1
|
Hirata T. Olfactory information processing viewed through mitral and tufted cell-specific channels. Front Neural Circuits 2024; 18:1382626. [PMID: 38523698 PMCID: PMC10957668 DOI: 10.3389/fncir.2024.1382626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Accepted: 02/29/2024] [Indexed: 03/26/2024] Open
Abstract
Parallel processing is a fundamental strategy of sensory coding. Through this processing, unique and distinct features of sensations are computed and projected to the central targets. This review proposes that mitral and tufted cells, which are the second-order projection neurons in the olfactory bulb, contribute to parallel processing within the olfactory system. Based on anatomical and functional evidence, I discuss potential features that could be conveyed through the unique channel formed by these neurons.
Collapse
Affiliation(s)
- Tatsumi Hirata
- Brain Function Laboratory, National Institute of Genetics, SOKENDAI, Mishima, Japan
| |
Collapse
|
2
|
Dang P, Barnes DT, Cheng RP, Xu A, Moon YJ, Kodukula SS, Raper JA. Netrins and Netrin Receptors are Essential for Normal Targeting of Sensory Axons in the Zebrafish Olfactory Bulb. Neuroscience 2023; 508:19-29. [PMID: 35940453 PMCID: PMC9839495 DOI: 10.1016/j.neuroscience.2022.08.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 07/29/2022] [Accepted: 08/01/2022] [Indexed: 01/17/2023]
Abstract
Olfactory sensory neurons that express related odorant receptors specifically target large identifiable neuropils called protoglomeruli when they first reach the olfactory bulb in the zebrafish. This crude odorant receptor-related mapping is further refined as odorant receptor-specific glomeruli segregate from protoglomeruli later in development. Netrins are a prominent class of axon guidance molecules whose contribution to olfactory circuit formation is poorly studied. Morpholino knock down experiments have suggested that Netrin/Dcc signaling is involved in normal protoglomerular targeting. Here we extend these findings with more detailed characterization and modeling of netrin expression, and by examining protoglomerular targeting in mutant lines fornetrin1a (ntn1a), netrin1b (ntn1b), and their receptorsunc5b,dcc, andneo1a. We confirm thatntn1a,ntn1b, anddccare required for normal protoglomerular guidance of a subset of olfactory sensory neurons that are labeled with the Tg(or111-7:IRES:Gal4) transgene. We also observe errors in the targeting of these axons inunc5bmutants, but not inneo1a mutants. Our findings are consistent with ntn1a andntn1bacting primarily as attractants for olfactory sensory neurons targeting the central zone protoglomerulus.
Collapse
Affiliation(s)
- Puneet Dang
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | - Daniel T Barnes
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA; Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Ryan P Cheng
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | - Alison Xu
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | - Yoon Ji Moon
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | - Sai Sripad Kodukula
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | - Jonathan A Raper
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
| |
Collapse
|
3
|
Martončíková M, Alexovič Matiašová A, Ševc J, Račeková E. Relationship between Blood Vessels and Migration of Neuroblasts in the Olfactory Neurogenic Region of the Rodent Brain. Int J Mol Sci 2021; 22:11506. [PMID: 34768936 PMCID: PMC8583928 DOI: 10.3390/ijms222111506] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 10/18/2021] [Accepted: 10/20/2021] [Indexed: 11/25/2022] Open
Abstract
Neural precursors originating in the subventricular zone (SVZ), the largest neurogenic region of the adult brain, migrate several millimeters along a restricted migratory pathway, the rostral migratory stream (RMS), toward the olfactory bulb (OB), where they differentiate into interneurons and integrate into the local neuronal circuits. Migration of SVZ-derived neuroblasts in the adult brain differs in many aspects from that in the embryonic period. Unlike in that period, postnatally-generated neuroblasts in the SVZ are able to divide during migration along the RMS, as well as they migrate independently of radial glia. The homophilic mode of migration, i.e., using each other to move, is typical for neuroblast movement in the RMS. In addition, it has recently been demonstrated that specifically-arranged blood vessels navigate SVZ-derived neuroblasts to the OB and provide signals which promote migration. Here we review the development of vasculature in the presumptive neurogenic region of the rodent brain during the embryonic period as well as the development of the vascular scaffold guiding neuroblast migration in the postnatal period, and the significance of blood vessel reorganization during the early postnatal period for proper migration of RMS neuroblasts in adulthood.
Collapse
Affiliation(s)
- Marcela Martončíková
- Department of Regenerative Medicine and Cell Therapy, Institute of Neurobiology, Biomedical Research Center, Slovak Academy of Sciences, Šoltésovej 4, 040 01 Košice, Slovakia;
| | - Anna Alexovič Matiašová
- Department of Cell Biology, Institute of Biology and Ecology, Faculty of Science, Pavol Jozef Šafárik University in Košice, Šrobárova 2, 041 54 Košice, Slovakia; (A.A.M.); (J.Š.)
| | - Juraj Ševc
- Department of Cell Biology, Institute of Biology and Ecology, Faculty of Science, Pavol Jozef Šafárik University in Košice, Šrobárova 2, 041 54 Košice, Slovakia; (A.A.M.); (J.Š.)
| | - Enikő Račeková
- Department of Regenerative Medicine and Cell Therapy, Institute of Neurobiology, Biomedical Research Center, Slovak Academy of Sciences, Šoltésovej 4, 040 01 Košice, Slovakia;
| |
Collapse
|
4
|
Hirata T, Tohsato Y, Itoga H, Shioi G, Kiyonari H, Oka S, Fujimori T, Onami S. NeuroGT: A brain atlas of neurogenic tagging CreER drivers for birthdate-based classification and manipulation of mouse neurons. CELL REPORTS METHODS 2021; 1:100012. [PMID: 35474959 PMCID: PMC9017123 DOI: 10.1016/j.crmeth.2021.100012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 04/02/2021] [Accepted: 04/23/2021] [Indexed: 11/30/2022]
Abstract
Neuronal birthdate is one of the major determinants of neuronal phenotypes. However, most birthdating methods are retrospective in nature, allowing very little experimental access to the classified neuronal subsets. Here, we introduce four neurogenic tagging mouse lines, which can assign CreER-loxP recombination to neuron subsets that share the same differentiation timing in living animals and enable various experimental manipulations of the classified subsets. We constructed a brain atlas of the neurogenic tagging mouse lines (NeuroGT), which includes holistic image data of the loxP-recombined neurons and their processes across the entire brain that were tagged on each single day during the neurodevelopmental period. This image database, which is open to the public, offers investigators the opportunity to find specific neurogenic tagging driver lines and the stages of tagging appropriate for their own research purposes.
Collapse
Affiliation(s)
- Tatsumi Hirata
- Brain Function Laboratory, National Institute of Genetics, 1111 Yata, Mishima 411-8540, Japan
- The Graduate University for Advanced Studies, SOKENDAI, Hayama, Japan
| | - Yukako Tohsato
- Computational Biology Laboratory, Faculty of Information Science and Engineering, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga 525-8577, Japan
- Laboratory for Developmental Dynamics, RIKEN Center for Biosystems Dynamics Research, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe 650-0047, Japan
| | - Hiroya Itoga
- Laboratory for Developmental Dynamics, RIKEN Center for Biosystems Dynamics Research, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe 650-0047, Japan
| | - Go Shioi
- Laboratory for Animal Resources and Genetic Engineering, RIKEN Center for Biosystems Dynamics Research, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe 650-0047, Japan
| | - Hiroshi Kiyonari
- Laboratory for Animal Resources and Genetic Engineering, RIKEN Center for Biosystems Dynamics Research, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe 650-0047, Japan
| | - Sanae Oka
- Division of Embryology, National Institute for Basic Biology, 5-1 Higashiyama, Myodaiji, Okazaki 444-8787, Japan
| | - Toshihiko Fujimori
- The Graduate University for Advanced Studies, SOKENDAI, Hayama, Japan
- Division of Embryology, National Institute for Basic Biology, 5-1 Higashiyama, Myodaiji, Okazaki 444-8787, Japan
| | - Shuichi Onami
- Laboratory for Developmental Dynamics, RIKEN Center for Biosystems Dynamics Research, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe 650-0047, Japan
- Life Science Data Sharing Unit, RIKEN Information R&D and Strategy Headquarters, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe 650-0047, Japan
| |
Collapse
|
5
|
Imamura F, Ito A, LaFever BJ. Subpopulations of Projection Neurons in the Olfactory Bulb. Front Neural Circuits 2020; 14:561822. [PMID: 32982699 PMCID: PMC7485133 DOI: 10.3389/fncir.2020.561822] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 08/12/2020] [Indexed: 12/17/2022] Open
Abstract
Generation of neuronal diversity is a biological strategy widely used in the brain to process complex information. The olfactory bulb is the first relay station of olfactory information in the vertebrate central nervous system. In the olfactory bulb, axons of the olfactory sensory neurons form synapses with dendrites of projection neurons that transmit the olfactory information to the olfactory cortex. Historically, the olfactory bulb projection neurons have been classified into two populations, mitral cells and tufted cells. The somata of these cells are distinctly segregated within the layers of the olfactory bulb; the mitral cells are located in the mitral cell layer while the tufted cells are found in the external plexiform layer. Although mitral and tufted cells share many morphological, biophysical, and molecular characteristics, they differ in soma size, projection patterns of their dendrites and axons, and odor responses. In addition, tufted cells are further subclassified based on the relative depth of their somata location in the external plexiform layer. Evidence suggests that different types of tufted cells have distinct cellular properties and play different roles in olfactory information processing. Therefore, mitral and different types of tufted cells are considered as starting points for parallel pathways of olfactory information processing in the brain. Moreover, recent studies suggest that mitral cells also consist of heterogeneous subpopulations with different cellular properties despite the fact that the mitral cell layer is a single-cell layer. In this review, we first compare the morphology of projection neurons in the olfactory bulb of different vertebrate species. Next, we explore the similarities and differences among subpopulations of projection neurons in the rodent olfactory bulb. We also discuss the timing of neurogenesis as a factor for the generation of projection neuron heterogeneity in the olfactory bulb. Knowledge about the subpopulations of olfactory bulb projection neurons will contribute to a better understanding of the complex olfactory information processing in higher brain regions.
