Neuroscience, 120, Issue 1 , 4 August 2003, Pages 99-112
E. Asan (a), T. Langenhan (a), B. Holtmann (b), H. Bock (c), M. Sendtner (b) and P. Carroll (d)
(a) Institute for Anatomy and Cell Biology, University of Wuerzburg, Koellikerstrasse 6, 97070, Wuerzburg, Germany
(b) Institute of Clinical Neurobiology, University of Wuerzburg, Josef-Schneider-Strasse 11, 97080, Wuerzburg, Germany
(c) Department of Molecular Genetics, Southwestern Medical Center, Dallas, TX 75390-9046, USA
(d) INSERM U 432, Neurobiologie et Développement du Système Vestibulaire, Université Montpellier II, Place Eugène Bataillon, 34095, Montpellier cedex 05, France
Accepted 4 March 2003; Available online 25 June 2003 .
Ciliary neurotrophic factor (CNTF) is primarily regarded as an astrocytic lesion factor, promoting neuronal survival and influencing plasticity processes in deafferented areas of the CNS. Postnatal loss of neurons in CNTF-deficient mice indicates a function of the factor also under physiological conditions. In the olfactory bulb, where neurogenesis, axo- and synaptogenesis continue throughout life, CNTF content is constitutively high. The cellular localization of CNTF in the rat olfactory bulb is not fully resolved, and species differences between mouse and rat are not yet characterized. In the present study, four different CNTF antibodies and double immunolabeling with specific markers for glial and neuronal cells were used to study the cellular localization of CNTF in rat and mouse olfactory bulb. Specificity of the detection was checked with tissue from CNTF-deficient mice, and investigations were complemented by immunolocalization of reporter protein in mice synthesizing -galactosidase under control of the CNTF promoter (CNTF lacZ-knock-in mice). In both species, CNTF localized to ensheathing cell nuclei, cell bodies and axon-enveloping processes. Additionally, individual axons of olfactory neurons were CNTF immunoreactive. Both CNTF protein content and immunoreaction intensity were lower in mice than in rats. Scattered lightly CNTF-reactive cells were found in the granular and external plexiform layers in rats. Some CNTF-positive cells were associated with immunoreactivity for the polysialylated form of the neural cell adhesion molecule, which is expressed by maturing interneurons derived from the rostral migratory stream. In CNTF lacZ-knock-in mice, -galactosidase reactivity was found in ensheathing cells of the olfactory nerve layer, and in cells of the glomerular, external plexiform and granular layers. The study proves that CNTF is localized in glial and neuronal structures in the rodent olfactory bulb. Results in mice provide a basis for investigations concerning the effects of a lack of the factor in CNTF-deficient mice.
Author Keywords: ensheathing cells; olfactory neurons; neurogenesis; immunocytochemistry; glial fibrillary acidic protein; neural cell adhesion molecule
Abbreviations: a-CNTFm, monoclonal mouse-anti-rat ciliary neurotrophic factor; BDNF, brain-derived neurotrophic factor; CNTF, ciliary neurotrophic factor; CNTFR, ciliary neurotrophic factor receptor ; DAB, 3-3¢-diaminobenzidine; FGF2, basic fibroblast growth factor; GA, glutaraldehyde; ga-CNTFp, polyclonal goat-anti-ciliary neurotrophic factor; GFAP, glial fibrillary acidic protein; GOD, glucose oxidase; ir, immunoreactive; NCAM, neuronal cell adhesion molecule; NDS, normal donkey serum; NGS, normal goat serum; NiDAB, nickel-intensified 3-3¢-diaminobenzidine; NLS, nuclear localization signal; OMP, olfactory marker protein; ON, olfactory neuron; PBS, phosphate-buffered saline; PFA, paraformaldehyde; PSA, polysialylated; ra-CNTFp, polyclonal rabbit-anti-rat ciliary neurotrophic factor
Corresponding author. Tel: +49-931-312-715; fax: +49-931-312-712.