1
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Ohman L, Hanbali L, Krimm R. Taste arbor structural variability analyzed across taste regions. J Comp Neurol 2023; 531:743-758. [PMID: 36740741 PMCID: PMC10082444 DOI: 10.1002/cne.25459] [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: 05/23/2022] [Revised: 01/04/2023] [Accepted: 01/13/2023] [Indexed: 02/07/2023]
Abstract
Taste ganglion neurons are functionally and molecularly diverse, but until recently morphological diversity was completely unexplored. Specifically, taste arbors (the portion of the neuron within the taste bud) vary in structure, but the reason for this variability is unclear. Here, we analyzed structural variability in taste arbors to determine which factors determine their morphological diversity. To characterize arbor morphology and its relationship to taste bud cells capable of transducing taste stimuli (taste-transducing cell) number and type, we utilized sparse cell genetic labeling of taste ganglion neurons in combination with whole-mount immunohistochemistry. Reconstruction of 151 taste arbors revealed variation in arbor size, complexity, and symmetry. Overall, taste arbors exist on a continuum of complexity, cannot be categorized into discrete morphological groups, and do not have stereotyped endings. Arbor size/complexity was not related to the size of the taste bud in which it was located or the type of taste-transducing cell contacted (membranes within 180 nm). Instead, arbors could be broadly categorized into three groups: large asymmetrical arbors contacting many taste-transducing cells, small symmetrical arbors contacting one or two taste-transducing cells, and unbranched arbors. Neurons with multiple arbors had arbors in more than one of these categories, indicating that this variability is not an intrinsic feature of neuron type. Instead, we speculate that arbor structure is determined primarily by nerve fiber remodeling in response to cell turnover and that large asymmetrical arbors represent a particularly plastic state.
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Affiliation(s)
- Lisa Ohman
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY 40292, USA
| | - Lama Hanbali
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY 40292, USA
| | - Robin Krimm
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY 40292, USA
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2
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Pomaville MB, Wright KM. Follicle-innervating Aδ-low threshold mechanoreceptive neurons form receptive fields through homotypic competition. Neural Dev 2023; 18:2. [PMID: 37106422 PMCID: PMC10134579 DOI: 10.1186/s13064-023-00170-2] [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: 09/23/2022] [Accepted: 04/20/2023] [Indexed: 04/29/2023] Open
Abstract
The mammalian somatosensory system is comprised of multiple neuronal populations that form specialized, highly organized sensory endings in the skin. The organization of somatosensory endings is essential to their functions, yet the mechanisms which regulate this organization remain unclear. Using a combination of genetic and molecular labeling approaches, we examined the development of mouse hair follicle-innervating low-threshold mechanoreceptors (LTMRs) and explored competition for innervation targets as a mechanism involved in the patterning of their receptive fields. We show that follicle innervating neurons are present in the skin at birth and that LTMR receptive fields gradually add follicle-innervating endings during the first two postnatal weeks. Using a constitutive Bax knockout to increase the number of neurons in adult animals, we show that two LTMR subtypes have differential responses to an increase in neuronal population size: Aδ-LTMR neurons shrink their receptive fields to accommodate the increased number of neurons innervating the skin, while C-LTMR neurons do not. Our findings suggest that competition for hair follicles to innervate plays a role in the patterning and organization of follicle-innervating LTMR neurons.
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Affiliation(s)
- Matthew B Pomaville
- Vollum Institute, Oregon Health and Science University, Portland, OR, 97239, USA
- Department of Cell, Developmental, and Cancer Biology, Cell and Developmental Biology Graduate Program, Oregon Health and Science University, Portland, OR, 97239, USA
| | - Kevin M Wright
- Vollum Institute, Oregon Health and Science University, Portland, OR, 97239, USA.
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3
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Qi L, Iskols M, Shi D, Reddy P, Walker C, Lezgiyeva K, Voisin T, Pawlak M, Kuchroo VK, Chiu I, Ginty DD, Sharma N. A DRG genetic toolkit reveals molecular, morphological, and functional diversity of somatosensory neuron subtypes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.22.537932. [PMID: 37131664 PMCID: PMC10153270 DOI: 10.1101/2023.04.22.537932] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Mechanical and thermal stimuli acting on the skin are detected by morphologically and physiologically distinct sensory neurons of the dorsal root ganglia (DRG). Achieving a holistic view of how this diverse neuronal population relays sensory information from the skin to the central nervous system (CNS) has been challenging with existing tools. Here, we used transcriptomic datasets of the mouse DRG to guide development and curation of a genetic toolkit to interrogate transcriptionally defined DRG neuron subtypes. Morphological analysis revealed unique cutaneous axon arborization areas and branching patterns of each subtype. Physiological analysis showed that subtypes exhibit distinct thresholds and ranges of responses to mechanical and/or thermal stimuli. The somatosensory neuron toolbox thus enables comprehensive phenotyping of most principal sensory neuron subtypes. Moreover, our findings support a population coding scheme in which the activation thresholds of morphologically and physiologically distinct cutaneous DRG neuron subtypes tile multiple dimensions of stimulus space.
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Affiliation(s)
- Lijun Qi
- Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115
| | - Michael Iskols
- Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115
| | - David Shi
- Department of Molecular Pharmacology and Therapeutics, Department of Systems Biology, Columbia University, New York, NY
| | - Pranav Reddy
- Department of Molecular Pharmacology and Therapeutics, Department of Systems Biology, Columbia University, New York, NY
| | - Christopher Walker
- Department of Molecular Pharmacology and Therapeutics, Department of Systems Biology, Columbia University, New York, NY
| | - Karina Lezgiyeva
- Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115
| | - Tiphaine Voisin
- Department of Immunology, Harvard Medical School, Boston, MA 02115
| | - Mathias Pawlak
- Evergrande Center for Immunologic Diseases, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02115, USA
| | - Vijay K. Kuchroo
- Evergrande Center for Immunologic Diseases, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02115, USA
| | - Isaac Chiu
- Department of Immunology, Harvard Medical School, Boston, MA 02115
| | - David D. Ginty
- Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115
| | - Nikhil Sharma
- Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115
- Department of Molecular Pharmacology and Therapeutics, Department of Systems Biology, Columbia University, New York, NY
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4
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Peterman E, Quitevis EJA, Black EC, Horton EC, Aelmore RL, White E, Sagasti A, Rasmussen JP. Zebrafish cutaneous injury models reveal that Langerhans cells engulf axonal debris in adult epidermis. Dis Model Mech 2023; 16:dmm049911. [PMID: 36876992 PMCID: PMC10110399 DOI: 10.1242/dmm.049911] [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: 09/29/2022] [Accepted: 02/28/2023] [Indexed: 03/07/2023] Open
Abstract
Somatosensory neurons extend enormous peripheral axons to the skin, where they detect diverse environmental stimuli. Somatosensory peripheral axons are easily damaged due to their small caliber and superficial location. Axonal damage results in Wallerian degeneration, creating vast quantities of cellular debris that phagocytes must remove to maintain organ homeostasis. The cellular mechanisms that ensure efficient clearance of axon debris from stratified adult skin are unknown. Here, we established zebrafish scales as a tractable model to study axon degeneration in the adult epidermis. Using this system, we demonstrated that skin-resident immune cells known as Langerhans cells engulf the majority of axon debris. In contrast to immature skin, adult keratinocytes did not significantly contribute to debris removal, even in animals lacking Langerhans cells. Our study establishes a powerful new model for studying Wallerian degeneration and identifies a new function for Langerhans cells in maintenance of adult skin homeostasis following injury. These findings have important implications for pathologies that trigger somatosensory axon degeneration.
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Affiliation(s)
- Eric Peterman
- Department of Biology, University of Washington, Seattle, WA 98195, USA
| | | | - Erik C. Black
- Department of Biology, University of Washington, Seattle, WA 98195, USA
- Molecular and Cellular Biology Program, University of Washington, Seattle, WA 98195, USA
| | - Emma C. Horton
- Department of Biology, University of Washington, Seattle, WA 98195, USA
| | - Rune L. Aelmore
- Department of Biology, University of Washington, Seattle, WA 98195, USA
| | - Ethan White
- Department of Biology, University of Washington, Seattle, WA 98195, USA
| | - Alvaro Sagasti
- Molecular, Cell and Developmental Biology Department, University of California, Los Angeles, CA 90095, USA
- Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
| | - Jeffrey P. Rasmussen
- Department of Biology, University of Washington, Seattle, WA 98195, USA
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA 98109, USA
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5
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Rosa JB, Nassman KY, Sagasti A. Sensory axons induce epithelial lipid microdomain remodeling and determine the distribution of junctions in the epidermis. Mol Biol Cell 2023; 34:ar5. [PMID: 36322392 PMCID: PMC9816649 DOI: 10.1091/mbc.e22-09-0396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 10/21/2022] [Accepted: 10/25/2022] [Indexed: 12/23/2022] Open
Abstract
Epithelial cell properties are determined by the polarized distribution of membrane lipids, the cytoskeleton, and adhesive junctions. Epithelia are often profusely innervated, but little work has addressed how neurites affect epithelial organization. We previously found that basal keratinocytes in the zebrafish epidermis enclose axons in ensheathment channels sealed by autotypic junctions. Here we characterized how axons remodel cell membranes, the cytoskeleton, and junctions in basal keratinocytes. At the apical surface of basal keratinocytes, axons organized lipid microdomains quantitatively enriched in reporters for PI(4,5)P2 and liquid-ordered (Lo) membranes. Lipid microdomains supported the formation of cadherin-enriched, F-actin protrusions, which wrapped around axons, likely initiating ensheathment. In the absence of axons, cadherin-enriched microdomains formed on basal cells but did not organize into contiguous domains. Instead, these isolated domains formed heterotypic junctions with periderm cells, a distinct epithelial cell type. Thus, axon endings dramatically remodel polarized epithelial components and regulate epidermal adhesion.
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Affiliation(s)
- Jeffrey B. Rosa
- Department of Molecular, Cell and Developmental Biology and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
| | - Khaled Y. Nassman
- Department of Molecular, Cell and Developmental Biology and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
| | - Alvaro Sagasti
- Department of Molecular, Cell and Developmental Biology and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
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6
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Yamauchi Y, Matsukura H, Motone K, Ueda M, Aoki W. Evaluation of a library of loxP variants with a wide range of recombination efficiencies by Cre. PLoS One 2022; 17:e0276657. [PMID: 36269789 PMCID: PMC9586403 DOI: 10.1371/journal.pone.0276657] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 10/11/2022] [Indexed: 11/18/2022] Open
Abstract
Sparse labeling of individual cells is an important approach in neuroscience and many other fields of research. Various methods have been developed to sparsely label only a small population of cells; however, there is no simple and reproducible strategy for managing the probability of sparse labeling at desired levels. Here, we aimed to develop a novel methodology based on the Cre-lox system to regulate sparseness at desired levels, and we purely analyzed cleavage efficiencies of loxP mutants by Cre. We hypothesized that mutations in the loxP sequence reduce the recognition efficiency by Cre, which enables the regulation of the sparseness level of gene expression. In this research, we mutagenized the loxP sequence and analyzed a library of loxP variants. We evaluated more than 1000 mutant loxP sequences, including mutants with reduced excision efficiencies by Cre ranging from 0.51% to 59%. This result suggests that these mutant loxP sequences can be useful in regulating the sparseness of genetic labeling at desired levels.