Collapse
Affiliation(s)
- Fumiaki Imamura
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA, United States
| | - Ayako Ito
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA, United States
| | - Brandon J LaFever
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA, United States
| |
Collapse
|
6
|
Lane G, Zhou G, Noto T, Zelano C. Assessment of direct knowledge of the human olfactory system. Exp Neurol 2020; 329:113304. [PMID: 32278646 DOI: 10.1016/j.expneurol.2020.113304] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Revised: 01/13/2020] [Accepted: 04/08/2020] [Indexed: 12/31/2022]
Affiliation(s)
- Gregory Lane
- Northwestern University Feinberg School of Medicine, Department of Neurology, 303 E Chicago Ave, Chicago, IL 60611, USA.
| | - Guangyu Zhou
- Northwestern University Feinberg School of Medicine, Department of Neurology, 303 E Chicago Ave, Chicago, IL 60611, USA.
| | - Torben Noto
- Northwestern University Feinberg School of Medicine, Department of Neurology, 303 E Chicago Ave, Chicago, IL 60611, USA
| | - Christina Zelano
- Northwestern University Feinberg School of Medicine, Department of Neurology, 303 E Chicago Ave, Chicago, IL 60611, USA
| |
Collapse
|
7
|
Hirata T, Shioi G, Abe T, Kiyonari H, Kato S, Kobayashi K, Mori K, Kawasaki T. A Novel Birthdate-Labeling Method Reveals Segregated Parallel Projections of Mitral and External Tufted Cells in the Main Olfactory System. eNeuro 2019; 6:ENEURO.0234-19.2019. [PMID: 31672846 PMCID: PMC6868177 DOI: 10.1523/eneuro.0234-19.2019] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 10/16/2019] [Accepted: 10/19/2019] [Indexed: 01/09/2023] Open
Abstract
A fundamental strategy in sensory coding is parallel processing, whereby unique, distinct features of sensation are computed and projected to the central target in the form of submodal maps. It remains unclear, however, whether such parallel processing strategy is employed in the main olfactory system, which codes the complex hierarchical odor and behavioral scenes. A potential scheme is that distinct subsets of projection neurons in the olfactory bulb (OB) form parallel projections to the targets. Taking advantage of the observation that the distinct projection neurons develop at different times, we developed a Cre-loxP-based method that allows for birthdate-specific labeling of cell bodies and their axon projections in mice. This birthdate tag analysis revealed that the mitral cells (MCs) born in an early developmental stage and the external tufted cells (TCs) born a few days later form segregated parallel projections. Specifically, the latter subset converges the axons onto only two small specific targets, one of which, located at the anterolateral edge of the olfactory tubercle (OT), excludes widespread MC projections. This target is made up of neurons that express dopamine D1 but not D2 receptor and corresponds to the most anterolateral isolation of the CAP compartments (aiCAP) that were defined previously. This finding of segregated projections suggests that olfactory sensing does indeed involve parallel processing of functionally distinct submodalities. Importantly, the birthdate tag method used here may pave the way for deciphering the functional meaning of these individual projection pathways in the future.
Collapse
Affiliation(s)
- Tatsumi Hirata
- Brain Function Laboratory, National Institute of Genetics
- Graduate University for Advanced Studies, SOKENDAI, Mishima 411-8540, Japan
| | - Go Shioi
- Laboratory for Genetic Engineering, RIKEN Center for Biosystems Dynamics Research, Kobe 650-0047, Japan
| | - Takaya Abe
- Laboratory for Genetic Engineering, RIKEN Center for Biosystems Dynamics Research, Kobe 650-0047, Japan
- Laboratory for Animal Resource Development, RIKEN Center for Biosystems Dynamics Research, Kobe 650-0047, Japan
| | - Hiroshi Kiyonari
- Laboratory for Genetic Engineering, RIKEN Center for Biosystems Dynamics Research, Kobe 650-0047, Japan
- Laboratory for Animal Resource Development, RIKEN Center for Biosystems Dynamics Research, Kobe 650-0047, Japan
| | - Shigeki Kato
- Department of Molecular Genetics, Institute of Biomedical Sciences, Fukushima Medical University School of Medicine, Fukushima 960-1295, Japan
| | - Kazuto Kobayashi
- Department of Molecular Genetics, Institute of Biomedical Sciences, Fukushima Medical University School of Medicine, Fukushima 960-1295, Japan
| | - Kensaku Mori
- Department of Physiology, Graduate School of Medicine, the University of Tokyo, Tokyo 113-0033, Japan
| | - Takahiko Kawasaki
- Brain Function Laboratory, National Institute of Genetics
- Graduate University for Advanced Studies, SOKENDAI, Mishima 411-8540, Japan
| |
Collapse
|
8
|
Bellesi M, Haswell JD, de Vivo L, Marshall W, Roseboom PH, Tononi G, Cirelli C. Myelin modifications after chronic sleep loss in adolescent mice. Sleep 2019; 41:4850494. [PMID: 29741724 DOI: 10.1093/sleep/zsy034] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Indexed: 01/28/2023] Open
Abstract
Study Objectives Previous studies found that sleep loss can suppress the expression of genes implicated in myelination and can have adverse effects on oligodendrocyte precursor cells. On the other hand, sleep may favor myelination by promoting the expression of genes involved in its formation and maintenance. Albeit limited, these results suggest that sleep loss can have detrimental effects on the formation and maintenance of myelin. Methods Here, we tested this hypothesis by evaluating ultrastructural modifications of myelin in two brain regions (corpus callosum and lateral olfactory tract) of mice exposed to different periods of sleep loss, from a few hours of sleep deprivation to ~5 days of chronic sleep restriction. In addition, we measured the internodal length-the distance between consecutive nodes of Ranvier along the axon-and plasma corticosterone levels. Results We find that g-ratio-the ratio of the diameter of the axon itself to the outer diameter of the myelinated fiber-increases after chronic sleep loss. This effect is mediated by a reduction in myelin thickness and is not associated with changes in the internodal length. Relative to sleep, plasma corticosterone levels increase after acute sleep deprivation, but show only a trend to increase after chronic sleep loss. Conclusions Chronic sleep loss may negatively affect myelin.
Collapse
Affiliation(s)
- Michele Bellesi
- Department of Psychiatry, University of Wisconsin-Madison, Madison, WI.,Department of Experimental and Clinical Medicine, Section of Neuroscience and Cell Biology, Università Politecnica delle Marche, Ancona, Italy
| | | | - Luisa de Vivo
- Department of Psychiatry, University of Wisconsin-Madison, Madison, WI
| | - William Marshall
- Department of Psychiatry, University of Wisconsin-Madison, Madison, WI
| | | | - Giulio Tononi
- Department of Psychiatry, University of Wisconsin-Madison, Madison, WI
| | - Chiara Cirelli
- Department of Psychiatry, University of Wisconsin-Madison, Madison, WI
| |
Collapse
|
9
|
Hirata T, Iwai L. Timing matters: A strategy for neurons to make diverse connections. Neurosci Res 2018; 138:79-83. [PMID: 30227163 DOI: 10.1016/j.neures.2018.09.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Revised: 08/21/2018] [Accepted: 08/21/2018] [Indexed: 11/18/2022]
Abstract
Neurogenesis proceeds like a continuous wave, in which each type of neurons is produced over a few days to several days. During this protracted time window, early-born and late-born neurons are sequentially produced with a considerable time lag. Even if they are identical in their genetic and molecular specifications, they could develop different characteristics under the influences of the timing of their birth. In this review, we discuss the potential influences of "timing" as a generic parameter affecting neuronal differentiation, particularly on axon guidance and connections. These ideas have rarely been tested experimentally, but may provide a new strategy by which phenotypic diversity is increased in neurons.
Collapse
Affiliation(s)
- Tatsumi Hirata
- Division of Brain Function, National Institute of Genetics, 1111 Yata, Mishima, 411-8540, Japan; SOKENDAI (Graduate University for Advanced Studies), Japan.
| | - Lena Iwai
- Division of Brain Function, National Institute of Genetics, 1111 Yata, Mishima, 411-8540, Japan
| |
Collapse
|
10
|
Inokuchi K, Imamura F, Takeuchi H, Kim R, Okuno H, Nishizumi H, Bito H, Kikusui T, Sakano H. Nrp2 is sufficient to instruct circuit formation of mitral-cells to mediate odour-induced attractive social responses. Nat Commun 2017; 8:15977. [PMID: 28731029 PMCID: PMC5525001 DOI: 10.1038/ncomms15977] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 05/16/2017] [Indexed: 01/22/2023] Open
Abstract
Odour information induces various innate responses that are critical to the survival of the individual and for the species. An axon guidance molecule, Neuropilin 2 (Nrp2), is known to mediate targeting of olfactory sensory neurons (primary neurons), to the posteroventral main olfactory bulb (PV MOB) in mice. Here we report that Nrp2-positive (Nrp2+) mitral cells (MCs, second-order neurons) play crucial roles in transmitting attractive social signals from the PV MOB to the anterior part of medial amygdala (MeA). Semaphorin 3F, a repulsive ligand to Nrp2, regulates both migration of Nrp2+ MCs to the PV MOB and their axonal projection to the anterior MeA. In the MC-specific Nrp2 knockout mice, circuit formation of Nrp2+ MCs and odour-induced attractive social responses are impaired. In utero, electroporation demonstrates that activation of the Nrp2 gene in MCs is sufficient to instruct their circuit formation from the PV MOB to the anterior MeA.
Collapse
Affiliation(s)
- Kasumi Inokuchi
- Department of Brain Function, School of Medical Science, University of Fukui, Fukui 910-1193, Japan.,Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, Tokyo 113-0032, Japan
| | - Fumiaki Imamura
- Department of Pharmacology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA
| | - Haruki Takeuchi
- Department of Brain Function, School of Medical Science, University of Fukui, Fukui 910-1193, Japan
| | - Ryang Kim
- Department of Neurochemistry, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Hiroyuki Okuno
- Department of Neurochemistry, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Hirofumi Nishizumi
- Department of Brain Function, School of Medical Science, University of Fukui, Fukui 910-1193, Japan.,Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, Tokyo 113-0032, Japan
| | - Haruhiko Bito
- Department of Neurochemistry, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Takefumi Kikusui
- Department of Animal Science and Biotechnology, School of Veterinary Medicine, Azabu University, Sagamihara, Kanagawa 252-5201, Japan
| | - Hitoshi Sakano
- Department of Brain Function, School of Medical Science, University of Fukui, Fukui 910-1193, Japan
| |
Collapse
|
11
|
Mitsogiannis MD, Little GE, Mitchell KJ. Semaphorin-Plexin signaling influences early ventral telencephalic development and thalamocortical axon guidance. Neural Dev 2017; 12:6. [PMID: 28438183 PMCID: PMC5402653 DOI: 10.1186/s13064-017-0083-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 04/12/2017] [Indexed: 12/22/2022] Open
Abstract
Background Sensory processing relies on projections from the thalamus to the neocortex being established during development. Information from different sensory modalities reaching the thalamus is segregated into specialized nuclei, whose neurons then send inputs to cognate cortical areas through topographically defined axonal connections. Developing thalamocortical axons (TCAs) normally approach the cortex by extending through the subpallium; here, axonal navigation is aided by distributed guidance cues and discrete cell populations, such as the corridor neurons and the internal capsule (IC) guidepost cells. In mice lacking Semaphorin-6A, axons from the dorsal lateral geniculate nucleus (dLGN) bypass the IC and extend aberrantly in the ventral subpallium. The functions normally mediated by Semaphorin-6A in this system remain unknown, but might depend on interactions with Plexin-A2 and Plexin-A4, which have been implicated in other neurodevelopmental processes. Methods We performed immunohistochemical and neuroanatomical analyses of thalamocortical wiring and subpallial development in Sema6a and Plxna2; Plxna4 null mutant mice and analyzed the expression of these genes in relevant structures. Results In Plxna2; Plxna4 double mutants we discovered TCA pathfinding defects that mirrored those observed in Sema6a mutants, suggesting that Semaphorin-6A − Plexin-A2/Plexin-A4 signaling might mediate dLGN axon guidance at subpallial level. In order to understand where and when Semaphorin-6A, Plexin-A2 and Plexin-A4 may be required for proper subpallial TCA guidance, we then characterized their spatiotemporal expression dynamics during early TCA development. We observed that the thalamic neurons whose axons are misrouted in these mutants normally express Semaphorin-6A but not Plexin-A2 or Plexin-A4. By contrast, all three proteins are expressed in corridor cells and other structures in the developing basal ganglia. This finding could be consistent with an hypothetical action of Plexins as guidance signals through Sema6A as a receptor on dLGN axons, and/or with their indirect effect on TCA guidance due to functions in the morphogenesis of subpallial intermediate targets. In support of the latter possibility, we observed that in both Plxna2; Plxna4 and Sema6a mutants some IC guidepost cells abnormally localize in correspondence of the ventral path misrouted TCAs elongate into. Conclusions These findings implicate Semaphorin-6A − Plexin-A2/Plexin-A4 interactions in dLGN axon guidance and in the spatiotemporal organization of guidepost cell populations in the mammalian subpallium. Electronic supplementary material The online version of this article (doi:10.1186/s13064-017-0083-4) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Manuela D Mitsogiannis
- Smurfit Institute of Genetics, School of Genetics and Microbiology, Trinity College Dublin, Dublin 2, Ireland
| | - Graham E Little
- Smurfit Institute of Genetics, School of Genetics and Microbiology, Trinity College Dublin, Dublin 2, Ireland.,MRC Clinical Sciences Centre, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN, United Kingdom
| | - Kevin J Mitchell
- Smurfit Institute of Genetics, School of Genetics and Microbiology, Trinity College Dublin, Dublin 2, Ireland. .,Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin 2, Ireland. .,Developmental Neurogenetics, Smurfit Institute of Genetics, Trinity College Dublin, Dublin 2, Ireland.
