1
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Tong C, Moayedi Y, Lumpkin EA. Merkel cells and keratinocytes in oral mucosa are activated by mechanical stimulation. Physiol Rep 2024; 12:e15826. [PMID: 38246872 PMCID: PMC10800296 DOI: 10.14814/phy2.15826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 08/28/2023] [Indexed: 01/23/2024] Open
Abstract
The detection of mechanical qualities of foodstuffs is essential for nutrient acquisition, evaluation of food freshness, and bolus formation during mastication. However, the mechanisms through which mechanosensitive cells in the oral cavity transmit mechanical information from the periphery to the brain are not well defined. We hypothesized Merkel cells, which are epithelial mechanoreceptors and important for pressure and texture sensing in the skin, can be mechanically activated in the oral cavity. Using live-cell calcium imaging, we recorded Merkel cell activity in ex vivo gingival and palatal preparations from mice in response to mechanical stimulation. Merkel cells responded with distinct temporal patterns and activation thresholds in a region-specific manner, with Merkel cells in the hard palate having a higher mean activation threshold than those in the gingiva. Unexpectedly, we found that oral keratinocytes were also activated by mechanical stimulation, even in the absence of Merkel cells. This indicates that mechanical stimulation of oral mucosa independently activates at least two subpopulations of epithelial cells. Finally, we found that oral Merkel cells contribute to preference for consuming oily emulsion. To our knowledge, these data represent the first functional study of Merkel-cell physiology and its role in flavor detection in the oral cavity.
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Affiliation(s)
- Chi‐Kun Tong
- Department of Physiology and Cellular BiophysicsColumbia University Medical CenterNew YorkNew YorkUSA
| | - Yalda Moayedi
- Department of Physiology and Cellular BiophysicsColumbia University Medical CenterNew YorkNew YorkUSA
- Present address:
Departments of Neurology and Otolaryngology‐Head and Neck SurgeryColumbia UniversityNew YorkNYUSA
| | - Ellen A. Lumpkin
- Department of Physiology and Cellular BiophysicsColumbia University Medical CenterNew YorkNew YorkUSA
- Department of DermatologyColumbia University Medical CenterNew YorkNew YorkUSA
- Present address:
Department of Molecular and Cell BiologyHelen Wills Neuroscience Institute, University of California, BerkeleyBerkeleyCAUSA
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2
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Cole CL, Yu VX, Perry S, Seenauth A, Lumpkin EA, Troche MS, Pitman MJ, Moayedi Y. Healthy Human Laryngopharyngeal Sensory Innervation Density Correlates with Age. Laryngoscope 2023; 133:773-784. [PMID: 35841384 DOI: 10.1002/lary.30287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 05/23/2022] [Accepted: 06/16/2022] [Indexed: 11/08/2022]
Abstract
OBJECTIVE Somatosensory feedback from upper airway structures is essential for swallowing and airway defense but little is known about the identities and distributions of human upper airway neurons. Furthermore, whether sensory innervation modifies with aging is unknown. In this study, we quantify neuronal and chemosensory cell density in upper airway structures and correlate with age. METHODS Participants underwent biopsies from base of tongue, lateral and midline pharyngeal wall, epiglottis, and arytenoids (N = 25 13 female/12 male; 20-80 years, mean 51.4 years without clinical diagnosis of dysphagia or clinical indication for biopsy). Tissue sections were labeled with antibodies for all neurons, myelinated neurons, and chemosensory cells. Densities of lamina propria innervation, epithelial innervation, solitary chemosensory cells, and taste buds were calculated and correlated with age. RESULTS Arytenoid had the highest density of innervation and chemosensory cells across all measures compared to other sites. Taste buds were frequently observed in arytenoid and epiglottis. Base of tongue, lateral pharynx, and midline posterior pharynx had minimal innervation and few chemosensory cells. Epithelial innervation was present primarily in close proximity to chemosensory cells and taste buds. Overall innervation and myelinated fibers in the arytenoid lamina propria decline with aging. CONCLUSION Findings establish the architecture of healthy adult sensory innervation and demonstrate the varied distribution of laryngopharyngeal innervation, necessary steps toward understanding the sensory basis for swallowing and airway defense. We also document age-related decline in arytenoid innervation density. These findings suggest that sensory afferent denervation of the upper airway may be a contributing factor to presbyphagia. LEVEL OF EVIDENCE NA Laryngoscope, 133:773-784, 2023.