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Affiliation(s)
- Yuji Yamauchi
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, Japan
- Japan Society for the Promotion of Science, Sakyo-ku, Kyoto, Japan
| | - Hidenori Matsukura
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Keisuke Motone
- Paul G. Allen School of Computer Science and Engineering, University of Washington, Seattle, Washington, United States of America
| | - Mitsuyoshi Ueda
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Wataru Aoki
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, Japan
- * E-mail:
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7
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Scott-Solomon E, Hsu YC. Neurobiology, Stem Cell Biology, and Immunology: An Emerging Triad for Understanding Tissue Homeostasis and Repair. Annu Rev Cell Dev Biol 2022; 38:419-446. [PMID: 36201298 PMCID: PMC10085582 DOI: 10.1146/annurev-cellbio-120320-032429] [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] [Indexed: 02/04/2023]
Abstract
The peripheral nervous system (PNS) endows animals with the remarkable ability to sense and respond to a dynamic world. Emerging evidence shows the PNS also participates in tissue homeostasis and repair by integrating local changes with organismal and environmental changes. Here, we provide an in-depth summary of findings delineating the diverse roles of peripheral nerves in modulating stem cell behaviors and immune responses under steady-state conditions and in response to injury and duress, with a specific focus on the skin and the hematopoietic system. These examples showcase how elucidating neuro-stem cell and neuro-immune cell interactions provides a conceptual framework that connects tissue biology and local immunity with systemic bodily changes to meet varying demands. They also demonstrate how changes in these interactions can manifest in stress, aging, cancer, and inflammation, as well as how these findings can be harnessed to guide the development of new therapeutics.
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Affiliation(s)
- Emily Scott-Solomon
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, Massachusetts, USA; ,
- Harvard Stem Cell Institute, Cambridge, Massachusetts, USA
| | - Ya-Chieh Hsu
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, Massachusetts, USA; ,
- Harvard Stem Cell Institute, Cambridge, Massachusetts, USA
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8
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Cheng XT, Huang N, Sheng ZH. Programming axonal mitochondrial maintenance and bioenergetics in neurodegeneration and regeneration. Neuron 2022; 110:1899-1923. [PMID: 35429433 PMCID: PMC9233091 DOI: 10.1016/j.neuron.2022.03.015] [Citation(s) in RCA: 58] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 01/04/2022] [Accepted: 03/10/2022] [Indexed: 12/11/2022]
Abstract
Mitochondria generate ATP essential for neuronal growth, function, and regeneration. Due to their polarized structures, neurons face exceptional challenges to deliver mitochondria to and maintain energy homeostasis throughout long axons and terminal branches where energy is in high demand. Chronic mitochondrial dysfunction accompanied by bioenergetic failure is a pathological hallmark of major neurodegenerative diseases. Brain injury triggers acute mitochondrial damage and a local energy crisis that accelerates neuron death. Thus, mitochondrial maintenance defects and axonal energy deficits emerge as central problems in neurodegenerative disorders and brain injury. Recent studies have started to uncover the intrinsic mechanisms that neurons adopt to maintain (or reprogram) axonal mitochondrial density and integrity, and their bioenergetic capacity, upon sensing energy stress. In this review, we discuss recent advances in how neurons maintain a healthy pool of axonal mitochondria, as well as potential therapeutic strategies that target bioenergetic restoration to power neuronal survival, function, and regeneration.
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Affiliation(s)
- Xiu-Tang Cheng
- Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Room 2B-215, 35 Convent Drive, Bethesda, MD 20892-3706, USA
| | - Ning Huang
- Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Room 2B-215, 35 Convent Drive, Bethesda, MD 20892-3706, USA
| | - Zu-Hang Sheng
- Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Room 2B-215, 35 Convent Drive, Bethesda, MD 20892-3706, USA.
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9
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Morphological pseudotime ordering and fate mapping reveal diversification of cerebellar inhibitory interneurons. Nat Commun 2022; 13:3433. [PMID: 35701402 PMCID: PMC9197879 DOI: 10.1038/s41467-022-30977-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 05/20/2022] [Indexed: 12/15/2022] Open
Abstract
Understanding how diverse neurons are assembled into circuits requires a framework for describing cell types and their developmental trajectories. Here we combine genetic fate-mapping, pseudotemporal profiling of morphogenesis, and dual morphology and RNA labeling to resolve the diversification of mouse cerebellar inhibitory interneurons. Molecular layer interneurons (MLIs) derive from a common progenitor population but comprise diverse dendritic-, somatic-, and axon initial segment-targeting interneurons. Using quantitative morphology from 79 mature MLIs, we identify two discrete morphological types and presence of extensive within-class heterogeneity. Pseudotime trajectory inference using 732 developmental morphologies indicate the emergence of distinct MLI types during migration, before reaching their final positions. By comparing MLI identities from morphological and transcriptomic signatures, we demonstrate the dissociation between these modalities and that subtype divergence can be resolved from axonal morphogenesis prior to marker gene expression. Our study illustrates the utility of applying single-cell methods to quantify morphology for defining neuronal diversification.
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10
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Lehnert BP, Santiago C, Huey EL, Emanuel AJ, Renauld S, Africawala N, Alkislar I, Zheng Y, Bai L, Koutsioumpa C, Hong JT, Magee AR, Harvey CD, Ginty DD. Mechanoreceptor synapses in the brainstem shape the central representation of touch. Cell 2021; 184:5608-5621.e18. [PMID: 34637701 PMCID: PMC8556359 DOI: 10.1016/j.cell.2021.09.023] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 08/10/2021] [Accepted: 09/15/2021] [Indexed: 10/20/2022]
Abstract
Mammals use glabrous (hairless) skin of their hands and feet to navigate and manipulate their environment. Cortical maps of the body surface across species contain disproportionately large numbers of neurons dedicated to glabrous skin sensation, in part reflecting a higher density of mechanoreceptors that innervate these skin regions. Here, we find that disproportionate representation of glabrous skin emerges over postnatal development at the first synapse between peripheral mechanoreceptors and their central targets in the brainstem. Mechanoreceptor synapses undergo developmental refinement that depends on proximity of their terminals to glabrous skin, such that those innervating glabrous skin make synaptic connections that expand their central representation. In mice incapable of sensing gentle touch, mechanoreceptors innervating glabrous skin still make more powerful synapses in the brainstem. We propose that the skin region a mechanoreceptor innervates controls the developmental refinement of its central synapses to shape the representation of touch in the brain.
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Affiliation(s)
- Brendan P Lehnert
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Celine Santiago
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Erica L Huey
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Alan J Emanuel
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Sophia Renauld
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Nusrat Africawala
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Ilayda Alkislar
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Yang Zheng
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Ling Bai
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Charalampia Koutsioumpa
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Jennifer T Hong
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Alexandra R Magee
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Christopher D Harvey
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - David D Ginty
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA; Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA.
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11
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Ishida H, Zhang Y, Gomez R, Shannonhouse J, Son H, Banik R, Kim YS. In Vivo Calcium Imaging Visualizes Incision-Induced Primary Afferent Sensitization and Its Amelioration by Capsaicin Pretreatment. J Neurosci 2021; 41:8494-8507. [PMID: 34452938 PMCID: PMC8513701 DOI: 10.1523/jneurosci.0457-21.2021] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 07/27/2021] [Accepted: 08/23/2021] [Indexed: 02/06/2023] Open
Abstract
Previous studies have shown that infiltration of capsaicin into the surgical site can prevent incision-induced spontaneous pain like behaviors and heat hyperalgesia. In the present study, we aimed to monitor primary sensory neuron Ca2+ activity in the intact dorsal root ganglia (DRG) using Pirt-GCaMP3 male and female mice pretreated with capsaicin or vehicle before the plantar incision. Intraplantar injection of capsaicin (0.05%) significantly attenuated spontaneous pain, mechanical, and heat hypersensitivity after plantar incision. The Ca2+ response in in vivo DRG and in in situ spinal cord was significantly enhanced in the ipsilateral side compared with contralateral side or naive control. Primary sensory nerve fiber length was significantly decreased in the incision skin area in capsaicin-pretreated animals detected by immunohistochemistry and placental alkaline phosphatase (PLAP) staining. Thus, capsaicin pretreatment attenuates incisional pain by suppressing Ca2+ response because of degeneration of primary sensory nerve fibers in the skin.SIGNIFICANCE STATEMENT Postoperative surgery pain is a major health and economic problem worldwide with ∼235 million major surgical procedures annually. Approximately 50% of these patients report uncontrolled or poorly controlled postoperative pain. However, mechanistic studies of postoperative surgery pain in primary sensory neurons have been limited to in vitro models or small numbers of neurons. Using an innovative, distinctive, and interdisciplinary in vivo populational dorsal root ganglia (DRG) imaging (>1800 neurons/DRG) approach, we revealed increased DRG neuronal Ca2+ activity from postoperative pain mouse model. This indicates widespread DRG primary sensory neuron plasticity. Increased neuronal Ca2+ activity occurs among various sizes of neurons but mostly in small-diameter and medium-diameter nociceptors. Capsaicin pretreatment as a therapeutic option significantly attenuates Ca2+ activity and postoperative pain.
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Affiliation(s)
- Hirotake Ishida
- Department of Oral and Maxillofacial Surgery, University of Texas Health and Science Center at San Antonio, Texas, 78229
| | - Yan Zhang
- Department of Oral and Maxillofacial Surgery, University of Texas Health and Science Center at San Antonio, Texas, 78229
| | - Ruben Gomez
- Department of Oral and Maxillofacial Surgery, University of Texas Health and Science Center at San Antonio, Texas, 78229
| | - John Shannonhouse
- Department of Oral and Maxillofacial Surgery, University of Texas Health and Science Center at San Antonio, Texas, 78229
| | - Hyeonwi Son
- Department of Oral and Maxillofacial Surgery, University of Texas Health and Science Center at San Antonio, Texas, 78229
| | - Ratan Banik
- Department of Anesthesiology, School of Medicine, University of Minnesota, Minneapolis, Minnesota, 55455
| | - Yu Shin Kim
- Department of Oral and Maxillofacial Surgery, University of Texas Health and Science Center at San Antonio, Texas, 78229
- Programs in Integrated Biomedical Sciences, Translational Sciences, Biomedical Engineering, Radiological Sciences, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229
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12
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Handler A, Ginty DD. The mechanosensory neurons of touch and their mechanisms of activation. Nat Rev Neurosci 2021; 22:521-537. [PMID: 34312536 PMCID: PMC8485761 DOI: 10.1038/s41583-021-00489-x] [Citation(s) in RCA: 114] [Impact Index Per Article: 38.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/24/2021] [Indexed: 02/07/2023]
Abstract
Our sense of touch emerges from an array of mechanosensory structures residing within the fabric of our skin. These tactile end organ structures convert innocuous forces acting on the skin into electrical signals that propagate to the CNS via the axons of low-threshold mechanoreceptors (LTMRs). Our rich capacity for tactile discrimination arises from the dissimilar intrinsic properties of the LTMR subtypes that innervate different regions of the skin and the structurally distinct end organ complexes with which they associate. These end organ structures comprise a range of non-neuronal cell types, which may themselves actively contribute to the transformation of tactile forces into neural impulses within the LTMR afferents. Although the mechanism and the site of transduction across end organs remain unclear, PIEZO2 has emerged as the principal mechanosensitive channel involved in light touch of the skin. Here we review the physiological properties of LTMR subtypes and discuss how features of their cutaneous end organ complexes shape subtype-specific tuning.