| |
Collapse
|
12
|
Ravi N, Sanchez-Guardado L, Lois C, Kelsch W. Determination of the connectivity of newborn neurons in mammalian olfactory circuits. Cell Mol Life Sci 2017; 74:849-867. [PMID: 27695873 PMCID: PMC11107630 DOI: 10.1007/s00018-016-2367-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2016] [Revised: 08/24/2016] [Accepted: 09/13/2016] [Indexed: 12/24/2022]
Abstract
The mammalian olfactory bulb is a forebrain structure just one synapse downstream from the olfactory sensory neurons and performs the complex computations of sensory inputs. The formation of this sensory circuit is shaped through activity-dependent and cell-intrinsic mechanisms. Recent studies have revealed that cell-type specific connectivity and the organization of synapses in dendritic compartments are determined through cell-intrinsic programs already preset in progenitor cells. These progenitor programs give rise to subpopulations within a neuron type that have distinct synaptic organizations. The intrinsically determined formation of distinct synaptic organizations requires factors from contacting cells that match the cell-intrinsic programs. While certain genes control wiring within the newly generated neurons, other regulatory genes provide intercellular signals and are only expressed in neurons that will form contacts with the newly generated cells. Here, the olfactory system has provided a useful model circuit to reveal the factors regulating assembly of the highly structured connectivity in mammals.
Collapse
Affiliation(s)
- Namasivayam Ravi
- Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, 68159, Mannheim, Germany
| | - Luis Sanchez-Guardado
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA, 91125, USA
| | - Carlos Lois
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA, 91125, USA.
| | - Wolfgang Kelsch
- Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, 68159, Mannheim, Germany.
| |
Collapse
|
13
|
Temporal variations in early developmental decisions: an engine of forebrain evolution. Curr Opin Neurobiol 2017; 42:152-159. [PMID: 28092740 DOI: 10.1016/j.conb.2016.12.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 12/19/2016] [Accepted: 12/22/2016] [Indexed: 11/21/2022]
Abstract
Tight control of developmental timing is pivotal to many major processes in developmental biology, such as patterning, fate specification, cell cycle dynamics, cell migration and connectivity. Temporal change in these ontogenetic sequences is known as heterochrony, a major force in the evolution of body plans and organogenesis. In the last 5 years, studies in fish and rodents indicate that heterochrony in signaling during early development generates diversity in forebrain size and complexity. Here, we summarize these findings and propose that, additionally to spatio-temporal tuning of neurogenesis, temporal and quantitative modulation of signaling events drive pivotal changes in shape, size and complexity of the forebrain across evolution, participating to the generation of diversity in animal behavior and emergence of cognition.
Collapse
|
14
|
Lhx2 Determines Odorant Receptor Expression Frequency in Mature Olfactory Sensory Neurons. eNeuro 2016; 3:eN-NWR-0230-16. [PMID: 27822500 PMCID: PMC5086798 DOI: 10.1523/eneuro.0230-16.2016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2016] [Revised: 10/04/2016] [Accepted: 10/10/2016] [Indexed: 02/08/2023] Open
Abstract
A developmental program of epigenetic repression prepares each mammalian olfactory sensory neuron (OSN) to strongly express one allele from just one of hundreds of odorant receptor (OR) genes, but what completes this process of OR gene choice by driving the expression of this allele is incompletely understood. Conditional deletion experiments in mice demonstrate that Lhx2 is necessary for normal expression frequencies of nearly all ORs and all trace amine-associated receptors, irrespective of whether the deletion of Lhx2 is initiated in immature or mature OSNs. Given previous evidence that Lhx2 binds OR gene control elements, these findings indicate that Lhx2 is directly involved in driving OR expression. The data also support the conclusion that OR expression is necessary to allow immature OSNs to complete differentiation and become mature. In contrast to the robust effects of conditional deletion of Lhx2, the loss of Emx2 has much smaller effects and more often causes increased expression frequencies. Lhx2:Emx2 double mutants show opposing effects on Olfr15 expression that reveal independent effects of these two transcription factors. While Lhx2 is necessary for OR expression that supports OR gene choice, Emx2 can act differently; perhaps by helping to control the availability of OR genes for expression.
Collapse
|
15
|
Huilgol D, Tole S. Cell migration in the developing rodent olfactory system. Cell Mol Life Sci 2016; 73:2467-90. [PMID: 26994098 PMCID: PMC4894936 DOI: 10.1007/s00018-016-2172-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2015] [Revised: 02/08/2016] [Accepted: 03/01/2016] [Indexed: 02/06/2023]
Abstract
The components of the nervous system are assembled in development by the process of cell migration. Although the principles of cell migration are conserved throughout the brain, different subsystems may predominantly utilize specific migratory mechanisms, or may display unusual features during migration. Examining these subsystems offers not only the potential for insights into the development of the system, but may also help in understanding disorders arising from aberrant cell migration. The olfactory system is an ancient sensory circuit that is essential for the survival and reproduction of a species. The organization of this circuit displays many evolutionarily conserved features in vertebrates, including molecular mechanisms and complex migratory pathways. In this review, we describe the elaborate migrations that populate each component of the olfactory system in rodents and compare them with those described in the well-studied neocortex. Understanding how the components of the olfactory system are assembled will not only shed light on the etiology of olfactory and sexual disorders, but will also offer insights into how conserved migratory mechanisms may have shaped the evolution of the brain.
Collapse
Affiliation(s)
- Dhananjay Huilgol
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India
- Cold Spring Harbor Laboratory, Cold Spring Harbor, USA
| | - Shubha Tole
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India.
| |
Collapse
|
16
|
Netrin-G1 regulates fear-like and anxiety-like behaviors in dissociable neural circuits. Sci Rep 2016; 6:28750. [PMID: 27345935 PMCID: PMC4921862 DOI: 10.1038/srep28750] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 06/08/2016] [Indexed: 12/19/2022] Open
Abstract
In vertebrate mammals, distributed neural circuits in the brain are involved in emotion-related behavior. Netrin-G1 is a glycosyl-phosphatidylinositol-anchored synaptic adhesion molecule whose deficiency results in impaired fear-like and anxiety-like behaviors under specific circumstances. To understand the cell type and circuit specificity of these responses, we generated netrin-G1 conditional knockout mice with loss of expression in cortical excitatory neurons, inhibitory neurons, or thalamic neurons. Genetic deletion of netrin-G1 in cortical excitatory neurons resulted in altered anxiety-like behavior, but intact fear-like behavior, whereas loss of netrin-G1 in inhibitory neurons resulted in attenuated fear-like behavior, but intact anxiety-like behavior. These data indicate a remarkable double dissociation of fear-like and anxiety-like behaviors involving netrin-G1 in excitatory and inhibitory neurons, respectively. Our findings support a crucial role for netrin-G1 in dissociable neural circuits for the modulation of emotion-related behaviors, and provide genetic models for investigating the mechanisms underlying the dissociation. The results also suggest the involvement of glycosyl-phosphatidylinositol-anchored synaptic adhesion molecules in the development and pathogenesis of emotion-related behavior.
Collapse
|
17
|
Kawasawa YI, Salzberg AC, Li M, Šestan N, Greer CA, Imamura F. RNA-seq analysis of developing olfactory bulb projection neurons. Mol Cell Neurosci 2016; 74:78-86. [PMID: 27073125 DOI: 10.1016/j.mcn.2016.03.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 03/27/2016] [Accepted: 03/31/2016] [Indexed: 10/22/2022] Open
Abstract
Transmission of olfactory information to higher brain regions is mediated by olfactory bulb (OB) projection neurons, the mitral and tufted cells. Although mitral/tufted cells are often characterized as the OB counterpart of cortical projection neurons (also known as pyramidal neurons), they possess several unique morphological characteristics and project specifically to the olfactory cortices. Moreover, the molecular networks contributing to the generation of mitral/tufted cells during development are largely unknown. To understand the developmental patterns of gene expression in mitral/tufted cells in the OB, we performed transcriptome analyses targeting purified OB projection neurons at different developmental time points with next-generation RNA sequencing (RNA-seq). Through these analyses, we found 1202 protein-coding genes that are temporally differentially-regulated in developing projection neurons. Among them, 388 genes temporally changed their expression level only in projection neurons. The data provide useful resource to study the molecular mechanisms regulating development of mitral/tufted cells. We further compared the gene expression profiles of developing mitral/tufted cells with those of three cortical projection neuron subtypes, subcerebral projection neurons, corticothalamic projection neurons, and callosal projection neurons, and found that the molecular signature of developing olfactory projection neuron bears resemblance to that of subcerebral neurons. We also identified 3422 events that change the ratio of splicing isoforms in mitral/tufted cells during maturation. Interestingly, several genes expressed a novel isoform not previously reported. These results provide us with a broad perspective of the molecular networks underlying the development of OB projection neurons.