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Affiliation(s)
- Caroline L Cole
- Vagelos College of Physicians and Surgeons, Columbia University, New York, New York, USA
| | - Victoria X Yu
- Department of Otolaryngology-Head & Neck Surgery, Columbia University, New York, New York, USA
| | - Sarah Perry
- Laboratory for the Study of Upper Airway Dysfunction, Department of Biobehavioral Sciences, Teachers College, Columbia University, New York, New York, USA.,Department of Medicine, University of Otago, Christchurch, New Zealand.,The University of Canterbury Rose Center for Stroke Recovery & Research at St. George's Medical Center, Christchurch, New Zealand
| | - Anisa Seenauth
- Department of Neurology, Columbia University, New York, New York, USA
| | - Ellen A Lumpkin
- Department of Physiology and Cellular Biophysics, Columbia University, New York, New York, USA
| | - Michelle S Troche
- Laboratory for the Study of Upper Airway Dysfunction, Department of Biobehavioral Sciences, Teachers College, Columbia University, New York, New York, USA
| | - Michael J Pitman
- Department of Otolaryngology-Head & Neck Surgery, Columbia University, New York, New York, USA
| | - Yalda Moayedi
- Department of Otolaryngology-Head & Neck Surgery, Columbia University, New York, New York, USA.,Department of Neurology, Columbia University, New York, New York, USA.,Department of Physiology and Cellular Biophysics, Columbia University, New York, New York, USA
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3
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Moayedi Y, Xu S, Obayashi SK, Hoffman BU, Gerling GJ, Lumpkin EA. The cellular basis of mechanosensation in mammalian tongue. Cell Rep 2023; 42:112087. [PMID: 36763499 PMCID: PMC10409885 DOI: 10.1016/j.celrep.2023.112087] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 11/16/2022] [Accepted: 01/23/2023] [Indexed: 02/11/2023] Open
Abstract
Mechanosensory neurons that innervate the tongue provide essential information to guide feeding, speech, and social grooming. We use in vivo calcium imaging of mouse trigeminal ganglion neurons to identify functional groups of mechanosensory neurons innervating the anterior tongue. These sensory neurons respond to thermal and mechanical stimulation. Analysis of neuronal activity patterns reveal that most mechanosensory trigeminal neurons are tuned to detect moving stimuli across the tongue. Using an unbiased, multilayer hierarchical clustering approach to classify pressure-evoked activity based on temporal response dynamics, we identify five functional classes of mechanosensory neurons with distinct force-response relations and adaptation profiles. These populations are tuned to detect different features of touch. Molecular markers of functionally distinct clusters are identified by analyzing cluster representation in genetically marked neuronal subsets. Collectively, these studies provide a platform for defining the contributions of functionally distinct mechanosensory neurons to oral behaviors crucial for survival in mammals.
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Affiliation(s)
- Yalda Moayedi
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA; Department of Neurology, Columbia University, New York, NY 10032, USA; Department of Otolaryngology - Head & Neck Surgery, Columbia University, New York, NY 10032, USA
| | - Shan Xu
- School of Engineering and Applied Science, University of Virginia, Charlottesville, VA 22904, USA
| | - Sophie K Obayashi
- Department of Molecular & Cell Biology, Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Benjamin U Hoffman
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA
| | - Gregory J Gerling
- School of Engineering and Applied Science, University of Virginia, Charlottesville, VA 22904, USA.
| | - Ellen A Lumpkin
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA; Department of Molecular & Cell Biology, Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA.