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Affiliation(s)
- Annie Handler
- Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, Boston, MA, USA
| | - David D Ginty
- Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, Boston, MA, USA.
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13
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Hernandez-Nunez L, Chen A, Budelli G, Berck ME, Richter V, Rist A, Thum AS, Cardona A, Klein M, Garrity P, Samuel ADT. Synchronous and opponent thermosensors use flexible cross-inhibition to orchestrate thermal homeostasis. SCIENCE ADVANCES 2021; 7:7/35/eabg6707. [PMID: 34452914 PMCID: PMC8397275 DOI: 10.1126/sciadv.abg6707] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 07/09/2021] [Indexed: 06/13/2023]
Abstract
Body temperature homeostasis is essential and reliant upon the integration of outputs from multiple classes of cooling- and warming-responsive cells. The computations that integrate these outputs are not understood. Here, we discover a set of warming cells (WCs) and show that the outputs of these WCs combine with previously described cooling cells (CCs) in a cross-inhibition computation to drive thermal homeostasis in larval Drosophila WCs and CCs detect temperature changes using overlapping combinations of ionotropic receptors: Ir68a, Ir93a, and Ir25a for WCs and Ir21a, Ir93a, and Ir25a for CCs. WCs mediate avoidance to warming while cross-inhibiting avoidance to cooling, and CCs mediate avoidance to cooling while cross-inhibiting avoidance to warming. Ambient temperature-dependent regulation of the strength of WC- and CC-mediated cross-inhibition keeps larvae near their homeostatic set point. Using neurophysiology, quantitative behavioral analysis, and connectomics, we demonstrate how flexible integration between warming and cooling pathways can orchestrate homeostatic thermoregulation.
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Affiliation(s)
- Luis Hernandez-Nunez
- Department of Physics, Harvard University, Cambridge, MA 02138, USA.
- Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
- Systems, Synthetic, and Quantitative Biology PhD Program, Harvard University, Cambridge, Boston, MA 02115, USA
| | - Alicia Chen
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
- Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
- Harvard College, Harvard University, Cambridge, MA 02138, USA
| | - Gonzalo Budelli
- National Center for Behavioral Genomics, Brandeis University, Waltham, MA 02454, USA
- Department of Biology, Brandeis University, Waltham, MA 02454, USA
- Volen National Center for Complex Systems, Brandeis University, Waltham, MA 02454, USA
| | - Matthew E Berck
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Vincent Richter
- University of Leipzig, Institute of Biology, Talstraße 33, 04103 Leipzig, Germany
| | - Anna Rist
- University of Leipzig, Institute of Biology, Talstraße 33, 04103 Leipzig, Germany
| | - Andreas S Thum
- University of Leipzig, Institute of Biology, Talstraße 33, 04103 Leipzig, Germany
| | - Albert Cardona
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Mason Klein
- Department of Physics, University of Miami, Coral Gables, FL 33124, USA.
| | - Paul Garrity
- National Center for Behavioral Genomics, Brandeis University, Waltham, MA 02454, USA.
- Department of Biology, Brandeis University, Waltham, MA 02454, USA
- Volen National Center for Complex Systems, Brandeis University, Waltham, MA 02454, USA
| | - Aravinthan D T Samuel
- Department of Physics, Harvard University, Cambridge, MA 02138, USA.
- Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
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14
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Huang T, Ohman LC, Clements AV, Whiddon ZD, Krimm RF. Variable Branching Characteristics of Peripheral Taste Neurons Indicates Differential Convergence. J Neurosci 2021; 41:4850-4866. [PMID: 33875572 PMCID: PMC8260161 DOI: 10.1523/jneurosci.1935-20.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 03/26/2021] [Accepted: 04/10/2021] [Indexed: 11/21/2022] Open
Abstract
Taste neurons are functionally and molecularly diverse, but their morphologic diversity remains completely unexplored. Using sparse cell genetic labeling, we provide the first reconstructions of peripheral taste neurons. The branching characteristics across 96 taste neurons show surprising diversity in their complexities. Individual neurons had 1-17 separate arbors entering between one and seven taste buds, 18 of these neurons also innervated non-taste epithelia. Axon branching characteristics are similar in gustatory neurons from male and female mice. Cluster analysis separated the neurons into four groups according to branch complexity. The primary difference between clusters was the amount of the nerve fiber within the taste bud available to contact taste-transducing cells. Consistently, we found that the maximum number of taste-transducing cells capable of providing convergent input onto individual gustatory neurons varied with a range of 1-22 taste-transducing cells. Differences in branching characteristics across neurons indicate that some neurons likely receive input from a larger number of taste-transducing cells than other neurons (differential convergence). By dividing neurons into two groups based on the type of taste-transducing cell most contacted, we found that neurons contacting primarily sour transducing cells were more heavily branched than those contacting primarily sweet/bitter/umami transducing cells. This suggests that neuron morphologies may differ across functional taste quality. However, the considerable remaining variability within each group also suggests differential convergence within each functional taste quality. Each possibility has functional implications for the system.SIGNIFICANCE STATEMENT Taste neurons are considered relay cells, communicating information from taste-transducing cells to the brain, without variation in morphology. By reconstructing peripheral taste neuron morphologies for the first time, we found that some peripheral gustatory neurons are simply branched, and can receive input from only a few taste-transducing cells. Other taste neurons are heavily branched, contacting many more taste-transducing cells than simply branched neurons. Based on the type of taste-transducing cell contacted, branching characteristics are predicted to differ across (and within) quality types (sweet/bitter/umami vs sour). Therefore, functional differences between neurons likely depends on the number of taste-transducing cells providing input and not just the type of cell providing input.
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Affiliation(s)
- Tao Huang
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, Kentucky 40202
| | - Lisa C Ohman
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, Kentucky 40202
| | - Anna V Clements
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, Kentucky 40202
| | - Zachary D Whiddon
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, Kentucky 40202
| | - Robin F Krimm
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, Kentucky 40202
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15
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Yin C, Peterman E, Rasmussen JP, Parrish JZ. Transparent Touch: Insights From Model Systems on Epidermal Control of Somatosensory Innervation. Front Cell Neurosci 2021; 15:680345. [PMID: 34135734 PMCID: PMC8200473 DOI: 10.3389/fncel.2021.680345] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Accepted: 04/28/2021] [Indexed: 12/28/2022] Open
Abstract
Somatosensory neurons (SSNs) densely innervate our largest organ, the skin, and shape our experience of the world, mediating responses to sensory stimuli including touch, pressure, and temperature. Historically, epidermal contributions to somatosensation, including roles in shaping innervation patterns and responses to sensory stimuli, have been understudied. However, recent work demonstrates that epidermal signals dictate patterns of SSN skin innervation through a variety of mechanisms including targeting afferents to the epidermis, providing instructive cues for branching morphogenesis, growth control and structural stability of neurites, and facilitating neurite-neurite interactions. Here, we focus onstudies conducted in worms (Caenorhabditis elegans), fruit flies (Drosophila melanogaster), and zebrafish (Danio rerio): prominent model systems in which anatomical and genetic analyses have defined fundamental principles by which epidermal cells govern SSN development.
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Affiliation(s)
- Chang Yin
- Department of Biology, University of Washington, Seattle, WA, United States
| | - Eric Peterman
- Department of Biology, University of Washington, Seattle, WA, United States
| | | | - Jay Z Parrish
- Department of Biology, University of Washington, Seattle, WA, United States
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16
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Pomaville MB, Wright KM. Immunohistochemical and Genetic Labeling of Hairy and Glabrous Skin Innervation. Curr Protoc 2021; 1:e121. [PMID: 33950580 PMCID: PMC8162737 DOI: 10.1002/cpz1.121] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Cutaneous innervation is an essential component of the mammalian sensory nervous system. During development, genetically and morphologically diverse subtypes of sensory neurons use distinct molecular pathways to innervate end organs or form free nerve endings in glabrous and hairy skin. Peripheral neurons can be damaged by acute injury or degenerate due to chronic conditions including diabetes and chemotherapy, leading to peripheral neuropathy. The analysis of skin and cutaneous innervation can be applied to many research endeavors, from developmental neuroscience to pharmaceutical testing. Due to the natural hydrophobicity and heterogenous makeup of the skin (dense, keratinized cells as well as sparse, extracellular-matrix-bound cells), its histological analysis presents unique challenges compared to that of many other tissues. This series of protocols describes histological methods for generalized immunohistochemistry and subtype-specific genetic labeling of sensory neurons in mouse skin in both whole-mount and section formats. We provide detailed methodology of tissue preparation for hairy and glabrous skin, several types of labeling, and counting of hair follicles in flat-mounted mouse skin. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Cryosectioning and immunostaining of mouse hairy skin Alternate Protocol 1: Alternate method for preparation and fixation of mouse hairy skin Basic Protocol 2: Sectioning of mouse paw glabrous skin Basic Protocol 3: Whole-mount immunolabeling of mouse skin Basic Protocol 4: Sparse labeling of skin-innervating neurons with a Cre-dependent membrane-bound alkaline phosphatase reporter Alternate Protocol 2: Sparse labeling of skin-innervating neurons with a Cre-dependent fluorescent reporter Basic Protocol 5: Oil Red O staining of skin.