Collapse
Affiliation(s)
- Yuka Imamura Kawasawa
- Department of Pharmacology, Pennsylvania State University College of Medicine, 500 University Dr., Hershey, PA 17033, USA; Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, 500 University Dr., Hershey, PA 17033, USA; Institute for Personalized Medicine, Pennsylvania State University College of Medicine, 500 University Dr., Hershey, PA 17033, USA
| | - Anna C Salzberg
- Institute for Personalized Medicine, Pennsylvania State University College of Medicine, 500 University Dr., Hershey, PA 17033, USA
| | - Mingfeng Li
- Department of Neuroscience, Yale School of Medicine, 300 Cedar St., New Haven, CT 06510, USA
| | - Nenad Šestan
- Department of Neuroscience, Yale School of Medicine, 300 Cedar St., New Haven, CT 06510, USA; Kavli Institute for Neuroscience, Yale School of Medicine, 300 Cedar St., New Haven, CT 06510, USA
| | - Charles A Greer
- Department of Neuroscience, Yale School of Medicine, 300 Cedar St., New Haven, CT 06510, USA; Department of Neurosurgery, Yale School of Medicine, 300 Cedar St., New Haven, CT 06510, USA
| | - Fumiaki Imamura
- Department of Pharmacology, Pennsylvania State University College of Medicine, 500 University Dr., Hershey, PA 17033, USA.
| |
Collapse
|
18
|
Bastakis GG, Savvaki M, Stamatakis A, Vidaki M, Karagogeos D. Tag1 deficiency results in olfactory dysfunction through impaired migration of mitral cells. Development 2015; 142:4318-28. [PMID: 26525675 DOI: 10.1242/dev.123943] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 10/22/2015] [Indexed: 01/01/2023]
Abstract
The olfactory system provides mammals with the abilities to investigate, communicate and interact with their environment. These functions are achieved through a finely organized circuit starting from the nasal cavity, passing through the olfactory bulb and ending in various cortical areas. We show that the absence of transient axonal glycoprotein-1 (Tag1)/contactin-2 (Cntn2) in mice results in a significant and selective defect in the number of the main projection neurons in the olfactory bulb, namely the mitral cells. A subpopulation of these projection neurons is reduced in Tag1-deficient mice as a result of impaired migration. We demonstrate that the detected alterations in the number of mitral cells are well correlated with diminished odor discrimination ability and social long-term memory formation. Reduced neuronal activation in the olfactory bulb and the corresponding olfactory cortex suggest that Tag1 is crucial for the olfactory circuit formation in mice. Our results underpin the significance of a numerical defect in the mitral cell layer in the processing and integration of odorant information and subsequently in animal behavior.
Collapse
Affiliation(s)
- George G Bastakis
- Department of Basic Science, Faculty of Medicine, University of Crete and Institute of Molecular Biology and Biotechnology-FoRTH, Vassilika Vouton, Heraklion, Crete 71110, Greece
| | - Maria Savvaki
- Department of Basic Science, Faculty of Medicine, University of Crete and Institute of Molecular Biology and Biotechnology-FoRTH, Vassilika Vouton, Heraklion, Crete 71110, Greece
| | - Antonis Stamatakis
- Laboratory of Biology, Faculty of Nursing, School of Health Sciences, University of Athens, Papadiamantopoulou 123, Athens GR11527, Greece
| | - Marina Vidaki
- Department of Basic Science, Faculty of Medicine, University of Crete and Institute of Molecular Biology and Biotechnology-FoRTH, Vassilika Vouton, Heraklion, Crete 71110, Greece
| | - Domna Karagogeos
- Department of Basic Science, Faculty of Medicine, University of Crete and Institute of Molecular Biology and Biotechnology-FoRTH, Vassilika Vouton, Heraklion, Crete 71110, Greece
| |
Collapse
|
19
|
Imamura F, Greer CA. Segregated labeling of olfactory bulb projection neurons based on their birthdates. Eur J Neurosci 2014; 41:147-56. [PMID: 25393912 DOI: 10.1111/ejn.12784] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2014] [Revised: 10/01/2014] [Accepted: 10/13/2014] [Indexed: 11/30/2022]
Abstract
Mitral and tufted cells are the projection neurons of the olfactory bulb (OB). We previously reported that somata location and innervation patterns were different between early- and late-born mitral cells (Imamura et al., 2011). Here, we introduced a plasmid that drives the expression of a GFP gene into the mouse OB using in utero electroporation, and demonstrated that we can deliver the plasmid vectors into distinct subsets of OB projection neurons by changing the timing of electroporation after fertilisation. The electroporation performed at embryonic day (E)10 preferentially labeled mitral cells in the accessory OB and main OB mitral cells in dorsomedial mitral cell layer (MCL). In contrast, the E12 electroporation introduced the plasmid vectors preferentially into main OB mitral cells in the ventrolateral MCL and tufted cells. Combining these data with BrdU injections, we confirmed that E10 and E12 electroporation preferentially labeled early- and late-born projection neurons, respectively. This work introduces a novel method for segregated labeling of mouse olfactory bulb projection neurons based on their birthdates. With this technique we found that early- and late-born projection neurons extend their secondary dendrites in the deep and superficial external plexiform layer (EPL), respectively. Although a similar segregation has been suggested for mitral vs. tufted cell dendrites, we found mitral cells projecting secondary dendrites into the superficial EPL in E12-electroporated main OB. Our observations indicate that timing of neurogenesis regulates not only somata location and innervation patterns but also the laminar organisation of projection neuron dendrites in the EPL.
Collapse
Affiliation(s)
- Fumiaki Imamura
- Department of Pharmacology, Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA; Department of Neurosurgery, Yale University School of Medicine, New Haven, CT, USA
| | | |
Collapse
|
20
|
Nagayama S, Homma R, Imamura F. Neuronal organization of olfactory bulb circuits. Front Neural Circuits 2014; 8:98. [PMID: 25232305 PMCID: PMC4153298 DOI: 10.3389/fncir.2014.00098] [Citation(s) in RCA: 235] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 07/29/2014] [Indexed: 12/31/2022] Open
Abstract
Olfactory sensory neurons extend their axons solely to the olfactory bulb, which is dedicated to odor information processing. The olfactory bulb is divided into multiple layers, with different types of neurons found in each of the layers. Therefore, neurons in the olfactory bulb have conventionally been categorized based on the layers in which their cell bodies are found; namely, juxtaglomerular cells in the glomerular layer, tufted cells in the external plexiform layer, mitral cells in the mitral cell layer, and granule cells in the granule cell layer. More recently, numerous studies have revealed the heterogeneous nature of each of these cell types, allowing them to be further divided into subclasses based on differences in morphological, molecular, and electrophysiological properties. In addition, technical developments and advances have resulted in an increasing number of studies regarding cell types other than the conventionally categorized ones described above, including short-axon cells and adult-generated interneurons. Thus, the expanding diversity of cells in the olfactory bulb is now being acknowledged. However, our current understanding of olfactory bulb neuronal circuits is mostly based on the conventional and simplest classification of cell types. Few studies have taken neuronal diversity into account for understanding the function of the neuronal circuits in this region of the brain. This oversight may contribute to the roadblocks in developing more precise and accurate models of olfactory neuronal networks. The purpose of this review is therefore to discuss the expanse of existing work on neuronal diversity in the olfactory bulb up to this point, so as to provide an overall picture of the olfactory bulb circuit.
Collapse
Affiliation(s)
- Shin Nagayama
- Department of Neurobiology and Anatomy, The University of Texas Medical School at Houston Houston, TX, USA
| | - Ryota Homma
- Department of Neurobiology and Anatomy, The University of Texas Medical School at Houston Houston, TX, USA
| | - Fumiaki Imamura
- Department of Pharmacology, Pennsylvania State University College of Medicine Hershey, PA, USA
| |
Collapse
|
21
|
Gutiérrez-Castellanos N, Pardo-Bellver C, Martínez-García F, Lanuza E. The vomeronasal cortex - afferent and efferent projections of the posteromedial cortical nucleus of the amygdala in mice. Eur J Neurosci 2013; 39:141-58. [PMID: 24188795 DOI: 10.1111/ejn.12393] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 09/13/2013] [Accepted: 09/17/2013] [Indexed: 12/18/2022]
Abstract
Most mammals possess a vomeronasal system that detects predominantly chemical signals of biological relevance. Vomeronasal information is relayed to the accessory olfactory bulb (AOB), whose unique cortical target is the posteromedial cortical nucleus of the amygdala. This cortical structure should therefore be considered the primary vomeronasal cortex. In the present work, we describe the afferent and efferent connections of the posteromedial cortical nucleus of the amygdala in female mice, using anterograde (biotinylated dextranamines) and retrograde (Fluorogold) tracers, and zinc selenite as a tracer specific for zinc-enriched (putative glutamatergic) projections. The results show that the posteromedial cortical nucleus of the amygdala is strongly interconnected not only with the rest of the vomeronasal system (AOB and its target structures in the amygdala), but also with the olfactory system (piriform cortex, olfactory-recipient nuclei of the amygdala and entorhinal cortex). Therefore, the posteromedial cortical nucleus of the amygdala probably integrates olfactory and vomeronasal information. In addition, the posteromedial cortical nucleus of the amygdala shows moderate interconnections with the associative (basomedial) amygdala and with the ventral hippocampus, which may be involved in emotional and spatial learning (respectively) induced by chemical signals. Finally, the posteromedial cortical nucleus of the amygdala gives rise to zinc-enriched projections to the ventrolateral septum and the ventromedial striatum (including the medial islands of Calleja). This pattern of intracortical connections (with the olfactory cortex and hippocampus, mainly) and cortico-striatal excitatory projections (with the olfactory tubercle and septum) is consistent with its proposed nature as the primary vomeronasal cortex.
Collapse
Affiliation(s)
- Nicolás Gutiérrez-Castellanos
- Laboratori de Neuroanatomia Funcional Comparada, Departaments de Biologia Cellular i de Biologia Funcional, Facultat de Ciències Biològiques, Universitat de València, Burjassot, 46100, València, Spain
| | | | | | | |
Collapse
|
22
|
Nickell MD, Breheny P, Stromberg AJ, McClintock TS. Genomics of mature and immature olfactory sensory neurons. J Comp Neurol 2013; 520:2608-29. [PMID: 22252456 DOI: 10.1002/cne.23052] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The continuous replacement of neurons in the olfactory epithelium provides an advantageous model for investigating neuronal differentiation and maturation. By calculating the relative enrichment of every mRNA detected in samples of mature mouse olfactory sensory neurons (OSNs), immature OSNs, and the residual population of neighboring cell types, and then comparing these ratios against the known expression patterns of >300 genes, enrichment criteria that accurately predicted the OSN expression patterns of nearly all genes were determined. We identified 847 immature OSN-specific and 691 mature OSN-specific genes. The control of gene expression by chromatin modification and transcription factors, and neurite growth, protein transport, RNA processing, cholesterol biosynthesis, and apoptosis via death domain receptors, were overrepresented biological processes in immature OSNs. Ion transport (ion channels), presynaptic functions, and cilia-specific processes were overrepresented in mature OSNs. Processes overrepresented among the genes expressed by all OSNs were protein and ion transport, ER overload response, protein catabolism, and the electron transport chain. To more accurately represent gradations in mRNA abundance and identify all genes expressed in each cell type, classification methods were used to produce probabilities of expression in each cell type for every gene. These probabilities, which identified 9,300 genes expressed in OSNs, were 96% accurate at identifying genes expressed in OSNs and 86% accurate at discriminating genes specific to mature and immature OSNs. This OSN gene database not only predicts the genes responsible for the major biological processes active in OSNs, but also identifies thousands of never before studied genes that support OSN phenotypes.
