title: Growth factor-induced c-fos expression defines distinct subsets of midbrain dopaminergic neurons.
abstract: Growth factors are considered pivotal for the development, maintenance, and function of mesencephalic dopaminergic neurons. Recent studies have identified a plethora of growth factors which support the survival and differentiation of embryonic dopaminergic neurons. However, the exact cellular targets of these growth factors, and, thus, their precise mechanisms of action, remain largely unknown. To identify these cellular targets, we analysed, at the single cell level, growth factor-induced c-fos expression in dissociated mesencephalic cell cultures derived from a fos-lac Z transgenic mouse line. Pharmacological interference with cell-cell communication was utilized to control for direct growth factor effects. beta-Galactosidase-expressing cells were phenotypically characterized by immunocytochemistry to specific neural cell markers. Glia cell line-derived neurotrophic factor, basic fibroblast growth factor, brain-derived neurotrophic factor, and neurotrophin-3 directly induced Fos expression in differently sized, yet overlapping, populations of tyrosine hydroxylase-immunoreactive dopaminergic neurons. In an additional subpopulation of dopaminergic neurons, neurotrophin-3 induced fos-lac Z expression indirectly through a glutamate-mediated activation of N-methyl-D-aspartate receptors. Consistent with their proposed glial-mediated mode of action, transforming growth factor alpha and platelet-derived growth factor induced Fos expression predominantly in glia but only in a very small number of dopaminergic neurons. These findings demonstrate that individual dopaminergic neurons represent the direct targets of different sets of extracellular growth factors. Our findings further establish that growth factors affect dopaminergic neurons by indirect mechanisms which require specific cell-cell communication. These data also suggest a potential role for growth factors in the establishment of the morphological and functional diversity of midbrain dopaminergic neurons.
authors.affiliation: Universität Ulm, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Engele
authors.forename: K
authors.initials: K
authors.lastname: Schilling
mesh_terms: D000818:Animals; D000077214:Becaplermin; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology; D003433:Crosses, Genetic; D004298:Dopamine / Q000378:metabolism*; D005260:Female; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects*; D017930:Genes, Reporter; D016762:Genes, fos; D005838:Genotype; D051100:Glial Cell Line-Derived Neurotrophic Factor; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis; D006133:Growth Substances / Q000494:pharmacology*; D007763:Lac Operon; D008297:Male; D008636:Mesencephalon / Q000166:cytology / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008869:Microtubule-Associated Proteins / Q000032:analysis; D009414:Nerve Growth Factors / Q000494:pharmacology*; D009419:Nerve Tissue Proteins / Q000494:pharmacology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D020933:Neurotrophin 3; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis*; D020574:Proto-Oncogene Proteins c-sis; D011995:Recombination, Genetic; D016211:Transforming Growth Factor alpha / Q000494:pharmacology; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism; D001616:beta-Galactosidase / Q000032:analysis / Q000096:biosynthesis
chemical_list: D019208:Brain-Derived Neurotrophic Factor; C495040:Gdnf protein, mouse; D051100:Glial Cell Line-Derived Neurotrophic Factor; D005904:Glial Fibrillary Acidic Protein; D006133:Growth Substances; D008869:Microtubule-Associated Proteins; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D020933:Neurotrophin 3; D010982:Platelet-Derived Growth Factor; D016760:Proto-Oncogene Proteins c-fos; D020574:Proto-Oncogene Proteins c-sis; D016211:Transforming Growth Factor alpha; D016222:Fibroblast Growth Factor 2; D000077214:Becaplermin; D014446:Tyrosine 3-Monooxygenase; D001616:beta-Galactosidase; D004298:Dopamine