Identification of CCR2, flotillin, and gp49B genes as new G-CSF targets during neutrophilic differentiation

Granulocyte colony-stimulating factor (G-CSF) is a cytokine that stimulates myeloid progenitor cells to proliferate and differentiate into neutrophilic granulocytes. To identify genes induced by G-CSF during neutrophil differentiation, interleukin-3-dependent murine myeloid precursor FDC-P1 cells expressing the G-CSF receptor were stimulated with G-CSF, and the gene expression profile was characterized by DNA microarray analysis. In addition to known signal transducer and activator of transcription-3 target genes, such as suppressor of cytokine signaling-3 (SOCS3), JunB, and p19(INK4D), we newly identified several G-CSF targets, including genes for the CC chemokine receptor-2 (CCR2), raft proteins flotillin-1 and flotillin-2, and immunoglobulin-like receptor gp49B. Real-time, quantitative polymerase chain reaction analyses revealed that the expression of these genes was induced in various myeloid cell lines by G-CSF. Furthermore, when HoxA9-immortalized bone marrow progenitors were induced by G-CSF to differentiate into mature neutrophils, all of these genes were strongly activated. These genes could be categorized into three groups based on their time-course of expression: immediate-early (approximately 20 min, SOCS3), mid-early (2-4 h, flotillin-1/2 and gp49B), and late (>12 h, CCR2). This suggests that different transcriptional mechanisms are involved in the regulation of these genes. We show that bone marrow neutrophils express functional CCR2, which suggest that CC chemokines may play previously unknown roles in neutrophil activation and chemotaxis.