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4
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Clary RC, Jenkins BA, Lumpkin EA. Spatiotemporal dynamics of sensory neuron and Merkel-cell remodeling are decoupled during epidermal homeostasis. bioRxiv 2023:2023.02.14.528558. [PMID: 36824872 PMCID: PMC9949164 DOI: 10.1101/2023.02.14.528558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
As the juncture between the body and environment, epithelia are both protective barriers and sensory interfaces that continually renew. To determine whether sensory neurons remodel to maintain homeostasis, we used in vivo two-photon imaging of somatosensory axons innervating Merkel cells in adult mouse skin. These touch receptors were highly plastic: 63% of Merkel cells and 89% of branches appeared, disappeared, grew, regressed and/or relocated over a month. Interestingly, Merkel-cell plasticity was synchronized across arbors during rapid epithelial turnover. When Merkel cells remodeled, the degree of plasticity between Merkel-cell clusters and their axons was well correlated. Moreover, branches were stabilized by Merkel-cell contacts. These findings highlight the role of epithelial-neural crosstalk in homeostatic remodeling. Conversely, axons were also dynamic when Merkel cells were stable, indicating that intrinsic neural mechanisms drive branch plasticity. Two terminal morphologies innervated Merkel cells: transient swellings called boutons, and stable cups termed kylikes. In Atoh1 knockout mice that lack Merkel cells, axons showed higher complexity than control mice, with exuberant branching and no kylikes. Thus, Merkel cells limit axonal branching and promote branch maturation. Together, these results reveal a previously unsuspected high degree of plasticity in somatosensory axons that is biased, but not solely dictated, by plasticity of target epithelial cells. This system provides a platform to identify intrinsic and extrinsic mechanisms that govern axonal patterning in epithelial homeostasis.
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5
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McIntyre S, Hauser SC, Kusztor A, Boehme R, Moungou A, Isager PM, Homman L, Novembre G, Nagi SS, Israr A, Lumpkin EA, Abnousi F, Gerling GJ, Olausson H. The Language of Social Touch Is Intuitive and Quantifiable. Psychol Sci 2022; 33:1477-1494. [PMID: 35942875 DOI: 10.1177/09567976211059801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Touch is a powerful communication tool, but we have a limited understanding of the role played by particular physical features of interpersonal touch communication. In this study, adults living in Sweden performed a task in which messages (attention, love, happiness, calming, sadness, and gratitude) were conveyed by a sender touching the forearm of a receiver, who interpreted the messages. Two experiments (N = 32, N = 20) showed that within close relationships, receivers could identify the intuitive touch expressions of the senders, and we characterized the physical features of the touches associated with successful communication. Facial expressions measured with electromyography varied by message but were uncorrelated with communication performance. We developed standardized touch expressions and quantified the physical features with 3D hand tracking. In two further experiments (N = 20, N = 16), these standardized expressions were conveyed by trained senders and were readily understood by strangers unacquainted with the senders. Thus, the possibility emerges of a standardized, intuitively understood language of social touch.
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Affiliation(s)
- Sarah McIntyre
- Center for Social and Affective Neuroscience, Department of Biomedical and Clinical Sciences, Linköping University
| | - Steven C Hauser
- School of Engineering and Applied Science, University of Virginia
| | - Anikó Kusztor
- Center for Social and Affective Neuroscience, Department of Biomedical and Clinical Sciences, Linköping University
| | - Rebecca Boehme
- Center for Social and Affective Neuroscience, Department of Biomedical and Clinical Sciences, Linköping University
| | - Athanasia Moungou
- Center for Social and Affective Neuroscience, Department of Biomedical and Clinical Sciences, Linköping University
| | - Peder Mortvedt Isager
- Center for Social and Affective Neuroscience, Department of Biomedical and Clinical Sciences, Linköping University
| | - Lina Homman
- Center for Social and Affective Neuroscience, Department of Biomedical and Clinical Sciences, Linköping University
| | - Giovanni Novembre
- Center for Social and Affective Neuroscience, Department of Biomedical and Clinical Sciences, Linköping University
| | - Saad S Nagi
- Center for Social and Affective Neuroscience, Department of Biomedical and Clinical Sciences, Linköping University
| | | | - Ellen A Lumpkin
- Department of Physiology and Cellular Biophysics, Columbia University
| | | | | | - Håkan Olausson
