The promoter of macrophage colony-stimulating factor receptor is active in astrocytes

Macrophage colony-stimulating factor (M-CSF) is a hematopoietin whose actions are essential for growth and survival of macrophages, placental development, ramification of microglia and tumor progression. The expression of the receptor for macrophage colony-stimulating factor (c-fms) is regulated by two distinct promoters: distal and proximal. The distal promoter is active in trophoblasts during embryogenesis and the proximal promoter directs expression to the cells of myeloid lineage. Here we report the generation of transgenic mice expressing beta-galactosidase under the control of the human proximal c-fms promoter and demonstrate the promoter activity in astrocytes, cells of neurological origin that partially take over the role of macrophages in the central nervous system. Enzymatic activity of beta-galactosidase was detected in homogenated spleen, bone marrow and brain and in the cell extracts from peritoneal macrophages of transgenic mice. Immunohistochemical staining of brain showed the presence of beta-galactosidase in astrocytes. We hypothesize that M-CSF released by astrocytes, upon stimulation by lipopolysaccharide (LPS), tumor necrosis factor alpha (TNF alpha) or interleukin-1 (IL-1), regulates the expression of its own receptor. (C) 1997 Elsevier Science Ireland Ltd.