Collapse
Affiliation(s)
- Melissa D Nickell
- Department of Physiology, University of Kentucky, Lexington, Kentucky 40536-0298, USA
| | | | | | | |
Collapse
|
23
|
Dual origins of the mammalian accessory olfactory bulb revealed by an evolutionarily conserved migratory stream. Nat Neurosci 2013; 16:157-65. [PMID: 23292680 DOI: 10.1038/nn.3297] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Accepted: 12/05/2012] [Indexed: 11/09/2022]
Abstract
The accessory olfactory bulb (AOB) is a critical olfactory structure that has been implicated in mediating social behavior. It receives input from the vomeronasal organ and projects to targets in the amygdaloid complex. Its anterior and posterior components (aAOB and pAOB) display molecular, connectional and functional segregation in processing reproductive and defensive and aggressive behaviors, respectively. We observed a dichotomy in the development of the projection neurons of the aAOB and pAOB in mice. We found that they had distinct sites of origin and that different regulatory molecules were required for their specification and migration. aAOB neurons arose locally in the rostral telencephalon, similar to main olfactory bulb neurons. In contrast, pAOB neurons arose caudally, from the neuroepithelium of the diencephalic-telencephalic boundary, from which they migrated rostrally to reach their destination. This unusual origin and migration is conserved in Xenopus, providing an insight into the origin of a key component of this system in evolution.
Collapse
|
24
|
Tbr2 deficiency in mitral and tufted cells disrupts excitatory-inhibitory balance of neural circuitry in the mouse olfactory bulb. J Neurosci 2012; 32:8831-44. [PMID: 22745484 DOI: 10.1523/jneurosci.5746-11.2012] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The olfactory bulb (OB) is the first relay station in the brain where odor information from the olfactory epithelium is integrated, processed through its intrinsic neural circuitry, and conveyed to higher olfactory centers. Compared with profound mechanistic insights into olfactory axon wiring from the nose to the OB, little is known about the molecular mechanisms underlying the formation of functional neural circuitry among various types of neurons inside the OB. T-box transcription factor Tbr2 is expressed in various types of glutamatergic excitatory neurons in the brain including the OB projection neurons, mitral and tufted cells. Here we generated conditional knockout mice in which the Tbr2 gene is inactivated specifically in mitral and tufted cells from late embryonic stages. Tbr2 deficiency caused cell-autonomous changes in molecular expression including a compensatory increase of another T-box member, Tbr1, and a concomitant shift of vesicular glutamate transporter (VGluT) subtypes from VGluT1 to VGluT2. Tbr2-deficient mitral and tufted cells also exhibited anatomical abnormalities in their dendritic morphology and projection patterns. Additionally, several non-cell-autonomous phenotypes were observed in parvalbumin-, calbindin-, and 5T4-positive GABAergic interneurons. Furthermore, the number of dendrodendritic reciprocal synapses between mitral/tufted cells and GABAergic interneurons was significantly reduced. Upon stimulation with odorants, larger numbers of mitral and tufted cells were activated in Tbr2 conditional knockout mice. These results suggest that Tbr2 is required for not only the proper differentiation of mitral and tufted cells, but also for the establishment of functional neuronal circuitry in the OB and maintenance of excitatory-inhibitory balance crucial for odor information processing.
Collapse
|
25
|
Huang CY, Chu D, Hwang WC, Tsaur ML. Coexpression of high-voltage-activated ion channels Kv3.4 and Cav1.2 in pioneer axons during pathfinding in the developing rat forebrain. J Comp Neurol 2012; 520:3650-72. [DOI: 10.1002/cne.23119] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
|
26
|
Hintiryan H, Gou L, Zingg B, Yamashita S, Lyden HM, Song MY, Grewal AK, Zhang X, Toga AW, Dong HW. Comprehensive connectivity of the mouse main olfactory bulb: analysis and online digital atlas. Front Neuroanat 2012; 6:30. [PMID: 22891053 PMCID: PMC3412993 DOI: 10.3389/fnana.2012.00030] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Accepted: 07/19/2012] [Indexed: 11/24/2022] Open
Abstract
We introduce the first open resource for mouse olfactory connectivity data produced as part of the Mouse Connectome Project (MCP) at UCLA. The MCP aims to assemble a whole-brain connectivity atlas for the C57Bl/6J mouse using a double coinjection tracing method. Each coinjection consists of one anterograde and one retrograde tracer, which affords the advantage of simultaneously identifying efferent and afferent pathways and directly identifying reciprocal connectivity of injection sites. The systematic application of double coinjections potentially reveals interaction stations between injections and allows for the study of connectivity at the network level. To facilitate use of the data, raw images are made publicly accessible through our online interactive visualization tool, the iConnectome, where users can view and annotate the high-resolution, multi-fluorescent connectivity data (www.MouseConnectome.org). Systematic double coinjections were made into different regions of the main olfactory bulb (MOB) and data from 18 MOB cases (~72 pathways; 36 efferent/36 afferent) currently are available to view in iConnectome within their corresponding atlas level and their own bright-field cytoarchitectural background. Additional MOB injections and injections of the accessory olfactory bulb (AOB), anterior olfactory nucleus (AON), and other olfactory cortical areas gradually will be made available. Analysis of connections from different regions of the MOB revealed a novel, topographically arranged MOB projection roadmap, demonstrated disparate MOB connectivity with anterior versus posterior piriform cortical area (PIR), and exposed some novel aspects of well-established cortical olfactory projections.
Collapse
Affiliation(s)
- Houri Hintiryan
- Laboratory of Neuro Imaging, Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles Los Angeles, CA, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
27
|
Hirata T, Kumada T, Kawasaki T, Furukawa T, Aiba A, Conquet F, Saga Y, Fukuda A. Guidepost neurons for the lateral olfactory tract: expression of metabotropic glutamate receptor 1 and innervation by glutamatergic olfactory bulb axons. Dev Neurobiol 2012; 72:1559-76. [PMID: 22539416 DOI: 10.1002/dneu.22030] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Accepted: 04/22/2012] [Indexed: 12/31/2022]
Abstract
The guidepost neurons for the lateral olfactory tract, which are called lot cells, are the earliest-generated neurons in the neocortex. They migrate tangentially and ventrally further down this tract, and provide scaffolding for the olfactory bulb axons projecting into this pathway. The molecular profiles of the lot cells are largely uncharacterized. We found that lot cells specifically express metabotropic glutamate receptor subtype-1 at a very early stage of development. This receptor is functionally competent and responds to a metabotropic glutamate receptor agonist with a transient increase in the intracellular calcium ion concentration. When the glutamatergic olfactory bulb axons were electrically stimulated, lot cells responded to the stimulation with a calcium increase mainly via ionotropic glutamate receptors, suggesting potential neurotransmission between the axons and lot cells during early development. Together with the finding that lot cells themselves are glutamatergic excitatory neurons, our results provide another notable example of precocious interactions between the projecting axons and their intermediate targets.
Collapse
Affiliation(s)
- Tatsumi Hirata
- Division of Brain Function, National Institute of Genetics, Yata, Mishima, Shizuoka, Japan.
| | | | | | | | | | | | | | | |
Collapse
|
28
|
Abstract
The olfactory peduncle, the region connecting the olfactory bulb with the basal forebrain, contains several neural areas that have received relatively little attention. The present work includes studies that provide an overview of the region in the mouse. An analysis of cell soma size in pars principalis (pP) of the anterior olfactory nucleus (AON) revealed considerable differences in tissue organization between mice and rats. An unbiased stereological study of neuron number in the cell-dense regions of pars externa (pE) and pP of the AON of 3-, 12-, and 24-month-old mice indicated that pE has about 16,500 cells in 0.043 mm(3) and pP about 58,300 cells in 0.307 mm(3) . Quantitative Golgi studies of pyramidal neurons in pP suggested that mouse neurons are similar to although smaller than those of the rat. An immunohistochemical analysis demonstrated that all peduncular regions (pE, pP, the dorsal peduncular cortex, ventral tenia tecta, and anterior olfactory tubercle and piriform cortex) have cells that express either calbindin, calretinin, parvalbumin, somatostatin, vasoactive intestinal polypeptide, neuropeptide Y, or cholecystokinin (antigens commonly co-expressed by subspecies of γ-aminobutyric acid [GABA]ergic neurons), although the relative numbers of each cell type differ between zones. Finally, an electron microscopic comparison of the organization of myelinated fibers in lateral olfactory tract in the anterior and posterior peduncle indicated that the region is less orderly in mice than in rats. The results provide a caveat for investigators who generalize data between species, as both similarities and differences between the laboratory mouse and rat were observed.
Collapse
Affiliation(s)
- Peter C Brunjes
- Department of Psychology, University of Virginia, Charlottesville, Virginia 22904, USA.
| | | | | |
Collapse
|
29
|
Abstract
Odor signals received by odorant receptors (ORs) expressed by olfactory sensory neurons (OSNs) in the olfactory epithelium (OE) are represented as an odor map in the olfactory bulb (OB). In the mouse, there are ~1,000 different OR species, and each OSN expresses only one functional OR gene in a monoallelic manner. Furthermore, OSN axons expressing the same type of OR converge on a specific target site in the OB, forming a glomerular structure. Because each glomerulus represents a single OR species, and a single odorant can interact with multiple OR species, odor signals received in the OE are converted into a topographic map of multiple glomeruli activated with varying magnitudes. Here we review recent progress in the study of the mammalian olfactory system, focusing on the formation of the olfactory map and the transmission of topographical information in the OB to the olfactory cortex to elicit various behaviors.
Collapse
Affiliation(s)
- Kensaku Mori
- Department of Physiology, Graduate School of Medicine, University of Tokyo, Tokyo 113-0033, Japan.
| | | |
Collapse
|
30
|
Timing of neurogenesis is a determinant of olfactory circuitry. Nat Neurosci 2011; 14:331-7. [PMID: 21297629 PMCID: PMC3046046 DOI: 10.1038/nn.2754] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Accepted: 01/11/2011] [Indexed: 02/07/2023]
Abstract
An odorant receptor map in mammals, that is constructed by the glomerular coalescence of sensory neuron axons in the olfactory bulb, is essential for proper odor information processing. However, how this map is linked with olfactory cortex is unknown. Here, we use a battery of methods, including various markers of cell division in combination with tracers of neuronal connections and time-lapse live imaging, to show that early- and late-generated mouse mitral cells become differentially distributed within the dorsal and ventral subdivisions of the odorant receptor map. In addition, we demonstrate that the late-generated mitral cells extend significantly stronger projections to the olfactory tubercle than the early-generated. Together, these data indicate that the odorant receptor map is developmentally linked to the olfactory cortices in part by the birthdate of mitral cells. This endows different olfactory cortical regions a role to process information from distinct regions of odorant receptor map.