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Affiliation(s)
- Matthew B Pomaville
- Department of Cell, Developmental, and Cancer Biology, Oregon Health & Science University, Portland, Oregon
- Vollum Institute, Oregon Health & Science University, Portland, Oregon
| | - Kevin M Wright
- Vollum Institute, Oregon Health & Science University, Portland, Oregon
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17
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Cheng XT, Sheng ZH. Developmental regulation of microtubule-based trafficking and anchoring of axonal mitochondria in health and diseases. Dev Neurobiol 2021; 81:284-299. [PMID: 32302463 PMCID: PMC7572491 DOI: 10.1002/dneu.22748] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Revised: 01/09/2020] [Accepted: 04/09/2020] [Indexed: 12/20/2022]
Abstract
Mitochondria are cellular power plants that supply most of the ATP required in the brain to power neuronal growth, function, and regeneration. Given their extremely polarized structures and extended long axons, neurons face an exceptional challenge to maintain energy homeostasis in distal axons, synapses, and growth cones. Anchored mitochondria serve as local energy sources; therefore, the regulation of mitochondrial trafficking and anchoring ensures that these metabolically active areas are adequately supplied with ATP. Chronic mitochondrial dysfunction is a hallmark feature of major aging-related neurodegenerative diseases, and thus, anchored mitochondria in aging neurons need to be removed when they become dysfunctional. Investigations into the regulation of microtubule (MT)-based trafficking and anchoring of axonal mitochondria under physiological and pathological circumstances represent an important emerging area. In this short review article, we provide an updated overview of recent in vitro and in vivo studies showing (1) how mitochondria are transported and positioned in axons and synapses during neuronal developmental and maturation stages, and (2) how altered mitochondrial motility and axonal energy deficits in aging nervous systems link to neurodegeneration and regeneration in a disease or injury setting. We also highlight a major role of syntaphilin as a key MT-based regulator of axonal mitochondrial trafficking and anchoring in mature neurons.
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Affiliation(s)
- Xiu-Tang Cheng
- Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health, Room 2B-215, 35 Convent Drive, Bethesda, Maryland 20892-3706, USA
| | - Zu-Hang Sheng
- Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health, Room 2B-215, 35 Convent Drive, Bethesda, Maryland 20892-3706, USA
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18
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von Buchholtz LJ, Ghitani N, Lam RM, Licholai JA, Chesler AT, Ryba NJP. Decoding Cellular Mechanisms for Mechanosensory Discrimination. Neuron 2021; 109:285-298.e5. [PMID: 33186546 PMCID: PMC9909446 DOI: 10.1016/j.neuron.2020.10.028] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 09/27/2020] [Accepted: 10/20/2020] [Indexed: 01/29/2023]
Abstract
Single-cell RNA-sequencing and in vivo functional imaging provide expansive but disconnected views of neuronal diversity. Here, we developed a strategy for linking these modes of classification to explore molecular and cellular mechanisms responsible for detecting and encoding touch. By broadly mapping function to neuronal class, we uncovered a clear transcriptomic logic responsible for the sensitivity and selectivity of mammalian mechanosensory neurons. Notably, cell types with divergent gene-expression profiles often shared very similar properties, but we also discovered transcriptomically related neurons with specialized and divergent functions. Applying our approach to knockout mice revealed that Piezo2 differentially tunes all types of mechanosensory neurons with marked cell-class dependence. Together, our data demonstrate how mechanical stimuli recruit characteristic ensembles of transcriptomically defined neurons, providing rules to help explain the discriminatory power of touch. We anticipate a similar approach could expose fundamental principles governing representation of information throughout the nervous system.
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Affiliation(s)
- Lars J. von Buchholtz
- National Institute of Dental and Craniofacial Research, NIH, Bethesda MD 20892, USA,These authors contributed equally
| | - Nima Ghitani
- National Center for Integrative and Complementary Health, Bethesda MD 20892, USA,These authors contributed equally
| | - Ruby M. Lam
- National Center for Integrative and Complementary Health, Bethesda MD 20892, USA,Brown-National Institutes of Health Graduate Partnerships Program, Brown University, Providence, RI, USA
| | - Julia A. Licholai
- National Institute of Dental and Craniofacial Research, NIH, Bethesda MD 20892, USA,Brown-National Institutes of Health Graduate Partnerships Program, Brown University, Providence, RI, USA
| | - Alexander T. Chesler
- National Center for Integrative and Complementary Health, Bethesda MD 20892, USA,Lead contact: ,Correspondence: or
| | - Nicholas J. P. Ryba
- National Institute of Dental and Craniofacial Research, NIH, Bethesda MD 20892, USA,Correspondence: or
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19
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Russell DF, Warnock TC, Zhang W, Rogers DE, Neiman LL. Large-Scale Convergence of Receptor Cell Arrays Onto Afferent Terminal Arbors in the Lorenzinian Electroreceptors of Polyodon. Front Neuroanat 2020; 14:50. [PMID: 33192338 PMCID: PMC7604333 DOI: 10.3389/fnana.2020.00050] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Accepted: 07/13/2020] [Indexed: 12/31/2022] Open
Abstract
Certain sensory receptors contain many transducers, converging onto few afferents. Convergence creates star-topology neural networks, of iterative parallel organization, that may yield special functional properties. We quantitated large-scale convergence in electroreceptors on the rostrum of preadult paddlefish, Polyodon spathula (Acipenseriforme vertebrates), and analyzed the afferent terminal branching underlying the convergence. From neurophysiological mapping, a recorded afferent innervated 23.3 ± 9.1 (range 6-45) ampullary organs, and innervated every ampullary organ within the receptive field's sharp boundary. Ampullary organs each contained ∼665 Lorenzinian receptor cells, from imaging and modeling. We imaged three serial types of afferent branching at electroreceptors, after immunofluorescent labeling for neurite filaments, glial sheaths, or nodal ion channels, or by DiI tracing. (i) Myelinated tree: Each of 3.08 ± 0.51 (2-4) parallel afferents from a cranial nerve (ALLn) entered a receptive field from deeper tissue, then branched into a laminar tree of large myelinated dendrites, parallel to the skin, that branched radially until ∼9 extremities with heminodes, which were candidate sites of spike encoders. (ii) Inline transition: Each myelinated extremity led distally into local unmyelinated arbors originating at inline branching structures covered by terminal (satellite) glia. The unmyelinated transition zones included globular afferent modules, 4-6 microns wide, from which erupted fine fascicles of parallel submicron neurites, a possibly novel type of neuronal branching. The neurite fascicles formed loose bundles projecting ∼105 microns distally to innervate local groups of ∼3 adjacent ampullary organs. (iii) Radial arbors: Receptor cells in an electrosensory neuroepithelium covering the basal pole of each ampullary organ were innervated by bouton endings of radial neurites, unmyelinated and submicron, forming a thin curviplanar lamina distal to the lectin+ basal lamina. The profuse radial neurites diverged from thicker (∼2 micron) basolateral trunks. Overall, an average Polyodon electroreceptor formed a star topology array of ∼9 sensor groups. Total convergence ratios were 15,495 ± 6,052 parallel receptor cells per afferent per mean receptive field, assuming 100% innervation. Large-scale convergence likely increases the signal-to-noise ratio (SNR) of stimulus encoding into spiking afferent output, increasing receiver sensitivity. Unmyelinated arbors may also regenerate and repair the afferent innervation of ampullary organs. LSID: urn:lsid:zoobank.org:act:09BCF04C-3C3C-4B6C-9DC9-A2BF43087369.
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Affiliation(s)
- David F Russell
- Department of Biological Sciences, Ohio University, Athens, OH, United States.,Department of Physics and Astronomy, Ohio University, Athens, OH, United States.,Neuroscience Program, Ohio University, Athens, OH, United States
| | - Thomas C Warnock
- Department of Physics and Astronomy, Ohio University, Athens, OH, United States
| | - Wenjuan Zhang
- Honors Tutorial College, Ohio University, Athens, OH, United States
| | - Desmon E Rogers
- Department of Physics and Astronomy, Ohio University, Athens, OH, United States
| | - Lilia L Neiman
- Department of Biological Sciences, Ohio University, Athens, OH, United States
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20
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Xing Y, Steele HR, Hilley HB, Zhu Y, Lawson K, Niehoff T, Han L. Visualizing the Itch-Sensing Skin Arbors. J Invest Dermatol 2020; 141:1308-1316. [PMID: 33091423 DOI: 10.1016/j.jid.2020.08.030] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 08/10/2020] [Accepted: 08/26/2020] [Indexed: 12/15/2022]
Abstract
Diverse sensory neurons exhibit distinct neuronal morphologies with a variety of axon terminal arborizations subserving their functions. Because of its clinical significance, the molecular and cellular mechanisms of itch are being intensely studied. However, a complete analysis of itch-sensing terminal arborization is missing. Using an MrgprC11CreERT2 transgenic mouse line, we labeled a small subset of itch-sensing neurons that express multiple itch-related molecules including MrgprA3, MrgprC11, histamine receptor H1, IL-31 receptor, 5-hydroxytryptamine receptor 1F, natriuretic precursor peptide B, and neuromedin B. By combining sparse genetic labeling and whole-mount placental alkaline phosphatase histochemistry, we found that itch-sensing skin arbors exhibit free endings with extensive axonal branching in the superficial epidermis and large receptive fields. These results revealed the unique morphological characteristics of itch-sensing neurons and provide intriguing insights into the basic mechanisms of itch transmission.
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Affiliation(s)
- Yanyan Xing
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Haley R Steele
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Henry B Hilley
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Yuyan Zhu
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Katy Lawson
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Taylor Niehoff
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Liang Han
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA.
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21
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Neubarth NL, Emanuel AJ, Liu Y, Springel MW, Handler A, Zhang Q, Lehnert BP, Guo C, Orefice LL, Abdelaziz A, DeLisle MM, Iskols M, Rhyins J, Kim SJ, Cattel SJ, Regehr W, Harvey CD, Drugowitsch J, Ginty DD. Meissner corpuscles and their spatially intermingled afferents underlie gentle touch perception. Science 2020; 368:eabb2751. [PMID: 32554568 PMCID: PMC7354383 DOI: 10.1126/science.abb2751] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 04/28/2020] [Indexed: 12/12/2022]
Abstract
Meissner corpuscles are mechanosensory end organs that densely occupy mammalian glabrous skin. We generated mice that selectively lacked Meissner corpuscles and found them to be deficient in both perceiving the gentlest detectable forces acting on glabrous skin and fine sensorimotor control. We found that Meissner corpuscles are innervated by two mechanoreceptor subtypes that exhibit distinct responses to tactile stimuli. The anatomical receptive fields of these two mechanoreceptor subtypes homotypically tile glabrous skin in a manner that is offset with respect to one another. Electron microscopic analysis of the two Meissner afferents within the corpuscle supports a model in which the extent of lamellar cell wrappings of mechanoreceptor endings determines their force sensitivity thresholds and kinetic properties.
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Affiliation(s)
- Nicole L Neubarth
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Alan J Emanuel
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Yin Liu
- Department of Biochemistry, Stanford University, 279 Campus Drive, Stanford, CA 94305, USA
- Howard Hughes Medical Institute, Stanford University, 279 Campus Drive, Stanford, CA 94305, USA
| | - Mark W Springel
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Annie Handler
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Qiyu Zhang
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Brendan P Lehnert
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Chong Guo
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Lauren L Orefice
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Amira Abdelaziz
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Michelle M DeLisle
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Michael Iskols
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Julia Rhyins
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Soo J Kim
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Stuart J Cattel
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Wade Regehr
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Christopher D Harvey
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Jan Drugowitsch
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - David D Ginty
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA.
- Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
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22
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Budelli G, Ni L, Berciu C, van Giesen L, Knecht ZA, Chang EC, Kaminski B, Silbering AF, Samuel A, Klein M, Benton R, Nicastro D, Garrity PA. Ionotropic Receptors Specify the Morphogenesis of Phasic Sensors Controlling Rapid Thermal Preference in Drosophila. Neuron 2019; 101:738-747.e3. [PMID: 30654923 DOI: 10.1016/j.neuron.2018.12.022] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 11/07/2018] [Accepted: 12/17/2018] [Indexed: 12/26/2022]
Abstract
Thermosensation is critical for avoiding thermal extremes and regulating body temperature. While thermosensors activated by noxious temperatures respond to hot or cold, many innocuous thermosensors exhibit robust baseline activity and lack discrete temperature thresholds, suggesting they are not simply warm and cool detectors. Here, we investigate how the aristal Cold Cells encode innocuous temperatures in Drosophila. We find they are not cold sensors but cooling-activated and warming-inhibited phasic thermosensors that operate similarly at warm and cool temperatures; we propose renaming them "Cooling Cells." Unexpectedly, Cooling Cell thermosensing does not require the previously reported Brivido Transient Receptor Potential (TRP) channels. Instead, three Ionotropic Receptors (IRs), IR21a, IR25a, and IR93a, specify both the unique structure of Cooling Cell cilia endings and their thermosensitivity. Behaviorally, Cooling Cells promote both warm and cool avoidance. These findings reveal a morphogenetic role for IRs and demonstrate the central role of phasic thermosensing in innocuous thermosensation. VIDEO ABSTRACT.
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Affiliation(s)
- Gonzalo Budelli
- Volen Center for Complex Systems, Department of Biology, Brandeis University, Waltham, MA 02454, USA
| | - Lina Ni
- Volen Center for Complex Systems, Department of Biology, Brandeis University, Waltham, MA 02454, USA; School of Neuroscience, Virginia Tech, Blacksburg, VA 24061, USA
| | - Cristina Berciu
- Rosenstiel Basic Medical Sciences Research Center, Department of Biology, Brandeis University, Waltham, MA 02453, USA
| | - Lena van Giesen
- Volen Center for Complex Systems, Department of Biology, Brandeis University, Waltham, MA 02454, USA
| | - Zachary A Knecht
- Volen Center for Complex Systems, Department of Biology, Brandeis University, Waltham, MA 02454, USA
| | - Elaine C Chang
- Volen Center for Complex Systems, Department of Biology, Brandeis University, Waltham, MA 02454, USA
| | - Benjamin Kaminski
- Department of Physics, University of Miami, Coral Gables, FL 33146, USA
| | - Ana F Silbering
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Lausanne 1015, Switzerland
| | - Aravi Samuel
- Department of Physics and Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Mason Klein
- Department of Physics, University of Miami, Coral Gables, FL 33146, USA; Department of Physics and Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Richard Benton
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Lausanne 1015, Switzerland
| | - Daniela Nicastro
- Rosenstiel Basic Medical Sciences Research Center, Department of Biology, Brandeis University, Waltham, MA 02453, USA; Departments of Cell Biology and Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039, USA.
| | - Paul A Garrity
- Volen Center for Complex Systems, Department of Biology, Brandeis University, Waltham, MA 02454, USA.
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23
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Dong B, Vold S, Olvera-Jaramillo C, Chang H. Functional redundancy of frizzled 3 and frizzled 6 in planar cell polarity control of mouse hair follicles. Development 2018; 145:dev168468. [PMID: 30237242 PMCID: PMC10682934 DOI: 10.1242/dev.168468] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 09/05/2018] [Indexed: 12/14/2022]
Abstract
The orientation of mouse hair follicles is controlled by the planar cell polarity (PCP) pathway. Mutations in PCP genes result in two categories of hair mis-orientation phenotype: randomly oriented and vertically oriented to the skin surface. Here, we demonstrate that the randomly oriented hair phenotype observed in frizzled 6 (Fzd6) mutants results from a partial loss of the polarity, due to the functional redundancy of another closely related frizzled gene, Fzd3 Double knockout of Fzd3 and Fzd6 globally, or only in the skin, led to vertically oriented hair follicles and a total loss of anterior-posterior polarity. Furthermore, we provide evidence that, contrary to the prevailing model, asymmetrical localization of the Fzd6 protein is not observed in skin epithelial cells. Through transcriptome analyses and in vitro studies, we show collagen triple helix repeat containing 1 (Cthrc1) to be a potential downstream effector of Fzd6, but not of Fzd3. Cthrc1 binds directly to the extracellular domains of Fzd3 and Fzd6 to enhance the Wnt/PCP signaling. These results suggest that Fzd3 and Fzd6 play a redundant role in controlling the polarity of developing skin, but through non-identical mechanisms.
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Affiliation(s)
- Bo Dong
- Department of Dermatology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
- Program in Genetics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Samantha Vold
- Department of Dermatology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | | | - Hao Chang
- Department of Dermatology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
- Program in Genetics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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24
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Abstract
Nociception, the sensory mechanism that allows animals to sense and avoid potentially tissue-damaging stimuli, is critical for survival. This process relies on nociceptors, which are specialized neurons that detect and respond to potentially damaging forms of energy - heat, mechanical and chemical - in the environment. Nociceptors accomplish this task through the expression of molecules that function to detect and signal the presence of potential harm. Downstream of the nociceptive sensory input, the neural signals trigger protective (nocifensive) behaviors, and the sensory stimuli that reach the brain may be perceived as painful.
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25
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Ibrahim LA, Huang JJ, Wang SZ, Kim YJ, Zhang LI, Tao HW. Sparse Labeling and Neural Tracing in Brain Circuits by STARS Strategy: Revealing Morphological Development of Type II Spiral Ganglion Neurons. Cereb Cortex 2018; 31:5049854. [PMID: 29982390 DOI: 10.1093/cercor/bhy154] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Indexed: 11/12/2022] Open
Abstract
Elucidating axonal and dendritic projection patterns of individual neurons is a key for understanding the cytoarchitecture of neural circuits in the brain. This requires genetic approaches to achieve Golgi-like sparse labeling of desired types of neurons. Here, we explored a novel strategy of stochastic gene activation with regulated sparseness (STARS), in which the stochastic choice between 2 competing Cre-lox recombination events is controlled by varying the lox efficiency and cassette length. In a created STARS transgenic mouse crossed with various Cre driver lines, sparse neuronal labeling with a relatively uniform level of sparseness was achieved across different brain regions and cell types in both central and peripheral nervous systems. Tracing of individual type II peripheral auditory fibers revealed for the first time that they undergo experience-dependent developmental refinement, which is impaired by attenuating external sound input. Our results suggest that STARS strategy can be applied for circuit mapping and sparse gene manipulation.
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Affiliation(s)
- Leena A Ibrahim
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
- Neuroscience Graduate Program, University of Southern California, Los Angeles, CA, USA
| | - Junxiang J Huang
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
- Medical Biology Graduate Program, University of Southern California, Los Angeles, CA, USA
| | - Sheng-Zhi Wang
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Young J Kim
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
- Neuroscience Graduate Program, University of Southern California, Los Angeles, CA, USA
| | - L I Zhang
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - H W Tao
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
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26
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Abstract
The sensation of touch is mediated by mechanosensory neurons that are embedded in skin and relay signals from the periphery to the central nervous system. During embryogenesis, axons elongate from these neurons to make contact with the developing skin. Concurrently, the epithelium of skin transforms from a homogeneous tissue into a heterogeneous organ that is made up of distinct layers and microdomains. Throughout this process, each neuronal terminal must form connections with an appropriate skin region to serve its function. This Review presents current knowledge of the development of the sensory microdomains in mammalian skin and the mechanosensory neurons that innervate them.
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Affiliation(s)
- Blair A Jenkins
- Department of Physiology & Cellular Biophysics and Department of Dermatology, Columbia University in the City of New York, New York, NY 10032, USA
| | - Ellen A Lumpkin
- Department of Physiology & Cellular Biophysics and Department of Dermatology, Columbia University in the City of New York, New York, NY 10032, USA
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27
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Olson W, Abdus-Saboor I, Cui L, Burdge J, Raabe T, Ma M, Luo W. Sparse genetic tracing reveals regionally specific functional organization of mammalian nociceptors. eLife 2017; 6:29507. [PMID: 29022879 PMCID: PMC5648527 DOI: 10.7554/elife.29507] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Accepted: 10/11/2017] [Indexed: 12/31/2022] Open
Abstract
The human distal limbs have a high spatial acuity for noxious stimuli but a low density of pain-sensing neurites. To elucidate mechanisms underlying regional differences in processing nociception, we sparsely traced non-peptidergic nociceptors across the body using a newly generated MrgprdCreERT2 mouse line. We found that mouse plantar paw skin is also innervated by a low density of Mrgprd+ nociceptors, while individual arbors in different locations are comparable in size. Surprisingly, the central arbors of plantar paw and trunk innervating nociceptors have distinct morphologies in the spinal cord. This regional difference is well correlated with a heightened signal transmission for plantar paw circuits, as revealed by both spinal cord slice recordings and behavior assays. Taken together, our results elucidate a novel somatotopic functional organization of the mammalian pain system and suggest that regional central arbor structure could facilitate the “enlarged representation” of plantar paw regions in the CNS.
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Affiliation(s)
- William Olson
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
| | - Ishmail Abdus-Saboor
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
| | - Lian Cui
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
| | - Justin Burdge
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
| | - Tobias Raabe
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
| | - Minghong Ma
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
| | - Wenqin Luo
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
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28
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Ghitani N, Barik A, Szczot M, Thompson JH, Li C, Le Pichon CE, Krashes MJ, Chesler AT. Specialized Mechanosensory Nociceptors Mediating Rapid Responses to Hair Pull. Neuron 2017; 95:944-954.e4. [PMID: 28817806 DOI: 10.1016/j.neuron.2017.07.024] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 04/27/2017] [Accepted: 07/21/2017] [Indexed: 12/13/2022]
Abstract
The somatosensory system provides animals with the ability to detect, distinguish, and respond to diverse thermal, mechanical, and irritating stimuli. While there has been progress in defining classes of neurons underlying temperature sensation and gentle touch, less is known about the neurons specific for mechanical pain. Here, we use in vivo functional imaging to identify a class of cutaneous sensory neurons that are selectively activated by high-threshold mechanical stimulation (HTMRs). We show that their optogenetic excitation evokes rapid protective and avoidance behaviors. Unlike other nociceptors, these HTMRs are fast-conducting Aδ-fibers with highly specialized circumferential endings wrapping the base of individual hair follicles. Notably, we find that Aδ-HTMRs innervate unique but overlapping fields and can be activated by stimuli as precise as the pulling of a single hair. Together, the distinctive features of this class of Aδ-HTMRs appear optimized for accurate and rapid localization of mechanical pain. VIDEO ABSTRACT.