- Center for Social and Affective Neuroscience, Department of Biomedical and Clinical Sciences, Linköping University
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6
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Hoffman BU, Baba Y, Lee SA, Tong CK, Konofagou EE, Lumpkin EA. Focused ultrasound excites action potentials in mammalian peripheral neurons in part through the mechanically gated ion channel PIEZO2. Proc Natl Acad Sci U S A 2022; 119:e2115821119. [PMID: 35580186 PMCID: PMC9173751 DOI: 10.1073/pnas.2115821119] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2021] [Accepted: 03/29/2022] [Indexed: 11/19/2022] Open
Abstract
Neurons of the peripheral nervous system (PNS) are tasked with diverse roles, from encoding touch, pain, and itch to interoceptive control of inflammation and organ physiology. Thus, technologies that allow precise control of peripheral nerve activity have the potential to regulate a wide range of biological processes. Noninvasive modulation of neuronal activity is an important translational application of focused ultrasound (FUS). Recent studies have identified effective strategies to modulate brain circuits; however, reliable parameters to control the activity of the PNS are lacking. To develop robust noninvasive technologies for peripheral nerve modulation, we employed targeted FUS stimulation and electrophysiology in mouse ex vivo skin-saphenous nerve preparations to record the activity of individual mechanosensory neurons. Parameter space exploration showed that stimulating neuronal receptive fields with high-intensity, millisecond FUS pulses reliably and repeatedly evoked one-to-one action potentials in all peripheral neurons recorded. Interestingly, when neurons were classified based on neurophysiological properties, we identified a discrete range of FUS parameters capable of exciting all neuronal classes, including myelinated A fibers and unmyelinated C fibers. Peripheral neurons were excited by FUS stimulation targeted to either cutaneous receptive fields or peripheral nerves, a key finding that increases the therapeutic range of FUS-based peripheral neuromodulation. FUS elicited action potentials with millisecond latencies compared with electrical stimulation, suggesting ion channel–mediated mechanisms. Indeed, FUS thresholds were elevated in neurons lacking the mechanically gated channel PIEZO2. Together, these results demonstrate that transcutaneous FUS drives peripheral nerve activity by engaging intrinsic mechanotransduction mechanisms in neurons [B. U. Hoffman, PhD thesis, (2019)].
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Affiliation(s)
- Benjamin U. Hoffman
- Department of Physiology & Cellular Biophysics, Columbia University, New York, NY 10032
- Program in Neurobiology & Behavior, Columbia University, New York, NY 10032
- Department of Medicine, University of California, San Francisco, CA 94143
| | - Yoshichika Baba
- Department of Physiology & Cellular Biophysics, Columbia University, New York, NY 10032
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
| | - Stephen A. Lee
- Department of Biomedical Engineering, Columbia University, New York, NY 10032
| | - Chi-Kun Tong
- Department of Physiology & Cellular Biophysics, Columbia University, New York, NY 10032
| | - Elisa E. Konofagou
- Department of Biomedical Engineering, Columbia University, New York, NY 10032
| | - Ellen A. Lumpkin
- Department of Physiology & Cellular Biophysics, Columbia University, New York, NY 10032
- Program in Neurobiology & Behavior, Columbia University, New York, NY 10032
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
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7
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Guo Z, Tong C, Jacków J, Doucet YS, Abaci HE, Zeng W, Hansen C, Hayashi R, DeLorenzo D, Rami A, Pappalardo A, Lumpkin EA, Christiano AM. Engineering human skin model innervated with itch sensory neuron-like cells differentiated from induced pluripotent stem cells. Bioeng Transl Med 2022; 7:e10247. [PMID: 35111948 PMCID: PMC8780951 DOI: 10.1002/btm2.10247] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 07/30/2021] [Accepted: 08/01/2021] [Indexed: 12/15/2022] Open
Abstract
Atopic dermatitis (AD), driven by interleukins (IL-4/IL-13), is a chronic inflammatory skin disease characterized by intensive pruritus. However, it is unclear how immune signaling and sensory response pathways cross talk with each other. We differentiated itch sensory neuron-like cells (ISNLCs) from iPSC lines. These ISNLCs displayed neural markers and action potentials and responded specifically to itch-specific stimuli. These ISNLCs expressed receptors specific for IL-4/IL-13 and were activated directly by the two cytokines. We successfully innervated these ISNLCs into full thickness human skin constructs. These innervated skin grafts can be used in clinical applications such as wound healing. Moreover, the availability of such innervated skin models will be valuable to develop drugs to treat skin diseases such as AD.