Collapse
|
31
|
Abstract
AbstractThe olfactory system represents a perfect model to study the interactions between the central and peripheral nervous systems in order to establish a neural circuit during early embryonic development. In addition, another important feature of this system is the capability to integrate new cells generated in two neurogenic zones: the olfactory epithelium in the periphery and the wall of the lateral ventricles in the CNS, both during development and adulthood. In all these processes the combination and sequence of specific molecular signals plays a critical role in the wiring of the olfactory axons, as well as the precise location of the incoming cell populations to the olfactory bulb. The purpose of this review is to summarize recent insights into the cellular and molecular events that dictate cell settling position and axonal trajectories from their origin in the olfactory placode to the formation of synapses in the olfactory bulb to ensure rapid and reliable transmission of olfactory information from the nose to the brain.
Collapse
|
32
|
Kang N, Baum MJ, Cherry JA. Different profiles of main and accessory olfactory bulb mitral/tufted cell projections revealed in mice using an anterograde tracer and a whole-mount, flattened cortex preparation. Chem Senses 2010; 36:251-60. [PMID: 21177285 DOI: 10.1093/chemse/bjq120] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A whole-mount, flattened cortex preparation was developed to compare profiles of axonal projections from main olfactory bulb (MOB) and accessory olfactory bulb (AOB) mitral and tufted (M/T) cells. After injections of the anterograde tracer, Phaseolus vulgaris leucoagglutinin, mapping of labeled axons using a Neurolucida system showed that M/T cells in the AOB sent axons primarily to the medial and posterior lateral cortical amygdala, with minimal branching into the piriform cortex. By contrast, M/T cells in the MOB displayed a network of collaterals that branched off the primary axon at several levels of the lateral olfactory tract (LOT). Collaterals emerging from the LOT into the anterior piriform cortex were often observed crossing into the posterior piriform cortex. M/T cells in the dorsal MOB extended fewer collaterals from the primary axon in the rostral LOT than did M/T cells from the anterior or ventral MOB. MOB M/T cells that projected to the medial amygdala did not do so exclusively, also sending collaterals to the anterior cortical amygdala as well as to olfactory cortical regions. This arrangement may be related to the ability of social experience to modify the response of mice to volatile pheromones detected by the main olfactory system.
Collapse
Affiliation(s)
- Ningdong Kang
- Department of Biology, Boston University, Boston, MA 02215, USA
| | | | | |
Collapse
|
33
|
de Castro F. Wiring Olfaction: The Cellular and Molecular Mechanisms that Guide the Development of Synaptic Connections from the Nose to the Cortex. Front Neurosci 2009; 3:52. [PMID: 20582279 PMCID: PMC2858608 DOI: 10.3389/neuro.22.004.2009] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Accepted: 11/04/2009] [Indexed: 12/27/2022] Open
Abstract
Within the central nervous system, the olfactory system fascinates by its developmental and physiological particularities, and is one of the most studied models to understand the mechanisms underlying the guidance of growing axons to their appropriate targets. A constellation of contact-mediated (laminins, CAMs, ephrins, etc.) and secreted mechanisms (semaphorins, slits, growth factors, etc.) are known to play different roles in the establishment of synaptic interactions between the olfactory epithelium, olfactory bulb (OB) and olfactory cortex. Specific mechanisms of this system (including the amazing family of about 1000 different olfactory receptors) have been also proposed. In the last years, different reviews have focused in partial sights, specially in the mechanisms involved in the formation of the olfactory nerve, but a detailed review of the mechanisms implicated in the development of the connections among the different olfactory structures (olfactory epithelium, OB, olfactory cortex) remains to be written. In the present work, we afford this systematic review: the different cellular and molecular mechanisms which rule the formation of the olfactory nerve, the lateral olfactory tract and the intracortical connections, as well as the few data available regarding the accessory olfactory system. These mechanisms are compared, and the implications of the differences and similarities discussed in this fundamental scenario of ontogeny.
Collapse
Affiliation(s)
- Fernando de Castro
- Grupo de Neurobiología del Desarrollo-GNDe, Hospital Nacional de Parapléjicos Toledo, Spain
| |
Collapse
|
34
|
Abstract
The netrins are a family of extracellular proteins that direct cell and axon migration during embryogenesis. The name netrin is derived from the Sanskrit Netr, meaning 'guide'. Netrins are a family of extracellular proteins that direct cell and axon migration during embryogenesis. Three secreted netrins (netrins 1, 3 and 4), and two glycosylphosphatidylinositol (GPI)-anchored membrane proteins, netrins G1 and G2, have been identified in mammals. The secreted netrins are bifunctional, acting as attractants for some cell types and repellents for others. Receptors for the secreted netrins include the Deleted in Colorectal Cancer (DCC) family, the Down's syndrome cell adhesion molecule (DSCAM), and the UNC-5 homolog family: Unc5A, B, C and D in mammals. Netrin Gs do not appear to interact with these receptors, but regulate synaptic interactions between neurons by binding to the transmembrane netrin G ligands NGL1 and 2. The chemotropic function of secreted netrins has been best characterized with regard to axon guidance during the development of the nervous system. Extending axons are tipped by a flattened, membranous structure called the growth cone. Multiple extracellular guidance cues direct axonal growth cones to their ultimate targets where synapses form. Such cues can be locally derived (short-range), or can be secreted diffusible cues that allow target cells to signal axons from a distance (long-range). The secreted netrins function as short-range and long-range guidance cues in different circumstances. In addition to directing cell migration, functional roles for netrins have been identified in the regulation of cell adhesion, the maturation of cell morphology, cell survival and tumorigenesis.
Collapse
Affiliation(s)
- Sathyanath Rajasekharan
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec H3A 2B4, Canada
| | | |
Collapse
|
35
|
Woo J, Kwon SK, Kim E. The NGL family of leucine-rich repeat-containing synaptic adhesion molecules. Mol Cell Neurosci 2009; 42:1-10. [PMID: 19467332 DOI: 10.1016/j.mcn.2009.05.008] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Accepted: 05/14/2009] [Indexed: 10/20/2022] Open
Abstract
Cell adhesion molecules at neuronal synapses regulate diverse aspects of synaptic development, including axo-dendritic contact establishment, early synapse formation, and synaptic maturation. Recent studies have identified several synaptogenic adhesion molecules. The NGL (netrin-G ligand; LRRC4) family of synaptic cell adhesion molecules belongs to the superfamily of leucine-rich repeat (LRR) proteins. The three known members of the NGL family, NGL-1, NGL-2, and NGL-3, are mainly localized to the postsynaptic side of excitatory synapses, and interact with the presynaptic ligands, netrin-G1, netrin-G2, and LAR, respectively. NGLs interact with the abundant postsynaptic density (PSD) protein, PSD-95, and other postsynaptic proteins, including NMDA receptors. These interactions are thought to couple synaptic adhesion events to the assembly of synaptic proteins. In addition, NGL proteins regulate axonal outgrowth and lamina-specific dendritic segmentation, suggesting that the NGL-dependent adhesion system is important for the development of axons, dendrites, and synapses. Consistent with these functions, defects in NGLs and their ligands are associated with impaired learning and memory, hyperactivity, and an abnormal acoustic startle response in transgenic mice, and schizophrenia, bipolar disorder, and Rett syndrome in human patients.
Collapse
Affiliation(s)
- Jooyeon Woo
- National Creative Research Initiative Center for Synaptogenesis, Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea
| | | | | |
Collapse
|
36
|
Abstract
Netrins are a family of proteins that direct cell and axon migration during development. Three secreted netrins (netrin-1, -3 and -4) have been identified in mammals, in addition to two GPI-anchored membrane proteins, netrin-G1 and G2. Orthologues of netrin-1 play a highly conserved role as guidance cues at the midline of the developing CNS of vertebrates and some bilaterally symmetric invertebrates. In vertebrates, floor plate cells at the ventral midline of the embryonic neural tube secrete netrin-1, generating a circumferential gradient of netrin protein in the neuroepithelium. This protein gradient is bifunctional, attracting some axons to the midline and repelling others. Receptors for the secreted netrins include DCC (deleted in colorectal cancer) and the UNC5 homologues: UNC5A, B, C and D in mammals. DCC mediates chemoattraction, while repulsion requires an UNC5 homologue and, in some cases, DCC. The netrin-G proteins bind NGLs (netrin G ligands), single pass transmembrane proteins unrelated to either DCC or the UNC5 homologues. Netrin function is not limited to the developing CNS midline. Various netrins direct cell and axon migration throughout the embryonic CNS, and in some cases continue to be expressed in the mature nervous system. Furthermore, although initially identified for their ability to guide axons, functional roles for netrins have now been identified outside the nervous system where they influence tissue morphogenesis by directing cell migration and regulating cell-cell and cell-matrix adhesion.
Collapse
|
37
|
Pro-Sistiaga P, Mohedano-Moriano A, Ubeda-Bañon I, Del Mar Arroyo-Jimenez M, Marcos P, Artacho-Pérula E, Crespo C, Insausti R, Martinez-Marcos A. Convergence of olfactory and vomeronasal projections in the rat basal telencephalon. J Comp Neurol 2007; 504:346-62. [PMID: 17663431 DOI: 10.1002/cne.21455] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Olfactory and vomeronasal projections have been traditionally viewed as terminating in contiguous non-overlapping areas of the basal telencephalon. Original reports, however, described areas such as the anterior medial amygdala where both chemosensory afferents appeared to overlap. We addressed this issue by injecting dextran amines in the main or accessory olfactory bulbs of rats and the results were analyzed with light and electron microscopes. Simultaneous injections of different fluorescent dextran amines in the main and accessory olfactory bulbs were performed and the results were analyzed using confocal microscopy. Similar experiments with dextran amines in the olfactory bulbs plus FluoroGold in the bed nucleus of the stria terminalis indicate that neurons projecting through the stria terminalis could be integrating olfactory and vomeronasal inputs. Retrograde tracing experiments using FluoroGold or dextran amines confirm that areas of the rostral basal telencephalon receive inputs from both the main and accessory olfactory bulbs. While both inputs clearly converge in areas classically considered olfactory-recipient (nucleus of the lateral olfactory tract, anterior cortical amygdaloid nucleus, and cortex-amygdala transition zone) or vomeronasal-recipient (ventral anterior amygdala, bed nucleus of the accessory olfactory tract, and anteroventral medial amygdaloid nucleus), segregation is virtually complete at posterior levels such as the posteromedial and posterolateral cortical amygdalae. This provides evidence that areas so far considered receiving a single chemosensory modality are likely sites for convergent direct olfactory and vomeronasal inputs. Therefore, areas of the basal telencephalon should be reclassified as olfactory, vomeronasal, or mixed chemosensory structures, which could facilitate understanding of olfactory-vomeronasal interactions in functional studies.
