Prion Protein (PrP c ) Immunocytochemistry and Expression of the Green Fluorescent Protein Reporter Gene under Control of the Bovine PrP Gene Promoter in the Mouse Brain YANNICK BAILLY, 1 * ANNE-MARIE HAEBERLE ´ , 1 FRANC ¸ OISE BLANQUET-GROSSARD, 2 SYLVETTE CHASSEROT-GOLAZ, 1 NANCY GRANT, 1 TOBIAS SCHULZE, 2 GUY BOMBARDE, 1 JACQUES GRASSI, 3 JEAN-YVES CESBRON, 2 AND CATHERINE LEMAIRE-VIEILLE 2 1 Neurotransmission et Se ´cre ´tion Neuroendocrine UPR 2356 Centre National de la Recherche Scientifique, IFR37 des Neurosciences, 67084 Strasbourg, France 2 Laboratoire de Physiopathologie des Ence ´phalopathies Spongiformes Transmissibles, U167 Institut National de la Sante ´ et de la Recherche Me ´dicale Institut de Biologie de Lille, Institut Pasteur de Lille, BP 447, 59800 Lille cedex, France 3 Service de Pharmacologie et d’Immunologie CEA-Saclay, 91191 Gif–sur–Yvette, France ABSTRACT Expression of the cellular prion protein (PrP c ) by host cells is required for prion replication and neuroinvasion in transmissible spongiform encephalopathies. As a consequence, identifica- tion of the cell types expressing PrP c is necessary to determine the target cells involved in the cerebral propagation of prion diseases. To identify the cells expressing PrP c in the mouse brain, the immunocytochemical localization of PrP c was investigated at the cellular and ultrastructural levels in several brain regions. In addition, we analyzed the expression pattern of a green fluorescent protein reporter gene under the control of regulatory sequences of the bovine prion protein gene in the brain of transgenic mice. By using a preembedding immunogold technique, neuronal PrP c was observed mainly bound to the cell surface and presynaptic sites. Dictyosomes and recycling organelles in most of the major neuron types also exhibited PrP c antigen. In the olfactory bulb, neocortex, putamen, hippocampus, thalamus, and cerebellum, the distribution pattern of both green fluorescent protein and PrP c immunoreactivity suggested that the trans- genic regulatory sequences of the bovine PrP gene were sufficient to promote expression of the reporter gene in neurons that express immunodetectable endogenous PrP c . Transgenic mice expressing PrP-GFP may thus provide attractive murine models for analyzing the transcrip- tional activity of the Prnp gene during prion infections as well as the anatomopathological kinetics of prion diseases. J. Comp. Neurol. 473:244 –269, 2004. © 2004 Wiley-Liss, Inc. Indexing terms: immunogold; electron microscopy; histofluorescence; transgenic mouse; central nervous system Franc ¸oise Blanquet-Grossard’s, Jean-Yves Cesbron’s, and Catherine Lemaire-Vieille’s current address is Transmission et Pathogene ` se des Mal- adies a ` Prion, CNRS FRE 2685, Universite ´ Joseph Fourier BP185, 38042 Grenoble cedex, France. Grant sponsor: Centre National de la Recherche Scientifique; Grant sponsor: Ministe `re de la Recherche et de la Technologie “Programme de Recherche sur les ESST et les Prions”—Action Concerte ´e No. 1 (Y.B., J.-Y.C); Grant sponsor: Programme de Recherche en Re ´seau; Grant spon- sor: the Economic European Community—Food Agro-Industry Research; Grant number: JCT 6022 (J.-Y.C.). *Correspondence to: Yannick J. Bailly, Neurotransmission et Se ´cre ´tion Neuroendocrine UPR 2356 CNRS, Centre de Neurochimie, 5 rue Blaise Pascal, 67084 Strasbourg, France. E-mail: byan@neurochem.u-strasbg.fr Received 12 August 2003; Revised 11 December 2003; Accepted 6 Janu- ary 2004 DOI 10.1002/cne.20117 Published online in Wiley InterScience (www.interscience.wiley.com). THE JOURNAL OF COMPARATIVE NEUROLOGY 473:244 –269 (2004) © 2004 WILEY-LISS, INC.