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Affiliation(s)
- Zongyou Guo
- Department of DermatologyColumbia UniversityNew YorkNew YorkUSA
| | - Chi‐Kun Tong
- Department of DermatologyColumbia UniversityNew YorkNew YorkUSA
| | - Joanna Jacków
- Department of DermatologyColumbia UniversityNew YorkNew YorkUSA
| | - Yanne S. Doucet
- Department of DermatologyColumbia UniversityNew YorkNew YorkUSA
| | - Hasan E. Abaci
- Department of DermatologyColumbia UniversityNew YorkNew YorkUSA
| | - Wangyong Zeng
- Department of DermatologyColumbia UniversityNew YorkNew YorkUSA
| | - Corey Hansen
- Department of DermatologyColumbia UniversityNew YorkNew YorkUSA
| | - Ryota Hayashi
- Department of DermatologyColumbia UniversityNew YorkNew YorkUSA
| | | | - Avina Rami
- Department of DermatologyColumbia UniversityNew YorkNew YorkUSA
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8
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Moayedi Y, Michlig S, Park M, Koch A, Lumpkin EA. Somatosensory innervation of healthy human oral tissues. J Comp Neurol 2021; 529:3046-3061. [PMID: 33786834 PMCID: PMC10052750 DOI: 10.1002/cne.25148] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 03/17/2021] [Accepted: 03/19/2021] [Indexed: 12/15/2022]
Abstract
The oral somatosensory system relays essential information about mechanical stimuli to enable oral functions such as feeding and speech. The neurochemical and anatomical diversity of sensory neurons across oral cavity sites have not been systematically compared. To address this gap, we analyzed healthy human tongue and hard-palate innervation. Biopsies were collected from 12 volunteers and underwent fluorescent immunohistochemistry (≥2 specimens per marker/structure). Afferents were analyzed for markers of neurons (βIII tubulin), myelinated afferents (neurofilament heavy, NFH), and Merkel cells and taste cells (keratin 20, K20). Hard-palate innervation included Meissner corpuscles, glomerular endings, Merkel cell-neurite complexes, and free nerve endings. The organization of these somatosensory endings is reminiscent of fingertips, suggesting that the hard palate is equipped with a rich repertoire of sensory neurons for pressure sensing and spatial localization of mechanical inputs, which are essential for speech production and feeding. Likewise, the tongue is innervated by afferents that impart it with exquisite acuity and detection of moving stimuli that support flavor construction and speech. Filiform papillae contained end bulbs of Krause, as well as endings that have not been previously reported, including subepithelial neuronal densities, and NFH+ neurons innervating basal epithelia. Fungiform papillae had Meissner corpuscles and densities of NFH+ intraepithelial neurons surrounding taste buds. The differing compositions of sensory endings within filiform and fungiform papillae suggest that these structures have distinct roles in mechanosensation. Collectively, this study has identified previously undescribed neuronal endings in human oral tissues and provides an anatomical framework for understanding oral mechanosensory functions.
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Affiliation(s)
- Yalda Moayedi
- Department of Physiology and Cellular Biophysics, Columbia University, New York, New York, USA.,Department of Neurology, Columbia University, New York, New York, USA.,Department of Otolaryngology-Head and Neck Surgery, Columbia University, New York, New York, USA
| | | | - Mark Park
- Oral and Maxillofacial Surgery, New York Presbyterian, Columbia University, New York, New York, USA
| | - Alia Koch
- Oral and Maxillofacial Surgery, New York Presbyterian, Columbia University, New York, New York, USA
| | - Ellen A Lumpkin
- Department of Physiology and Cellular Biophysics, Columbia University, New York, New York, USA.,Department of Molecular and Cell Biology, Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, California, USA
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9
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Moayedi Y, Michlig S, Park M, Koch A, Lumpkin EA. Cover Image, Volume 529, Issue 11. J Comp Neurol 2021. [DOI: 10.1002/cne.25190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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10
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Jenkins BA, Fontecilla NM, Lu CP, Fuchs E, Lumpkin EA. The cellular basis of mechanosensory Merkel-cell innervation during development. eLife 2019; 8:42633. [PMID: 30794158 PMCID: PMC6386521 DOI: 10.7554/elife.42633] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 02/06/2019] [Indexed: 02/06/2023] Open
Abstract
Touch sensation is initiated by mechanosensory neurons that innervate distinct skin structures; however, little is known about how these neurons are patterned during mammalian skin development. We explored the cellular basis of touch-receptor patterning in mouse touch domes, which contain mechanosensory Merkel cell-neurite complexes and abut primary hair follicles. At embryonic stage 16.5 (E16.5), touch domes emerge as patches of Merkel cells and keratinocytes clustered with a previously unsuspected population of Bmp4-expressing dermal cells. Epidermal Noggin overexpression at E14.5 disrupted touch-dome formation but not hair-follicle specification, demonstrating a temporally distinct requirement for BMP signaling in placode-derived structures. Surprisingly, two neuronal populations preferentially targeted touch domes during development but only one persisted in mature touch domes. Finally, Keratin-17-expressing keratinocytes but not Merkel cells were necessary to establish innervation patterns during development. These findings identify key cell types and signaling pathways required for targeting Merkel-cell afferents to discrete mechanosensory compartments.
