Mouse neutrophilic granulocytes express mRNA encoding the macrophage colony-stimulating factor receptor (CSF-1R) as well as many other macrophage-specific transcripts and can transdifferentiate into macrophages in vitro in response to CSF-1

Abstract

The differentiation of macrophages from their progenitors is controlled by macrophage colony-stimulating factor (CSF-1), which binds to a receptor (CSF-1R) encoded by the c-fms proto-oncogene. We have previously used the promoter region of the CSF-1R gene to direct expression of an enhanced green fluorescent protein (EGFP) reporter gene to resident macrophage populations in transgenic mice. In this paper, we show that the EGFP reporter is also expressed in all granulocytes detected with the Gr-1 antibody, which binds to Ly-6C and Ly-6G or with a Ly-6G-specific antibody. Transgene expression reflects the presence of CSF-1R mRNA but not CSF-1R protein. The same pattern is observed with the macrophage-specific F4/80 marker. Based on these findings, we performed a comparative array profiling of highly purified granulocytes and macrophages. The patterns of mRNA expression differed predominantly through granulocyte-specific expression of a small subset of transcription factors (Egr1, HoxB7, STAT3), known abundant granulocyte proteins (e.g., S100A8, S100A9, neutrophil elastase), and specific receptors (fMLP, G-CSF). These findings suggested that appropriate stimuli might mediate rapid interconversion of the major myeloid cell types, for example, in inflammation. In keeping with this hypothesis, we showed that purified Ly-6G-positive granulocytes express CSF-1R after overnight culture and can subsequently differentiate to form F4/80-positive macrophages in response to CSF-1.

Human CD68 promoter GFP transgenic mice allow analysis of monocyte to macrophage differentiation in vivo

“…Flow cytometric phenotyping using antibodies directed against the CXCR2 and CXCR4 chemokine receptors showed that GFP expression by neutrophils in the blood of CD68-GFP mice may be able to inform of neutrophil subsets, with the newly mobilized CXCR4 LO neutrophils showing high GFP expression compared with GFP 2 CXCR4 expressing senescent neutrophil population 55 (supplemental Figure 4). Other "macrophagespecific" markers including Emr1 (F4/80) and Csf1r mRNA have also been found in murine neutrophil granulocytes, 56 supporting the view that the generation of a truly macrophage specific reporter may be unattainable (reviewed elsewhere 22 ). Given our less than complete understanding of myeloid differentiation programs in vitro and in vivo, it is interesting to speculate on the differences seen in human CD68 promoter-driven GFP transgene expression with CX 3 CR1 knock-in GFP expression.…”

A Novel Mouse Model of Inflammatory Bowel Disease Links Mammalian Target of Rapamycin-Dependent Hyperproliferation of Colonic Epithelium to Inflammation-Associated Tumorigenesis

“…14 We therefore tested the effect of the conditional inactivation of Stat3 flox genes in immune cells using Cre driven by the colony-stimulating factor-1 receptor promoter. 15,16 This inactivated Stat3 in both myeloid and lymphoid cells, including macrophages, lymphocytes, and granulocytes, which produced not only a dramatic inflammatory response of the intestine but also eventual malignant tumor formation at a frequency similar to that observed in human IBD patients. These phenotypes were completely dependent on the intestinal microflora.…”

“…15,16 An improved Cre (iCre) sequence, based on mammalian codon usage, 17 was used for the transgenic construct to maximize efficiency of target excision. After introduction into FVB embryos, one of three founder mice transmitted the transgene to its offspring, which were phenotypically normal.…”

Caspase-8 is activated by cathepsin D-initiating neutrophil apoptosis during the resolution of inflammation

“…Neutrophils were also isolated from wild-type, cathepsin B Ϫ / Ϫ , and cathepsin D Ϫ / Ϫ mice. Mature mouse bone marrow (obtained from femur and tibia of the hind legs) and blood neutrophils (obtained by cardiac puncture) were positively selected using anti -Gr-1 monoclonal antibody (Miltenyi Biotec), as previously described ( 54 ). The purity of the resulting mouse neutrophil populations was > 90% (bone marrow) and > 95% (blood), respectively.…”