Evidence for Developmentally Regulated Local Translation of Odorant Receptor mRNAs in the Axons of Olfactory Sensory Neurons

Odorant receptor mRNAs are transported within axons of olfactory sensory neurons that project into the olfactory bulb. Odorant receptor proteins have been identified along the distal part of these axons, which raises the possibility of their local synthesis in axons. We took advantage of the anatomical separation between the olfactory mucosa (which contains the sensory neuron cell bodies) and the bulb (which contains sensory axons but no sensory neuron cell bodies) to address this issue using a quantitative biochemical approach. Combining a method that separates polysome-associated mRNAs from untranslated mRNAs with a reverse transcription–quantitative PCR approach, we demonstrate that significant amounts of odorant receptor mRNAs are associated with polysomes in the sensory axons of the adult mouse bulb. We thus provide the first evidence for local synthesis of odorant receptor proteins in these axons. Interestingly, the rate of odorant receptor mRNA translation in axons is significantly greater during periods when the proportion of immature axons is higher (i.e., at postnatal day 4 or on regeneration after chemical lesion in adults). In contrast, the olfactory marker protein mRNA, which is restricted to mature axons, is translated at a low and constant level. Overall, we demonstrate that translation levels of odorant receptor mRNAs in axons are developmentally regulated, and positively correlated to the stage of axonal growth into the bulb. Given the established function of odorant receptors in the axonal wiring of sensory projections, we propose that this regulated axonal translation may play a role in the development and maintenance of the glomerular array.

[1]  A. Giuditta,et al.  Local gene expression in axons and nerve endings: the glia-neuron unit. , 2008, Physiological reviews.

[2]  Jiaqi Yao,et al.  An essential role for β-actin mRNA localization and translation in Ca2+-dependent growth cone guidance , 2006, Nature Neuroscience.

[3]  R. Axel,et al.  Odorant Receptors on Axon Termini in the Brain , 2004, Science.

[4]  W. Sossin,et al.  Intracellular Trafficking of RNA in Neurons , 2006, Traffic.

[5]  A. Mackay-Sim,et al.  On the Life Span of Olfactory Receptor Neurons , 1991, The European journal of neuroscience.

[6]  H. Sakano,et al.  Olfactory Neurons Expressing Closely Linked and Homologous Odorant Receptor Genes Tend to Project Their Axons to Neighboring Glomeruli on the Olfactory Bulb , 1999, The Journal of Neuroscience.

[7]  Hitoshi Sakano,et al.  A Neuronal Identity Code for the Odorant Receptor-Specific and Activity-Dependent Axon Sorting , 2006, Cell.

[8]  H. Loh,et al.  Axonal mRNA transport and localized translational regulation of κ-opioid receptor in primary neurons of dorsal root ganglia , 2006, Proceedings of the National Academy of Sciences.

[9]  C. Holt,et al.  Local translation and directional steering in axons , 2007, The EMBO journal.

[10]  Hitoshi Sakano,et al.  Odorant Receptor–Derived cAMP Signals Direct Axonal Targeting , 2006, Science.

[11]  Paul C. Letourneau,et al.  Protein Synthesis in Distal Axons Is Not Required for Growth Cone Responses to Guidance Cues , 2009, The Journal of Neuroscience.

[12]  J. Kauer,et al.  Olfactory marker protein mRNA is found in axons of olfactory receptor neurons , 1995, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[13]  M. Morales,et al.  Aggregation of vasopressin mRNA in a subset of axonal swellings of the median eminence and posterior pituitary: light and electron microscopic evidence , 1994, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[14]  C. Holt,et al.  A functional equivalent of endoplasmic reticulum and Golgi in axons for secretion of locally synthesized proteins , 2009, Molecular and Cellular Neuroscience.

[15]  J. Flanagan,et al.  Axonal Protein Synthesis Provides a Mechanism for Localized Regulation at an Intermediate Target , 2002, Cell.

[16]  Richard Axel,et al.  Topographic organization of sensory projections to the olfactory bulb , 1994, Cell.

