes that can, at least in part, explain the changes in myeloid development and reduction in myeloid and neutrophil expansion observed in PU.1 null mice.
Insights
The transcription factor PU.1 is crucial for myeloid and B-cell development. PU.1 gene disruption impairs hematopoietic stem cell proliferation and myeloid progenitor function, impacting neutrophil and monocyte/macrophage development.
Area of Science:
- Hematology
- Molecular Biology
- Immunology
Background:
- The ets family transcription factor PU.1 is essential for the development of various hematopoietic cell lineages.
- PU.1 expression is detected in monocytes/macrophages, neutrophils, mast cells, B cells, and early erythroblasts, but not in T cells.
- Previous studies showed PU.1 gene disruption leads to absence of monocytes/macrophages and B cells, with retained T-cell development and impaired neutrophil development.
Purpose of the Study:
- To investigate the functional consequences of PU.1 gene disruption on hematopoietic stem and progenitor cells.
- To elucidate the role of PU.1 in myeloid cell proliferation and differentiation in response to specific growth factors.
- To determine the impact of PU.1 deficiency on myeloid growth factor receptor expression and cell-autonomous effects.
Main Methods:
- Analysis of PU.1 null hematopoietic cells' proliferation and colony formation in response to various cytokines (M-CSF, G-CSF, GM-CSF, IL-3).
- Assessment of myeloid growth factor receptor expression (M-CSF, G-CSF, GM-CSF receptors) in PU.1 null cells.
- Evaluation of myeloid progenitor colony size and cell type production (neutrophils, monocytes/macrophages) under specific cytokine conditions (IL-3, IL-6, SCF).
Main Results:
- PU.1 null hematopoietic cells failed to proliferate or form colonies in response to M-CSF, G-CSF, and GM-CSF.
- PU.1 null cells showed reduced proliferation in response to IL-3 and had minimal/undetectable expression of corresponding CSF receptors.
- PU.1 null myeloid progenitors produced smaller colonies and generated neutrophils but not monocytes/macrophages, suggesting cell-autonomous effects beyond receptor alterations.
Conclusions:
- PU.1 gene disruption profoundly affects hematopoietic stem and progenitor cell function, leading to impaired myeloid development.
- The absence of PU.1 results in reduced myeloid expansion and altered neutrophil development, partly due to impaired receptor expression and cell-autonomous effects.
- PU.1 is critical for regulating developmentally programmed hematopoietic processes essential for myeloid lineage commitment and expansion.