Expression of Gal4-dependent transgenes in cells of the mononuclear phagocyte system labeled with enhanced cyan fluorescent protein usingCsf1r-Gal4VP16/UAS-ECFP double-transgenic mice

Abstract

We generated double-transgenic mice carrying cointegrated tissue-specific Gal4 and Gal4 reporter transgenes to direct transgene overexpression in the mononuclear phagocyte system (MPS). A modified promoter of the Csf1r (c-fms) gene, containing a deletion of the trophoblast-specific promoter, was used to drive the expression of Gal4VP16 transcriptional activator specifically in macrophages. This module was cointegrated with a fluorescent reporter, enhanced cyan fluorescent protein (ECFP), driven by a Gal4-dependent promoter. ECFP fluorescence was first detected in forming blood islands of the yolk sac at 8 dpc, then in macrophages in the yolk sac and the embryo proper. In adult mice ECFP was detected primarily in monocytes, tissue macrophages, microglia, and dendritic cells, including Langerhans cells of the skin. Crossing of these mice to transgenics containing tagged protein under control of a Gal4-dependent promoter directed expression of that protein in mononuclear phagocytes of double-transgenic animals. The new mouse line provides a useful tool for overexpression of transgenes in cells of the myeloid lineage, while simultaneously labeling them by ECFP expression.

Macrophages and CSF-1

“…18 The first true embryonic macrophages are evident from E8 and are derived from the primitive endoderm of the yolk sac. 18,20 From E8-9, macrophages are cell death such as the interdigital webbing during embryogenesis, 20 and inactivation of the apoptotic gene psr results in perturbed development of the lungs, brain and eye due to excessive tissue and impaired cellular clearance. 32 Macrophages also contribute to the induction of programmed cell death with macrophage-derived signaling directing apoptosis as part of the regulation of tissue morphogenesis.…”

“…49,52 They also produce cytotoxic mediators including oxidative and nitrogen evident throughout the yolk sac and begin to invade the embryo proper migrating into the developing head. 18,20 Definitive hematopoiesis, defined as the derivation of hemopoietic cells from multipotent hemopoietic stem cells (HSCs), begins at approximately E10.5 from progenitors originating in the aortogonado-mesonephron (AGM) region. 21,22 From E12 onwards, the liver is primary site of myeloid production.…”

“…4,19,28,60 CSF-1R is one of the earliest markers of these cells indicating the importance of CSF-1 in the differentiation and propagation of macrophages from the earliest stages of development. 20,83 Indeed, it is the early and consistent expression of the CSF-1R that has provided an important tool for tracking developmental macrophages. 20,83 The absence of CSF-1 results in a range of developmental abnormalities, including skeletal, neurological, growth and fertility defects, [25][26][27][28] primarily stemming from the severe deficiency in tissue macrophages.…”

“…20,83 Indeed, it is the early and consistent expression of the CSF-1R that has provided an important tool for tracking developmental macrophages. 20,83 The absence of CSF-1 results in a range of developmental abnormalities, including skeletal, neurological, growth and fertility defects, [25][26][27][28] primarily stemming from the severe deficiency in tissue macrophages. Interestingly while these developmental defects are striking, CSF-1-deficient mice (Csf1 op/op ) exhibit few immunological defects.…”

“…Virtually all organs contain a resident population, comprising up to 15%, which reside independent of inflammatory or immune stimulus. 20,83 The is associated with pregnancy loss 126 and women with reduced circulating CSF-1 have a higher rate of recurrent spontaneous abortion. 127 CSF-1 also mediates reproductive function through macrophage regulation.…”