Collapse
Affiliation(s)
- Palma Pro-Sistiaga
- Laboratorio de Neuroanatomía Humana, Departamento de Ciencias Médicas, Facultad de Medicina, Centro Regional de Investigaciones Biomédicas, Universidad de Castilla-La Mancha, 02006 Albacete, Spain
| | | | | | | | | | | | | | | | | |
Collapse
|
38
|
Nishimura-Akiyoshi S, Niimi K, Nakashiba T, Itohara S. Axonal netrin-Gs transneuronally determine lamina-specific subdendritic segments. Proc Natl Acad Sci U S A 2007; 104:14801-6. [PMID: 17785411 PMCID: PMC1964543 DOI: 10.1073/pnas.0706919104] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2006] [Indexed: 11/18/2022] Open
Abstract
Axons from a distinct group of neurons make contact with dendritic trees of target neurons in clearly segregated and laminated patterns, thereby forming functional units for processing multiple inputs of information in the vertebrate central nervous system. Whether and how dendrites acquire lamina-specific properties corresponding to each pathway is not known. We show here that vertebrate-specific membrane-anchored members of the UNC-6/netrin family, netrin-G1 and -G2, organize the lamina/pathway-specific differentiation of dendrites. Netrin-G1 and -G2 distribute on axons of different pathways and specifically interact with receptors NGL-1 and -2, respectively. In the hippocampus, parietal cortex, and piriform cortex, NGL-1 is concentrated in the dendritic segments corresponding to the lamina-specific termination of netrin-G1-positive axons, and NGL-2 is concentrated in distinct dendritic segments corresponding to the termination of netrin-G2-positive axons. In netrin-G1- and -G2-deficient mice, in which axonal path-finding is normal, the segmental distribution of NGL-1 and -2 is selectively disrupted, and the individual receptors are diffused along the dendrites. These findings indicate that transneuronal interactions of netrin-Gs and their specific receptors provide a molecular basis for the axonal innervation-dependent mechanism of postsynaptic membrane organization, and provide insight into the formation of the laminar structure within the dendrites.
Collapse
Affiliation(s)
| | - Kimie Niimi
- Research Resources Center, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Brain Science and Life Technology Research Foundation, 1-28-12 Narimasu, Itabashi, Tokyo 175-0094, Japan; and
| | - Toshiaki Nakashiba
- *Laboratory for Behavioral Genetics and
- The Picower Institute for Learning and Memory, RIKEN-MIT Neuroscience Research Center, Massachusetts Institute of Technology, Cambridge, MA 02139
| | | |
Collapse
|
39
|
Akins MR, Benson DL, Greer CA. Cadherin expression in the developing mouse olfactory system. J Comp Neurol 2007; 501:483-97. [PMID: 17278136 DOI: 10.1002/cne.21270] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Although odor receptors have been implicated in establishing the topography of olfactory sensory neurons (OSNs) in the olfactory bulb (OB), it is likely other molecules are also involved. The cadherins (CDHs) are a large family of cell adhesion molecules that mediate cell:cell interactions elsewhere in the central nervous system. However, their distribution and role in the olfactory system have remained largely unexplored. We previously demonstrated that intracellular binding partners of cadherins, the catenins, have unique spatiotemporal patterns of expression in the developing olfactory system. To further our understanding of cadherin function within the developing olfactory system, we now report on the localization of 11 classical cadherins-CDH1, 2, 3, 4, 5, 6, 8, 10, 11, 13, and 15. We demonstrate the expression of all but CDH5 and CDH15 in neuronal and/or glial cells in primary olfactory structures. CDH1 and CDH2 are expressed by OSNs; CDH2 expression closely parallels that seen for gamma-catenin in OSN axons. CDH3 and CDH11 are expressed by olfactory ensheathing glia, which surround OSN axons in the outer OB. CDH2, CDH4, and CDH6 are expressed within neuropil. CDH2, CDH4, CDH6, CDH8, CDH10, CDH11, and CDH13 are expressed by projection neurons within the main and accessory OBs. We conclude that cadherin proteins in the developing olfactory system are positioned to underlie the formation of the odorant map and local circuits within the OB.
Collapse
Affiliation(s)
- Michael R Akins
- Interdepartmental Neuroscience Graduate Program, Yale University School of Medicine, New Haven, Connecticut 06520-8082, USA
| | | | | |
Collapse
|
40
|
Saha B, Hari P, Huilgol D, Tole S. Dual role for LIM-homeodomain gene Lhx2 in the formation of the lateral olfactory tract. J Neurosci 2007; 27:2290-7. [PMID: 17329426 PMCID: PMC2092498 DOI: 10.1523/jneurosci.5571-06.2007] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The development of the olfactory system in vertebrates is a multistep process, in which several regulatory molecules are required at different stages. The development of the olfactory sensory epithelium and its projection to the olfactory bulb are both known to require the LIM-homeodomain transcription factor Lhx2. We examined whether Lhx2 plays a role in the development of the OB itself, as well as its projection to the olfactory cortex. Although there is no morphological OB protuberance in the Lhx2 mutant, mitral cells are normally specified and cluster in a displaced olfactory bulb-like structure (OBLS). The OBLS is not able to pioneer the lateral olfactory tract (LOT) projection in vivo or when provided control (host) telencephalic territory in an in vitro assay. Strikingly, the mutant OBLS is capable of projecting along the LOT if provided with an existing normal LOT in the host explant. This is the first report of a role for a transcription factor expressed in the OB that selectively affects the axon guidance but not the specification of mitral cells. Furthermore, the Lhx2 mutant lateral telencephalon does not support growth of an LOT projection from control OB explants. The defect correlates with the disruption of a cellular mechanism that is thought to be critical for LOT pathfinding: a specialized cell population, the "lot cells," is mislocalized in the Lhx2 mutant. In addition, the expression of Sema6A is aberrantly upregulated. Together, these findings reveal a dual role for Lhx2, in the OB as well as in the lateral telencephalon, for establishing the LOT projection.
Collapse
Affiliation(s)
- Bhaskar Saha
- Department of Biological Sciences, Tata Institute of Fundamental Research, Colaba, Mumbai 400 005, India
| | - Padmanabhan Hari
- Department of Biological Sciences, Tata Institute of Fundamental Research, Colaba, Mumbai 400 005, India
| | - Dhananjay Huilgol
- Department of Biological Sciences, Tata Institute of Fundamental Research, Colaba, Mumbai 400 005, India
| | - Shubha Tole
- Department of Biological Sciences, Tata Institute of Fundamental Research, Colaba, Mumbai 400 005, India
| |
Collapse
|
41
|
Fouquet C, Di Meglio T, Ma L, Kawasaki T, Long H, Hirata T, Tessier-Lavigne M, Chédotal A, Nguyen-Ba-Charvet KT. Robo1 and robo2 control the development of the lateral olfactory tract. J Neurosci 2007; 27:3037-45. [PMID: 17360927 PMCID: PMC6672566 DOI: 10.1523/jneurosci.0172-07.2007] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Revised: 02/13/2007] [Accepted: 02/14/2007] [Indexed: 02/02/2023] Open
Abstract
The development of olfactory bulb projections that form the lateral olfactory tract (LOT) is still poorly understood. It is known that the septum secretes Slit1 and Slit2 which repel olfactory axons in vitro and that in Slit1-/-;Slit2-/- mutant mice, the LOT is profoundly disrupted. However, the involvement of Slit receptors, the roundabout (Robo) proteins, in guiding LOT axons has not been demonstrated. We show here that both Robo1 and Robo2 receptors are expressed on early developing LOT axons, but that only Robo2 is present at later developmental stages. Olfactory bulb axons from Robo1-/-;Robo2-/- double-mutant mice are not repelled by Slit in vitro. The LOT develops normally in Robo1-/- mice, but is completely disorganized in Robo2-/- and Robo1-/-;Robo2-/- double-mutant embryos, with many LOT axons spreading along the ventral surface of the telencephalon. Finally, the position of lot1-expressing cells, which have been proposed to be the LOT guidepost cells, appears unaffected in Slit1-/-;Slit2-/- mice and in Robo1-/-;Robo2-/- mice. Together, our results indicate that Robo1 and Robo2 directly mediate the repulsive activity of Slit receptors on LOT axons, and are required for normal guidance of these axons in vivo.
Collapse
Affiliation(s)
- Coralie Fouquet
- Centre National de la Recherche Scientifique and
- Université Pierre et Marie Curie-Paris 6, Unité Mixte de Recherche 7102, Paris, 75005 France
| | - Thomas Di Meglio
- Centre National de la Recherche Scientifique and
- Université Pierre et Marie Curie-Paris 6, Unité Mixte de Recherche 7102, Paris, 75005 France
| | - Le Ma
- Howard Hughes Medical Institute, Department of Biological sciences, Stanford University, Stanford, California 94305
| | - Takahiko Kawasaki
- Division of Brain Function, National Institute of Genetics, Graduate University for advanced Studies (Sokendai), Yata 1111, Mishima 411-8540, Japan, and
| | - Hua Long
- Howard Hughes Medical Institute, Department of Biological sciences, Stanford University, Stanford, California 94305
| | - Tatsumi Hirata
- Division of Brain Function, National Institute of Genetics, Graduate University for advanced Studies (Sokendai), Yata 1111, Mishima 411-8540, Japan, and
| | - Marc Tessier-Lavigne
- Division of Brain Function, National Institute of Genetics, Graduate University for advanced Studies (Sokendai), Yata 1111, Mishima 411-8540, Japan, and
| | - Alain Chédotal
- Centre National de la Recherche Scientifique and
- Université Pierre et Marie Curie-Paris 6, Unité Mixte de Recherche 7102, Paris, 75005 France
| | - Kim T. Nguyen-Ba-Charvet
- Centre National de la Recherche Scientifique and
- Université Pierre et Marie Curie-Paris 6, Unité Mixte de Recherche 7102, Paris, 75005 France
| |
Collapse
|
42
|
Sato Y, Miyasaka N, Yoshihara Y. Hierarchical regulation of odorant receptor gene choice and subsequent axonal projection of olfactory sensory neurons in zebrafish. J Neurosci 2007; 27:1606-15. [PMID: 17301169 PMCID: PMC6673750 DOI: 10.1523/jneurosci.4218-06.2007] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2006] [Revised: 12/18/2006] [Accepted: 01/08/2007] [Indexed: 11/21/2022] Open
Abstract
In both Drosophila and mice, olfactory sensory neurons (OSNs) expressing a given odorant receptor (OR) project axons to specific glomeruli in the antennal lobe or olfactory bulb (OB), developing a topographic odor map. To gain insights into the modes of OR expression and axonal projection in zebrafish, we generated a bacterial artificial chromosome transgenic line carrying an OR gene cluster in which two OR-coding sequences, OR111-7 and OR103-1, were replaced with yellow fluorescent protein (YFP) and cyan fluorescent protein (CFP), respectively. In the transgenic embryos, YFP and CFP signals appear in small populations of OSNs at an early stage of development when OR expression is first observed. Time-lapse imaging of living embryos revealed that both YFP- and CFP-expressing OSNs project axons to the medial portion of the OB. This pattern of axonal projection is maintained in the adult transgenic fish, in which fluorescently labeled OSN axons target a topographically fixed cluster of glomeruli in the medial OB. Because the OR-coding sequences were replaced with fluorescent reporter genes, we examined which OR genes are expressed in YFP/CFP-expressing OSNs and found that the OR choice is mostly restricted to OR members within the same subfamily of the cluster. Furthermore, we found that the one receptor-one neuron rule is not always applicable to zebrafish OSNs and that multiple receptors-one neuron is true for a subpopulation of OSNs in both wild-type and transgenic fish. These data demonstrate two distinct modes of OR expression and suggest a model of the hierarchical regulation of OR gene choice and subsequent axonal projection in the zebrafish olfactory system.