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Affiliation(s)
- Nima Ghitani
- National Center for Complementary and Integrative Health (NCCIH), National Institutes of Health (NIH), Bethesda MD, USA
| | - Arnab Barik
- National Center for Complementary and Integrative Health (NCCIH), National Institutes of Health (NIH), Bethesda MD, USA
| | - Marcin Szczot
- National Center for Complementary and Integrative Health (NCCIH), National Institutes of Health (NIH), Bethesda MD, USA
| | - James H Thompson
- National Center for Complementary and Integrative Health (NCCIH), National Institutes of Health (NIH), Bethesda MD, USA
| | - Chia Li
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH), Bethesda MD, USA
| | - Claire E Le Pichon
- National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda MD, USA
| | - Michael J Krashes
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH), Bethesda MD, USA
| | - Alexander T Chesler
- National Center for Complementary and Integrative Health (NCCIH), National Institutes of Health (NIH), Bethesda MD, USA.
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29
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Molecular codes for cell type specification in Brn3 retinal ganglion cells. Proc Natl Acad Sci U S A 2017; 114:E3974-E3983. [PMID: 28465430 DOI: 10.1073/pnas.1618551114] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Visual information is conveyed from the eye to the brain by distinct types of retinal ganglion cells (RGCs). It is largely unknown how RGCs acquire their defining morphological and physiological features and connect to upstream and downstream synaptic partners. The three Brn3/Pou4f transcription factors (TFs) participate in a combinatorial code for RGC type specification, but their exact molecular roles are still unclear. We use deep sequencing to define (i) transcriptomes of Brn3a- and/or Brn3b-positive RGCs, (ii) Brn3a- and/or Brn3b-dependent RGC transcripts, and (iii) transcriptomes of retinorecipient areas of the brain at developmental stages relevant for axon guidance, dendrite formation, and synaptogenesis. We reveal a combinatorial code of TFs, cell surface molecules, and determinants of neuronal morphology that is differentially expressed in specific RGC populations and selectively regulated by Brn3a and/or Brn3b. This comprehensive molecular code provides a basis for understanding neuronal cell type specification in RGCs.
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30
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Arcourt A, Gorham L, Dhandapani R, Prato V, Taberner FJ, Wende H, Gangadharan V, Birchmeier C, Heppenstall PA, Lechner SG. Touch Receptor-Derived Sensory Information Alleviates Acute Pain Signaling and Fine-Tunes Nociceptive Reflex Coordination. Neuron 2016; 93:179-193. [PMID: 27989460 DOI: 10.1016/j.neuron.2016.11.027] [Citation(s) in RCA: 147] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Revised: 08/01/2016] [Accepted: 11/07/2016] [Indexed: 11/25/2022]
Abstract
Painful mechanical stimuli activate multiple peripheral sensory afferent subtypes simultaneously, including nociceptors and low-threshold mechanoreceptors (LTMRs). Using an optogenetic approach, we demonstrate that LTMRs do not solely serve as touch receptors but also play an important role in acute pain signaling. We show that selective activation of neuropeptide Y receptor-2-expressing (Npy2r) myelinated A-fiber nociceptors evokes abnormally exacerbated pain, which is alleviated by concurrent activation of LTMRs in a frequency-dependent manner. We further show that spatial summation of single action potentials from multiple NPY2R-positive afferents is sufficient to trigger nocifensive paw withdrawal, but additional simultaneous sensory input from LTMRs is required for normal well-coordinated execution of this reflex. Thus, our results show that combinatorial coding of noxious and tactile sensory input is required for normal acute mechanical pain signaling. Additionally, we established a causal link between precisely defined neural activity in functionally identified sensory neuron subpopulations and nocifensive behavior and pain.
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Affiliation(s)
- Alice Arcourt
- Institute of Pharmacology, Heidelberg University, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany
| | - Louise Gorham
- Institute of Pharmacology, Heidelberg University, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany
| | | | - Vincenzo Prato
- Institute of Pharmacology, Heidelberg University, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany
| | - Francisco J Taberner
- Institute of Pharmacology, Heidelberg University, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany
| | - Hagen Wende
- Institute of Pharmacology, Heidelberg University, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany; Max-Delbrueck-Center (MDC) for Molecular Medicine, Robert-Roessle-Strasse 10, 13125 Berlin, Germany
| | - Vijayan Gangadharan
- Institute of Pharmacology, Heidelberg University, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany
| | - Carmen Birchmeier
- Max-Delbrueck-Center (MDC) for Molecular Medicine, Robert-Roessle-Strasse 10, 13125 Berlin, Germany
| | | | - Stefan G Lechner
- Institute of Pharmacology, Heidelberg University, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany.
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31
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Genetic Identification of an Expansive Mechanoreceptor Sensitive to Skin Stroking. Cell 2016; 163:1783-1795. [PMID: 26687362 DOI: 10.1016/j.cell.2015.11.060] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 11/12/2015] [Accepted: 11/23/2015] [Indexed: 01/15/2023]
Abstract
Touch perception begins with activation of low-threshold mechanoreceptors (LTMRs) in the periphery. LTMR terminals exhibit tremendous morphological heterogeneity that specifies their mechanical receptivity. In a survey of mammalian skin, we found a preponderance of neurofilament-heavy-chain(+) circumferential endings associated with hair follicles, prompting us to develop a genetic strategy to interrogate these neurons. Targeted in vivo recordings revealed them to be Aβ field-LTMRs, identified 50 years ago but largely elusive thereafter. Remarkably, while Aβ field-LTMRs are highly sensitive to gentle stroking of the skin, they are unresponsive to hair deflection, and they encode skin indentation in the noxious range across large, spotty receptive fields. Individual Aβ field-LTMRs form up to 180 circumferential endings, making them the most anatomically expansive LTMR identified to date. Thus, Aβ field-LTMRs are a major mammalian LTMR subtype that forms circumferential endings in hairy skin, and their sensitivity to gentle skin stroking arises through integration across many low-sensitivity circumferential endings.
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32
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Walsh CM, Bautista DM, Lumpkin EA. Mammalian touch catches up. Curr Opin Neurobiol 2015; 34:133-9. [PMID: 26100741 DOI: 10.1016/j.conb.2015.05.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 05/22/2015] [Indexed: 11/17/2022]
Abstract
An assortment of touch receptors innervate the skin and encode different tactile features of the environment. Compared with invertebrate touch and other sensory systems, our understanding of the molecular and cellular underpinnings of mammalian touch lags behind. Two recent breakthroughs have accelerated progress. First, an arsenal of cell-type-specific molecular markers allowed the functional and anatomical properties of sensory neurons to be matched, thereby unraveling a cellular code for touch. Such markers have also revealed key roles of non-neuronal cell types, such as Merkel cells and keratinocytes, in touch reception. Second, the discovery of Piezo genes as a new family of mechanically activated channels has fueled the discovery of molecular mechanisms that mediate and mechanotransduction in mammalian touch receptors.
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Affiliation(s)
- Carolyn M Walsh
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3200, USA
| | - Diana M Bautista
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3200, USA.
| | - Ellen A Lumpkin
- Department of Dermatology, Columbia University College of Physicians & Surgeons, New York, NY 10032, USA; Department of Physiology & Cellular Biophysics, Columbia University College of Physicians & Surgeons, New York, NY 10032, USA.
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33
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Abstract
Cellular debris created by developmental processes or injury must be cleared by phagocytic cells to maintain and repair tissues. Cutaneous injuries damage not only epidermal cells but also the axonal endings of somatosensory (touch-sensing) neurons, which must be repaired to restore the sensory function of the skin. Phagocytosis of neuronal debris is usually performed by macrophages or other blood-derived professional phagocytes, but we have found that epidermal cells phagocytose somatosensory axon debris in zebrafish. Live imaging revealed that epidermal cells rapidly internalize debris into dynamic phosphatidylinositol 3-monophosphate-positive phagosomes that mature into phagolysosomes using a pathway similar to that of professional phagocytes. Epidermal cells phagocytosed not only somatosensory axon debris but also debris created by injury to other peripheral axons that were mislocalized to the skin, neighboring skin cells, and macrophages. Together, these results identify vertebrate epidermal cells as broad-specificity phagocytes that likely contribute to neural repair and wound healing.
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34
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Taylor-Clark TE, Wu KY, Thompson JA, Yang K, Bahia PK, Ajmo JM. Thy1.2 YFP-16 transgenic mouse labels a subset of large-diameter sensory neurons that lack TRPV1 expression. PLoS One 2015; 10:e0119538. [PMID: 25746468 PMCID: PMC4351979 DOI: 10.1371/journal.pone.0119538] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Accepted: 01/21/2015] [Indexed: 11/18/2022] Open
Abstract
The Thy1.2 YFP-16 mouse expresses yellow fluorescent protein (YFP) in specific subsets of peripheral and central neurons. The original characterization of this model suggested that YFP was expressed in all sensory neurons, and this model has been subsequently used to study sensory nerve structure and function. Here, we have characterized the expression of YFP in the sensory ganglia (DRG, trigeminal and vagal) of the Thy1.2 YFP-16 mouse, using biochemical, functional and anatomical analyses. Despite previous reports, we found that YFP was only expressed in approximately half of DRG and trigeminal neurons and less than 10% of vagal neurons. YFP-expression was only found in medium and large-diameter neurons that expressed neurofilament but not TRPV1. YFP-expressing neurons failed to respond to selective agonists for TRPV1, P2X(2/3 and TRPM8 channels in Ca2+ imaging assays. Confocal analysis of glabrous skin, hairy skin of the back and ear and skeletal muscle indicated that YFP was expressed in some peripheral terminals with structures consistent with their presumed non-nociceptive nature. In summary, the Thy1.2 YFP-16 mouse expresses robust YFP expression in only a subset of sensory neurons. But this mouse model is not suitable for the study of nociceptive nerves or the function of such nerves in pain and neuropathies.
