The receptor for granulocyte-colony stimulating factor (G-CSF) is expressed in radial glia during development of the nervous system

Abstract

Background: Granulocyte colony-stimulating (G-CSF) factor is a well-known hematopoietic growth factor stimulating the proliferation and differentiation of myeloid progenitors. Recently, we uncovered that G-CSF acts also as a neuronal growth factor in the brain, which promotes adult neural precursor differentiation and enhances regeneration of the brain after insults. In adults, the receptor for G-CSF is predominantly expressed in neurons in many brain areas. We also described expression in neurogenic regions of the adult brain, such as the subventricular zone and the subgranular layer of the dentate gyrus. In addition, we found close co-localization of the G-CSF receptor and its ligand G-CSF. Here we have conducted a systematic expression analysis of G-CSF receptor and its ligand in the developing embryo.

Results: Outside the central nervous system (CNS) we found G-CSF receptor expression in blood vessels, muscles and their respective precursors and neurons. The expression of the G-CSF receptor in the developing CNS was most prominent in radial glia cells.

Conclusion: Our data imply that in addition to the function of G-CSF and its receptor in adult neurogenesis, this system also has a role in embryonic neurogenesis and nervous system development.

Figure 1

The G-CSF receptor is expressed in structures outside the brain throughout development of the rat embryo. The figure gives an overview of the G-CSF receptor expression pattern in the rat embryo. A E11 heart, B E12 intestine, C E12 kidney, D E12 somite, E E12 tongue, F E16 cerebral artery, G, H E16 cervical dorsal root ganglia, I, J E16 tongue, K, L E16 eye, M, N E19 kidney, O E19 intestine, (Immunohistochemical staining of 10 μm paraffin sections, scale bar 50 μm, drg: dorsal root ganglia, E: embryonic day)

Figure 2

Expression of G-CSF and its receptor on the RNA level. G-CSF receptor (A) and its ligand G-CSF (B) are present throughout murine embryonic development, which is demonstrated by RT-PCR. RT-PCR products of the following stages were loaded on the gels: E11, E12, E14, E16, E18 and P2. As positive controls for G-CSF and G-CSF receptor sequence-verified cDNA clones were used. The negative control consisted of water. RNA was prepared out of E11 and E12 whole embryonic mouse heads, for the other stages mouse brain was taken. Primers are located in the 3' part of the open reading frames with product lengths of 235 bp for G-CSF receptor and 360 bp for G-CSF. (Pos., positive PCR control (G-CSF or G-CSF receptor, respectively; neg., negative control)

Figure 3

G-CSF receptor is expressed in the embryonic nervous system. The expression shows characteristics of radial glia cells in terms of long processes and termination in end-feet. A E11 forebrain, B E12 spinal cord with dorsal root ganglion, axon root and muscle, C E14 hindbrain, D E16 spinal cord with dorsal root ganglion, E E19 spinal cord, F E19 spinal cord, G E19 hindbrain, H E21 olfactory bulb, I E21 diencephalon, (Immunohistochemical staining of 10 μm paraffin sections, scale bar = 50 μm, d: dorsal, E: embryonic day, v: ventral).

Figure 4

G-CSF receptor and Nestin co-localize in the nervous system of the E16 rat embryo. The G-CSF receptor staining is shown in red, the signal for Nestin green. On images A-C the staining was performed on cortex tissue, D-F diencephalon and G-I spinal cord tissue. C, F and I are merged images.(Immunofluorescent staining on 10 μm paraffin sections, scale bar 50 μm, E: embryonic day).