Collapse
Affiliation(s)
- Yuki Sato
- Laboratory for Neurobiology of Synapse, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan, and
| | - Nobuhiko Miyasaka
- Laboratory for Neurobiology of Synapse, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan, and
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Osaka 560-0082, Japan
| | - Yoshihiro Yoshihara
- Laboratory for Neurobiology of Synapse, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan, and
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Osaka 560-0082, Japan
| |
Collapse
|
43
|
Walz A, Omura M, Mombaerts P. Development and topography of the lateral olfactory tract in the mouse: imaging by genetically encoded and injected fluorescent markers. ACTA ACUST UNITED AC 2006; 66:835-46. [PMID: 16673392 DOI: 10.1002/neu.20266] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In mammals, conventional odorants are detected by OSNs located in the main olfactory epithelium of the nose. These neurons project their axons to glomeruli, which are specialized structures of neuropil in the olfactory bulb. Within glomeruli, axons synapse onto dendrites of projection neurons, the mitral and tufted (M/T) cells. Genetic approaches to visualize axons of OSNs expressing a given odorant receptor have proven very useful in elucidating the organization of these projections to the olfactory bulb. Much less is known about the development and connectivity of the lateral olfactory tract (LOT), which is formed by axons of M/T cells connecting the olfactory bulb to central neural regions. Here, we have extended our genetic approach to mark M/T cells of the main olfactory bulb and their axons in the mouse, by targeted insertion of IRES-tauGFP in the neurotensin locus. In NT-GFP mice, we find that M/T cells of the main olfactory bulb mature and project axons as early as embryonic day 11.5. Final innervation of central areas is accomplished before the end of the second postnatal week. M/T cell axons that originate from small defined areas within the main olfactory bulb, as visualized by localized injections of fluorescent tracers in wild-type mice at postnatal days 1 to 3, follow a dual trajectory: a branch of tightly packed axons along the dorsal aspect of the LOT, and a more diffuse branch along the ventral aspect. The dorsal, but not the ventral, subdivision of the LOT exhibits a topographical segregation of axons coming from the dorsal versus ventral main olfactory bulb. The NT-GFP mouse strain should prove useful in further studies of development and topography of the LOT, from E11.5 until 2 weeks after birth.
Collapse
Affiliation(s)
- Andreas Walz
- The Rockefeller University, New York, New York 10021, USA
| | | | | |
Collapse
|
44
|
Blanchart A, De Carlos JA, López-Mascaraque L. Time frame of mitral cell development in the mice olfactory bulb. J Comp Neurol 2006; 496:529-43. [PMID: 16572431 DOI: 10.1002/cne.20941] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Along with tufted cells, mitral cells are the principal projection neurons in the olfactory bulb (OB). During the development of the OB, mitral cells migrate from the ventricular zone to the intermediate zone, where they begin to send axons along the lateral olfactory tract (LOT) to the cortical olfactory zones. Subsequently, they lose their tangential orientation, enabling them to make contact with the axons of the olfactory sensory neurons (OSN) that innervate the whole OB. Here, we investigated the distinct morphological features displayed by developing mitral cells and analyzed the relationship between the changes undertaken by these neurons and the arrival of the OSN axons. Immunostaining for specific markers of developing axons and dendrites, coupled with the use of fluorescent tracers, revealed the morphological changes, the continuous reorientation, and the final refinement that these cells undergo. We found that some of these changes are dependent on the arrival of the OSN axons. Indeed, we identified three main chronological events: 1) newly generated neurons become established in the intermediate zone and project to the LOT; 2) the cells reorient and spread their dendrites at the same time as OSN axons penetrate the OB (this is a sensitive period between embryonic day (E)15-16, in which the arrival of afferents establishes a spatial and temporal gradient that facilitates protoglomerulus and glomerulus formation); and 3) final refinement of the radially orientated cells to adopt a mature morphology. These results suggest that both afferent inputs and intrinsic factors participate to produce the well-defined sensory system.
Collapse
|
45
|
Sato Y, Miyasaka N, Yoshihara Y. Mutually exclusive glomerular innervation by two distinct types of olfactory sensory neurons revealed in transgenic zebrafish. J Neurosci 2006; 25:4889-97. [PMID: 15901770 PMCID: PMC6724860 DOI: 10.1523/jneurosci.0679-05.2005] [Citation(s) in RCA: 189] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The olfactory epithelium of fish contains two major types of olfactory sensory neurons (OSNs) that are distinct morphologically (ciliated vs microvillous) and possibly functionally. Here, we found that these OSNs express different sets of signal transduction machineries: the ciliated OSNs express OR-type odorant receptors, cyclic nucleotide-gated channel A2 subunit, and olfactory marker protein (OMP), whereas the microvillous OSNs express V2R-type receptors and transient receptor potential channel C2 (TRPC2). To visualize patterns of axonal projection from the two types of OSNs to the olfactory bulb (OB), we generated transgenic zebrafish in which spectrally distinct fluorescent proteins are expressed in the ciliated and microvillous OSNs under the control of OMP and TRPC2 gene promoters, respectively. An observation of whole-mount OB in adult double-transgenic zebrafish revealed that the ciliated OSNs project axons mostly to the dorsal and medial regions of the OB, whereas the microvillous OSNs project axons to the lateral region of the OB. A careful histological examination of OB sections clarified that the axons from the two distinct types of OSNs target different glomeruli in a mutually exclusive manner. This segregation is already established at very early developmental stages in zebrafish embryos. These findings clearly demonstrate the relationships among cell morphology, molecular signatures, and axonal terminations of the two distinct types of OSNs and suggest that the two segregated neural pathways are responsible for coding and processing of different types of odor information in the zebrafish olfactory system.
Collapse
Affiliation(s)
- Yuki Sato
- Laboratory for Neurobiology of Synapse, RIKEN Brain Science Institute, Saitama 351-0198, Japan
| | | | | |
Collapse
|
46
|
Kawasaki T, Ito K, Hirata T. Netrin 1 regulates ventral tangential migration of guidepost neurons in the lateral olfactory tract. Development 2006; 133:845-53. [PMID: 16439477 DOI: 10.1242/dev.02257] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the developing nervous system, functional neural networks are constructed with intricate coordination of neuronal migrations and axonal projections. We have previously reported a ventral tangential migration of a special type of cortical neurons, lot cells, in the mouse embryo. These neurons originate from the ventricular zone of the entire neocortex, tangentially migrate in the surface layer of the neocortex into the ventral direction, align in the future pathway of the lateral olfactory tract (LOT) and eventually guide the projection of LOT axons. In this study, we developed an organotypic culture system to investigate the regulation of this cell migration in the developing telencephalon. Our data show that the neocortex contains the signals that direct lot cells ventrally, that the ganglionic eminence excludes lot cells by repelling the migration and that lot cells are attracted to netrin 1, an axon guidance factor. Furthermore, we demonstrate that mutations in the genes encoding netrin 1 and its functional receptor Dcc lead to inappropriate distribution of lot cells and subsequent partial disruption of LOT projection. These results suggest that netrin 1 regulates the migration of lot cells and LOT projections, possibly by ensuring the correct distribution of these guidepost neurons.
Collapse
Affiliation(s)
- Takahiko Kawasaki
- Division of Brain Function, National Institute of Genetics, Graduate University for Advanced Studies, SOKENDAI, Yata 1111, Mishima 411-8540, Japan
| | | | | |
Collapse
|
47
|
Fritzsch B, Muirhead KA, Feng F, Gray BD, Ohlsson-Wilhelm BM. Diffusion and imaging properties of three new lipophilic tracers, NeuroVue Maroon, NeuroVue Red and NeuroVue Green and their use for double and triple labeling of neuronal profile. Brain Res Bull 2005; 66:249-58. [PMID: 16023922 PMCID: PMC1513641 DOI: 10.1016/j.brainresbull.2005.05.016] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2005] [Revised: 04/11/2005] [Accepted: 05/05/2005] [Indexed: 10/25/2022]
Abstract
We describe here diffusion and imaging properties of three new lipophilic tracers, NeuroVue Maroon (near infrared), NeuroVue Red and NeuroVue Green. Using pair-wise comparisons between the new dyes and existing dyes (DiI, DiA, DiD, DiO, PKH2, PKH26) applied to the left and the right side of fixed spinal cord preparations, we show that NeuroVue Maroon (excitation maximum 647 nm) surpasses all other dyes in this study in signal to noise ratio. We also present data showing the utility of these new dyes for both double labeling and triple labeling in combination with each other or existing lipophilic tracers. Using mice bearing the PLP-eGFP transgene, we demonstrate that either NeuroVue Maroon or NeuroVue Red can readily be combined with eGFP labeling. Double labeling experiments using NeuroVue Red and eGFP allowed us to demonstrate that every fiber in the neonatal ear is surrounded by developing Schwann cells.
Collapse
Affiliation(s)
- B Fritzsch
- Department of Biomedical Sciences, Creighton University, Omaha, NE 68178, USA.
| | | | | | | | | |
Collapse
|
48
|
Yoshihara SI, Omichi K, Yanazawa M, Kitamura K, Yoshihara Y. Arx homeobox gene is essential for development of mouse olfactory system. Development 2005; 132:751-62. [PMID: 15677725 DOI: 10.1242/dev.01619] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The olfactory system provides an excellent model in which to study cell proliferation, migration, differentiation, axon guidance, dendritic morphogenesis, and synapse formation. We report here crucial roles of the Arx homeobox gene in the developing olfactory system by analyzing its mutant phenotypes. Arx protein was expressed strongly in the interneurons and weakly in the radial glia of the olfactory bulb, but in neither the olfactory sensory neurons nor bulbar projection neurons. Arx-deficient mice showed severe anatomical abnormalities in the developing olfactory system: (1) size reduction of the olfactory bulb, (2) reduced proliferation and impaired entry into the olfactory bulb of interneuron progenitors, (3) loss of tyrosine hydroxylase-positive periglomerular cells, (4) disorganization of the layer structure of the olfactory bulb, and (5) abnormal axonal termination of olfactory sensory neurons in an unusual axon-tangled structure, the fibrocellular mass. Thus, Arx is required for not only the proper developmental processes of Arx-expressing interneurons, but also the establishment of functional olfactory neural circuitry by affecting Arx-non-expressing sensory neurons and projection neurons. These findings suggest a likely role of Arx in regulating the expression of putative instructive signals produced in the olfactory bulb for the proper innervation of olfactory sensory axons.
Collapse
Affiliation(s)
- Sei-ichi Yoshihara
- Laboratory for Neurobiology of Synapse, RIKEN Brain Science Institute, Wako-shi, Saitama 351-0198, Japan
| | | | | | | | | |
Collapse
|