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Affiliation(s)
- Thomas E. Taylor-Clark
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
- * E-mail:
| | - Kevin Y. Wu
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Julie-Ann Thompson
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Kiseok Yang
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Parmvir K. Bahia
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Joanne M. Ajmo
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
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35
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François A, Schüetter N, Laffray S, Sanguesa J, Pizzoccaro A, Dubel S, Mantilleri A, Nargeot J, Noël J, Wood JN, Moqrich A, Pongs O, Bourinet E. The Low-Threshold Calcium Channel Cav3.2 Determines Low-Threshold Mechanoreceptor Function. Cell Rep 2015; 10:370-382. [PMID: 25600872 DOI: 10.1016/j.celrep.2014.12.042] [Citation(s) in RCA: 139] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 11/14/2014] [Accepted: 12/18/2014] [Indexed: 12/12/2022] Open
Abstract
The T-type calcium channel Cav3.2 emerges as a key regulator of sensory functions, but its expression pattern within primary afferent neurons and its contribution to modality-specific signaling remain obscure. Here, we elucidate this issue using a unique knockin/flox mouse strain wherein Cav3.2 is replaced by a functional Cav3.2-surface-ecliptic GFP fusion. We demonstrate that Cav3.2 is a selective marker of two major low-threshold mechanoreceptors (LTMRs), Aδ- and C-LTMRs, innervating the most abundant skin hair follicles. The presence of Cav3.2 along LTMR-fiber trajectories is consistent with critical roles at multiple sites, setting their strong excitability. Strikingly, the C-LTMR-specific knockout uncovers that Cav3.2 regulates light-touch perception and noxious mechanical cold and chemical sensations and is essential to build up that debilitates allodynic symptoms of neuropathic pain, a mechanism thought to be entirely A-LTMR specific. Collectively, our findings support a fundamental role for Cav3.2 in touch/pain pathophysiology, validating their critic pharmacological relevance to relieve mechanical and cold allodynia.
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Affiliation(s)
- Amaury François
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France; CNRS UMR5203, 34095 Montpellier, France; INSERM, U661, 34095 Montpellier, France; Université de Montpellier, 34095 Montpellier, France
| | - Niklas Schüetter
- Department of Physiology, University of Saarland, School of Medicine, Kirrberger Straße 1, 66424 Homburg, Germany
| | - Sophie Laffray
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France; CNRS UMR5203, 34095 Montpellier, France; INSERM, U661, 34095 Montpellier, France; Université de Montpellier, 34095 Montpellier, France
| | - Juan Sanguesa
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France; CNRS UMR5203, 34095 Montpellier, France; INSERM, U661, 34095 Montpellier, France; Université de Montpellier, 34095 Montpellier, France
| | - Anne Pizzoccaro
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France; CNRS UMR5203, 34095 Montpellier, France; INSERM, U661, 34095 Montpellier, France; Université de Montpellier, 34095 Montpellier, France
| | - Stefan Dubel
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France; CNRS UMR5203, 34095 Montpellier, France; INSERM, U661, 34095 Montpellier, France; Université de Montpellier, 34095 Montpellier, France
| | - Annabelle Mantilleri
- Aix-Marseille-Université, CNRS, Institut de Biologie du Développement de Marseille, UMR 7288, 13288 Marseille, France
| | - Joel Nargeot
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France; CNRS UMR5203, 34095 Montpellier, France; INSERM, U661, 34095 Montpellier, France; Université de Montpellier, 34095 Montpellier, France
| | - Jacques Noël
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France; Université de Nice Sophia Antipolis, Institut de Pharmacologie Moléculaire et Cellulaire, UMR7275 CNRS, 660 route des lucioles, 06560 Valbonne, France
| | - John N Wood
- Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK
| | - Aziz Moqrich
- Aix-Marseille-Université, CNRS, Institut de Biologie du Développement de Marseille, UMR 7288, 13288 Marseille, France
| | - Olaf Pongs
- Department of Physiology, University of Saarland, School of Medicine, Kirrberger Straße 1, 66424 Homburg, Germany
| | - Emmanuel Bourinet
- Laboratories of Excellence, Ion Channel Science and Therapeutics, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France; CNRS UMR5203, 34095 Montpellier, France; INSERM, U661, 34095 Montpellier, France; Université de Montpellier, 34095 Montpellier, France.
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36
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Boada MD, Gutierrez S, Aschenbrenner CA, Houle TT, Hayashida KI, Ririe DG, Eisenach JC. Nerve injury induces a new profile of tactile and mechanical nociceptor input from undamaged peripheral afferents. J Neurophysiol 2014; 113:100-9. [PMID: 25274350 DOI: 10.1152/jn.00506.2014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Chronic pain after nerve injury is often accompanied by hypersensitivity to mechanical stimuli, yet whether this reflects altered input, altered processing, or both remains unclear. Spinal nerve ligation or transection results in hypersensitivity to mechanical stimuli in skin innervated by adjacent dorsal root ganglia, but no previous study has quantified the changes in receptive field properties of these neurons in vivo. To address this, we recorded intracellularly from L4 dorsal root ganglion neurons of anesthetized young adult rats, 1 wk after L5 partial spinal nerve ligation (pSNL) or sham surgery. One week after pSNL, hindpaw mechanical withdrawal threshold in awake, freely behaving animals was decreased in the L4 distribution on the nerve-injured side compared with sham controls. Electrophysiology revealed that high-threshold mechanoreceptive cells of A-fiber conduction velocity in L4 were sensitized, with a seven-fold reduction in mechanical threshold, a seven-fold increase in receptive field area, and doubling of maximum instantaneous frequency in response to peripheral stimuli, accompanied by reductions in after-hyperpolarization amplitude and duration. Only a reduction in mechanical threshold (minimum von Frey hair producing neuronal activity) was observed in C-fiber conduction velocity high-threshold mechanoreceptive cells. In contrast, low-threshold mechanoreceptive cells were desensitized, with a 13-fold increase in mechanical threshold, a 60% reduction in receptive field area, and a 40% reduction in instantaneous frequency to stimulation. No spontaneous activity was observed in L4 ganglia, and the likelihood of recording from neurons without a mechanical receptive field was increased after pSNL. These data suggest massively altered input from undamaged sensory afferents innervating areas of hypersensitivity after nerve injury, with reduced tactile and increased nociceptive afferent response. These findings differ importantly from previous preclinical studies, but are consistent with clinical findings in most patients with chronic neuropathic pain.
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Affiliation(s)
- M Danilo Boada
- Department of Anesthesiology, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Silvia Gutierrez
- Department of Anesthesiology, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Carol A Aschenbrenner
- Department of Anesthesiology, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Timothy T Houle
- Department of Anesthesiology, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Ken-Ichiro Hayashida
- Department of Anesthesiology, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Douglas G Ririe
- Department of Anesthesiology, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - James C Eisenach
- Department of Anesthesiology, Wake Forest School of Medicine, Winston-Salem, North Carolina
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37
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Chang H, Wang Y, Wu H, Nathans J. Flat mount imaging of mouse skin and its application to the analysis of hair follicle patterning and sensory axon morphology. J Vis Exp 2014:e51749. [PMID: 24999071 DOI: 10.3791/51749] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Skin is a highly heterogeneous tissue. Intra-dermal structures include hair follicles, arrector pili muscles, epidermal specializations (such as Merkel cell clusters), sebaceous glands, nerves and nerve endings, and capillaries. The spatial arrangement of these structures is tightly controlled on a microscopic scale--as seen, for example, in the orderly arrangement of cell types within a single hair follicle--and on a macroscopic scale--as seen by the nearly identical orientations of thousands of hair follicles within a local region of skin. Visualizing these structures without physically sectioning the skin is possible because of the 2-dimensional geometry of this organ. In this protocol, we show that mouse skin can be dissected, fixed, permeabilized, stained, and clarified as an intact two dimensional object, a flat mount. The protocol allows for easy visualization of skin structures in their entirety through the full thickness of large areas of skin by optical sectioning and reconstruction. Images of these structures can also be integrated with information about position and orientation relative to the body axes.
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Affiliation(s)
- Hao Chang
- Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine;
| | - Yanshu Wang
- Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine
| | - Hao Wu
- Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine
| | - Jeremy Nathans
- Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine; Department of Neuroscience, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine; Department of Ophthalmology, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine;
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38
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Owens DM, Lumpkin EA. Diversification and specialization of touch receptors in skin. Cold Spring Harb Perspect Med 2014; 4:4/6/a013656. [PMID: 24890830 DOI: 10.1101/cshperspect.a013656] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Our skin is the furthest outpost of the nervous system and a primary sensor for harmful and innocuous external stimuli. As a multifunctional sensory organ, the skin manifests a diverse and highly specialized array of mechanosensitive neurons with complex terminals, or end organs, which are able to discriminate different sensory stimuli and encode this information for appropriate central processing. Historically, the basis for this diversity of sensory specializations has been poorly understood. In addition, the relationship between cutaneous mechanosensory afferents and resident skin cells, including keratinocytes, Merkel cells, and Schwann cells, during the development and function of tactile receptors has been poorly defined. In this article, we will discuss conserved tactile end organs in the epidermis and hair follicles, with a focus on recent advances in our understanding that have emerged from studies of mouse hairy skin.
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Affiliation(s)
- David M Owens
- Department of Dermatology, Columbia University College of Physicians and Surgeons, New York, New York 10032 Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York 10032
| | - Ellen A Lumpkin
- Department of Dermatology, Columbia University College of Physicians and Surgeons, New York, New York 10032 Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, New York 10032
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39
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Abstract
The basal forebrain cholinergic system modulates neuronal excitability and vascular tone throughout the cerebral cortex and hippocampus. This system is severely affected in Alzheimer's disease (AD), and drug treatment to enhance cholinergic signaling is widely used as symptomatic therapy in AD. Defining the full morphologies of individual basal forebrain cholinergic neurons has, until now, been technically beyond reach due to their large axon arbor sizes. Using genetically-directed sparse labeling, we have characterized the complete morphologies of basal forebrain cholinergic neurons in the mouse. Individual arbors were observed to span multiple cortical columns, and to have >1000 branch points and total axon lengths up to 50 cm. In an AD model, cholinergic axons were slowly lost and there was an accumulation of axon-derived material in discrete puncta. Calculations based on published morphometric data indicate that basal forebrain cholinergic neurons in humans have a mean axon length of ∼100 meters. DOI:http://dx.doi.org/10.7554/eLife.02444.001 The human brain is made up of roughly 80 to 100 billion neurons, organized into extensive networks. Each neuron consists of a number of components: a cell body, which contains the nucleus; numerous short protrusions from the cell body called dendrites; and a long thin structure called an axon that carries the electrical signals generated in the cell body and the dendrites to the next neuron in the network. One of the most studied networks in the human brain is the basal forebrain network, which is made up of large neurons that communicate with one another using a chemical transmitter called acetylcholine. This network has a key role in cognition, and its neurons are among the first to degenerate in Alzheimer's disease. However, relatively little is known about the structure of these ‘cholinergic’ neurons because their large size makes them difficult to study using standard techniques. Now, Wu et al. have visualized, for the first time, the complete 3D structure of cholinergic neurons in the mouse forebrain. The mice in question had been genetically modified so that only ten or so of their many thousands of cholinergic neurons expressed a distinctive ‘marker’ protein. This made it possible to distinguish these neurons from surrounding brain tissue in order to visualize their structures. The resulting pictures clearly illustrate the neurons' complexity, with individual axons in adult mice displaying up to 1000 branches. Measurements showed that each cholinergic axon in the mouse brain is roughly 30 centimeters long, even though the brain itself is less than 2 centimeters from front to back. Based on measurements by other researchers, Wu et al. calculated that the axons of single cholinergic neurons in the human brain are about 100 meters long on average. The extreme length and complex branching structure of cholinergic forebrain neurons helps to explain why each neuron is able to modulate the activity of many others in the network. It could also explain their vulnerability to degeneration, as the need to transport materials over such long distances may limit the ability of these neurons to respond to damage. DOI:http://dx.doi.org/10.7554/eLife.02444.002
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Affiliation(s)
- Hao Wu
- Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States
| | - John Williams
- Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States
| | - Jeremy Nathans
- Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, United States Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, United States Department of Opthalmology, Johns Hopkins University School of Medicine, Baltimore, United States
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40
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T-type calcium channels in chronic pain: mouse models and specific blockers. Pflugers Arch 2014; 466:707-17. [PMID: 24590509 DOI: 10.1007/s00424-014-1484-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Accepted: 02/13/2014] [Indexed: 02/01/2023]
Abstract
Pain is a quite frequent complaint accompanying numerous pathologies. Among these pathological cases, neuropathies are retrieved with identified etiologies (chemotherapies, diabetes, surgeries…) and also more diffuse syndromes such as fibromyalgia. More broadly, pain is one of the first consequences of the majority of inherited diseases. Despite its importance for the quality of life, current pain management is limited to drugs that are either old or with a limited efficacy or that possess a bad benefit/risk ratio. As no new pharmacological concept has led to new analgesics in the last decades, the discovery of medications is needed, and to this aim the identification of new druggable targets in pain transmission is a first step. Therefore, studies of ion channels in pain pathways are extremely active. This is particularly true with ion channels in peripheral sensory neurons in dorsal root ganglia (DRG) known now to express unique sets of these channels. Moreover, both spinal and supraspinal levels are clearly important in pain modulation. Among these ion channels, we and others revealed the important role of low voltage-gated calcium channels in cellular excitability in different steps of the pain pathways. These channels, by being activated nearby resting membrane potential have biophysical characteristics suited to facilitate action potential generation and rhythmicity. In this review, we will review the current knowledge on the role of these channels in the perception and modulation of pain.
