title: Deletion of voltage-gated channel affects glomerular refinement and odorant receptor expression in the mouse olfactory system.
abstract: Olfactory sensory neurons (OSNs) expressing a specific odorant receptor (OR) gene send axonal projections to specific glomeruli, creating a stereotypic olfactory sensory map. Odorant receptor sequence, G-protein cAMP signaling, and axon guidance molecules have been shown to direct axons of OSNs toward central targets in the olfactory bulb (OB). Although the OR sequence may act as one determinant, our objective was to elucidate the extent by which voltage-dependent activity of postsynaptic projection neurons in the OB centrally influences peripheral development and target destination of OSNs. We bred OR-tagged transgenic mice to homozygosity with mice that had a gene-targeted deletion of the Shaker potassium ion channel (Kv1.3) to elucidate how activity modulates synaptic connections that formulate the sensory map. Here we report that the Kv1.3 ion channel, which is predominantly expressed in mitral cells and whose gene-targeted deletion causes a "super-smeller" phenotype, alters synaptic refinement of axonal projections from OSNs expressing P2, M72, and MOR28 ORs. Absence of Kv1.3 voltage-gated activity caused the formation of small, heterogeneous, and supernumerary glomeruli that failed to undergo neural pruning over development. These changes were accompanied by a significant decrease in the number of P2-, M72-, and MOR28-expressing OSNs, which contained an overexpression of OR protein and G-protein G(olf) in the cilia of the olfactory epithelium. These findings suggest that voltage-gated activity of projection neurons is essential to refine primary olfactory projections and that it regulates proper expression of the transduction machinery at the periphery.
authors.affiliation: Department of Biological Science, Program in Neuroscience, Biomedical Research Facility, The Florida State University, Tallahassee, Florida 32306, USA.
authors.forename: K C
authors.initials: KC
authors.lastname: Biju
authors.forename: David Ronald
authors.initials: DR
authors.lastname: Marks
authors.forename: Thomas Gerald
authors.initials: TG
authors.lastname: Mast
authors.forename: Debra Ann
authors.initials: DA
authors.lastname: Fadool
mesh_terms: D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000502:physiology / Q000648:ultrastructure; D019204:GTP-Binding Proteins / Q000378:metabolism; D005697:Galactosides / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007211:Indoles / Q000378:metabolism; D051664:Kv1.3 Potassium Channel / Q000172:deficiency* / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D008855:Microscopy, Electron, Scanning / Q000379:methods; D009154:Mutation; D009475:Neurons, Afferent / Q000166:cytology* / Q000378:metabolism* / Q000648:ultrastructure; D051842:Olfactory Marker Protein / Q000378:metabolism; D009833:Olfactory Pathways / Q000166:cytology* / Q000378:metabolism; D018035:Receptors, Odorant / Q000235:genetics / Q000378:metabolism*
chemical_list: D005697:Galactosides; D007211:Indoles; D051664:Kv1.3 Potassium Channel; D051842:Olfactory Marker Protein; D018035:Receptors, Odorant; D049452:Green Fluorescent Proteins; D019204:GTP-Binding Proteins; C044888:5-bromo-4-chloro-3-indolyl beta-galactoside