[17]  Linda B. Buck,et al.  Information coding in the olfactory system: Evidence for a stereotyped and highly organized epitope map in the olfactory bulb , 1994, Cell.

[18]  C. Greer,et al.  Postnatal development of olfactory receptor cell axonal arbors , 1998, The Journal of comparative neurology.

[19]  M. Zaccolo,et al.  Odorant receptors at the growth cone are coupled to localized cAMP and Ca2+ increases , 2009, Proceedings of the National Academy of Sciences.

[20]  A. Prochiantz,et al.  Emx2 homeodomain transcription factor interacts with eukaryotic translation initiation factor 4E (eIF4E) in the axons of olfactory sensory neurons. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[21]  Z. Peterlin,et al.  A G protein/cAMP signal cascade is required for axonal convergence into olfactory glomeruli , 2007, Proceedings of the National Academy of Sciences.

[22]  Konstantin A Lukyanov,et al.  Intra-axonal translation and retrograde trafficking of CREB promotes neuronal survival , 2008, Nature Cell Biology.

[23]  C. Holt,et al.  Chemotropic Responses of Retinal Growth Cones Mediated by Rapid Local Protein Synthesis and Degradation , 2001, Neuron.

[24]  Ivan Rodriguez,et al.  Axon Guidance of Mouse Olfactory Sensory Neurons by Odorant Receptors and the β2 Adrenergic Receptor , 2004, Cell.

[25]  Peter Mombaerts,et al.  Odorant receptor gene choice in olfactory sensory neurons: the one receptor–one neuron hypothesis revisited , 2004, Current Opinion in Neurobiology.

[26]  Peter Mombaerts,et al.  Axonal wiring in the mouse olfactory system. , 2006, Annual review of cell and developmental biology.

[27]  Evan Z. Macosko,et al.  Local translation of RhoA regulates growth cone collapse , 2005, Nature.

[28]  M. Kiebler,et al.  Neuronal RNA Granules: Movers and Makers , 2006, Neuron.

[29]  K. Mori,et al.  The olfactory bulb: coding and processing of odor molecule information. , 1999, Science.

[30]  A. Trembleau,et al.  Morphological and molecular features of the mammalian olfactory sensory neuron axons: What makes these axons so special? , 2005, Journal of neurocytology.

[31]  C. Greer,et al.  Glomerular formation in the developing rat olfactory bulb , 1999, The Journal of comparative neurology.

[32]  C. Holt,et al.  The transcription factor Engrailed-2 guides retinal axons , 2005, Nature.

[33]  Gordon M Shepherd,et al.  High-throughput microarray detection of olfactory receptor gene expression in the mouse. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[34]  C. Holt,et al.  Asymmetrical β-actin mRNA translation in growth cones mediates attractive turning to netrin-1 , 2006, Nature Neuroscience.

[35]  H. Breer,et al.  Olfactory Receptor Proteins in Axonal Processes of Chemosensory Neurons , 2004, The Journal of Neuroscience.

[36]  Peter Mombaerts,et al.  Specificity of Glomerular Targeting by Olfactory Sensory Axons , 2002, The Journal of Neuroscience.

[37]  J. Twiss,et al.  The evolving roles of axonally synthesized proteins in regeneration , 2006, Current Opinion in Neurobiology.

[38]  R. Axel,et al.  A novel multigene family may encode odorant receptors: A molecular basis for odor recognition , 1991, Cell.

[39]  L. Mannucci,et al.  Chemical Stimulation of Synaptosomes Modulates α-Ca2+/Calmodulin-Dependent Protein Kinase II mRNA Association to Polysomes , 2000, The Journal of Neuroscience.

[40]  D. Purves,et al.  Postnatal construction of neural circuitry in the mouse olfactory bulb , 1990, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[41]  Anthony E. Gioio,et al.  Axon Viability and Mitochondrial Function are Dependent on Local Protein Synthesis in Sympathetic Neurons , 2007, Cellular and Molecular Neurobiology.

[42]  L. Enquist,et al.  Olfactory Inputs to Hypothalamic Neurons Controlling Reproduction and Fertility , 2005, Cell.