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41
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Bourinet E, Altier C, Hildebrand ME, Trang T, Salter MW, Zamponi GW. Calcium-permeable ion channels in pain signaling. Physiol Rev 2014; 94:81-140. [PMID: 24382884 DOI: 10.1152/physrev.00023.2013] [Citation(s) in RCA: 208] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The detection and processing of painful stimuli in afferent sensory neurons is critically dependent on a wide range of different types of voltage- and ligand-gated ion channels, including sodium, calcium, and TRP channels, to name a few. The functions of these channels include the detection of mechanical and chemical insults, the generation of action potentials and regulation of neuronal firing patterns, the initiation of neurotransmitter release at dorsal horn synapses, and the ensuing activation of spinal cord neurons that project to pain centers in the brain. Long-term changes in ion channel expression and function are thought to contribute to chronic pain states. Many of the channels involved in the afferent pain pathway are permeable to calcium ions, suggesting a role in cell signaling beyond the mere generation of electrical activity. In this article, we provide a broad overview of different calcium-permeable ion channels in the afferent pain pathway and their role in pain pathophysiology.
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42
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Lesniak DR, Marshall KL, Wellnitz SA, Jenkins BA, Baba Y, Rasband MN, Gerling GJ, Lumpkin EA. Computation identifies structural features that govern neuronal firing properties in slowly adapting touch receptors. eLife 2014; 3:e01488. [PMID: 24448409 PMCID: PMC3896213 DOI: 10.7554/elife.01488] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Touch is encoded by cutaneous sensory neurons with diverse morphologies and physiological outputs. How neuronal architecture influences response properties is unknown. To elucidate the origin of firing patterns in branched mechanoreceptors, we combined neuroanatomy, electrophysiology and computation to analyze mouse slowly adapting type I (SAI) afferents. These vertebrate touch receptors, which innervate Merkel cells, encode shape and texture. SAI afferents displayed a high degree of variability in touch-evoked firing and peripheral anatomy. The functional consequence of differences in anatomical architecture was tested by constructing network models representing sequential steps of mechanosensory encoding: skin displacement at touch receptors, mechanotransduction and action-potential initiation. A systematic survey of arbor configurations predicted that the arrangement of mechanotransduction sites at heminodes is a key structural feature that accounts in part for an afferent’s firing properties. These findings identify an anatomical correlate and plausible mechanism to explain the driver effect first described by Adrian and Zotterman. DOI:http://dx.doi.org/10.7554/eLife.01488.001 Sensory receptors in the skin supply us with information about objects in the world around us, including their shape and texture. These receptors also detect pressure, temperature, and pain, enabling us to respond appropriately to stimuli that could be potentially harmful. The activation of a touch receptor—for example, due to the movement of a hair—causes ions to flow into the cell, changing the electric charge inside it. When the charge exceeds a threshold value, the cell fires action potentials, which travel along its axon to the central nervous system. The patterns of these action potentials from a population of touch receptors carry all the information about a touch stimulus to the brain. Different types of sensory receptors have unique anatomical structures and distinct signaling patterns; however, little is known about how the structures of sensory receptors influence action potential firing. Now Lesniak and Marshall et al. have revealed that structure determines function in a type of mammalian touch receptor called the slowly adapting type I receptor, which is concentrated in fingertips and other areas of high tactile acuity. With the aid of high-resolution microscopy, the complex branching structure of the receptor and its network of nerve endings were mapped in three dimensions. Experiments revealed highly variable structures and firing patterns between individual touch receptors, and computational modeling showed that changing either the number or the arrangement of receptor endings influenced the neuron’s firing properties. This is the first computational model that captures touch encoding by combining skin properties, sensory transduction, and spike initiation. As well as providing new information on how structure permits function, this work opens up new possibilities for exploring how the skin maintains its sensory capabilities during routine maintenance and after injury. DOI:http://dx.doi.org/10.7554/eLife.01488.002
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Affiliation(s)
- Daine R Lesniak
- Department of Systems and Information Engineering, University of Virginia, Charlottesville, United States
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43
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Sajic M, Mastrolia V, Lee CY, Trigo D, Sadeghian M, Mosley AJ, Gregson NA, Duchen MR, Smith KJ. Impulse conduction increases mitochondrial transport in adult mammalian peripheral nerves in vivo. PLoS Biol 2013; 11:e1001754. [PMID: 24391474 PMCID: PMC3876979 DOI: 10.1371/journal.pbio.1001754] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 11/18/2013] [Indexed: 11/19/2022] Open
Abstract
Matching energy supply and demand is critical in the bioenergetic homeostasis of all cells. This is a special problem in neurons where high levels of energy expenditure may occur at sites remote from the cell body, given the remarkable length of axons and enormous variability of impulse activity over time. Positioning mitochondria at areas with high energy requirements is an essential solution to this problem, but it is not known how this is related to impulse conduction in vivo. Therefore, to study mitochondrial trafficking along resting and electrically active adult axons in vivo, confocal imaging of saphenous nerves in anaesthetised mice was combined with electrical and pharmacological stimulation of myelinated and unmyelinated axons, respectively. We show that low frequency activity induced by electrical stimulation significantly increases anterograde and retrograde mitochondrial traffic in comparison with silent axons. Higher frequency conduction within a physiological range (50 Hz) dramatically further increased anterograde, but not retrograde, mitochondrial traffic, by rapidly increasing the number of mobile mitochondria and gradually increasing their velocity. Similarly, topical application of capsaicin to skin innervated by the saphenous nerve increased mitochondrial traffic in both myelinated and unmyelinated axons. In addition, stationary mitochondria in axons conducting at higher frequency become shorter, thus supplying additional mitochondria to the trafficking population, presumably through enhanced fission. Mitochondria recruited to the mobile population do not accumulate near Nodes of Ranvier, but continue to travel anterogradely. This pattern of mitochondrial redistribution suggests that the peripheral terminals of sensory axons represent sites of particularly high metabolic demand during physiological high frequency conduction. As the majority of mitochondrial biogenesis occurs at the cell body, increased anterograde mitochondrial traffic may represent a mechanism that ensures a uniform increase in mitochondrial density along the length of axons during high impulse load, supporting the increased metabolic demand imposed by sustained conduction.
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Affiliation(s)
- Marija Sajic
- Department of Neuroinflammation, University College London, Institute of Neurology, London, United Kingdom
- * E-mail:
| | - Vincenzo Mastrolia
- Department of Neuroinflammation, University College London, Institute of Neurology, London, United Kingdom
| | - Chao Yu Lee
- Department of Neuroinflammation, University College London, Institute of Neurology, London, United Kingdom
| | - Diogo Trigo
- Department of Neuroinflammation, University College London, Institute of Neurology, London, United Kingdom
| | - Mona Sadeghian
- Department of Neuroinflammation, University College London, Institute of Neurology, London, United Kingdom
| | - Angelina J. Mosley
- Department of Neuroinflammation, University College London, Institute of Neurology, London, United Kingdom
| | - Norman A. Gregson
- Department of Neuroinflammation, University College London, Institute of Neurology, London, United Kingdom
| | - Michael R. Duchen
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Kenneth J. Smith
- Department of Neuroinflammation, University College London, Institute of Neurology, London, United Kingdom
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44
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Abstract
The somatosensory system decodes a wide range of tactile stimuli and thus endows us with a remarkable capacity for object recognition, texture discrimination, sensory-motor feedback and social exchange. The first step leading to perception of innocuous touch is activation of cutaneous sensory neurons called low-threshold mechanoreceptors (LTMRs). Here, we review the properties and functions of LTMRs, emphasizing the unique tuning properties of LTMR subtypes and the organizational logic of their peripheral and central axonal projections. We discuss the spinal cord neurophysiological representation of complex mechanical forces acting upon the skin and current views of how tactile information is processed and conveyed from the spinal cord to the brain. An integrative model in which ensembles of impulses arising from physiologically distinct LTMRs are integrated and processed in somatotopically aligned mechanosensory columns of the spinal cord dorsal horn underlies the nervous system's enormous capacity for perceiving the richness of the tactile world.
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Affiliation(s)
- Victoria E Abraira
- The Solomon H. Snyder Department of Neuroscience, Howard Hughes Medical Institute, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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45
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Turner EE. Nerve endings reveal hidden diversity in the skin. eLife 2012; 1:e00352. [PMID: 23256044 PMCID: PMC3524793 DOI: 10.7554/elife.00352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Experiments on transgenic mice have revealed that the morphologies of sensory neurons in the skin of mice are more complex and diverse than expected.
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Affiliation(s)
- Eric E Turner
- is in the Center for Integrative Brain Research , Seattle Children's Research Institute , Seattle , USA
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