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Affiliation(s)
- Blair A Jenkins
- Department of Physiology and Cellular BiophysicsColumbia UniversityNew YorkUnited States
- Department of DermatologyColumbia UniversityNew YorkUnited States
| | - Natalia M Fontecilla
- Department of Physiology and Cellular BiophysicsColumbia UniversityNew YorkUnited States
| | - Catherine P Lu
- Robin Neustein Laboratory of Mammalian Development and Cell BiologyHoward Hughes Medical Institute, The Rockefeller UniversityNew YorkUnited States
| | - Elaine Fuchs
- Robin Neustein Laboratory of Mammalian Development and Cell BiologyHoward Hughes Medical Institute, The Rockefeller UniversityNew YorkUnited States
| | - Ellen A Lumpkin
- Department of Physiology and Cellular BiophysicsColumbia UniversityNew YorkUnited States
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11
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Moayedi Y, Greenberg SA, Jenkins BA, Marshall KL, Dimitrov LV, Nelson AM, Owens DM, Lumpkin EA. Camphor white oil induces tumor regression through cytotoxic T cell-dependent mechanisms. Mol Carcinog 2019; 58:722-734. [PMID: 30582219 DOI: 10.1002/mc.22965] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 12/18/2018] [Accepted: 12/20/2018] [Indexed: 12/11/2022]
Abstract
Bioactive derivatives from the camphor laurel tree, Cinnamomum camphora, are posited to exhibit chemopreventive properties but the efficacy and mechanism of these natural products are not fully understood. We tested an essential-oil derivative, camphor white oil (CWO), for anti-tumor activity in a mouse model of keratinocyte-derived skin cancer. Daily topical treatment with CWO induced dramatic regression of pre-malignant skin tumors and a two-fold reduction in cutaneous squamous cell carcinomas. We next investigated underlying cellular and molecular mechanisms. In cultured keratinocytes, CWO stimulated calcium signaling, resulting in calcineurin-dependent activation of nuclear factor of activated T cells (NFAT). In vivo, CWO induced transcriptional changes in immune-related genes identified by RNA-sequencing, resulting in cytotoxic T cell-dependent tumor regression. Finally, we identified chemical constituents of CWO that recapitulated effects of the admixture. Together, these studies identify T cell-mediated tumor regression as a mechanism through which a plant-derived essential oil diminishes established tumor burden.
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Affiliation(s)
- Yalda Moayedi
- Department of Physiology and Cellular Biophysics, Columbia University Irving Medical Center, New York, New York
| | - Sophie A Greenberg
- Department of Dermatology, Columbia University Irving Medical Center, New York, New York
| | - Blair A Jenkins
- Medical Scientist Training Program, Columbia University Irving Medical Center, New York, New York
| | - Kara L Marshall
- Department of Dermatology, Columbia University Irving Medical Center, New York, New York
| | - Lina V Dimitrov
- Program in Neuroscience and Behavior, Barnard College, Columbia University, New York, New York
| | - Aislyn M Nelson
- Department of Dermatology, Columbia University Irving Medical Center, New York, New York.,Department of Neuroscience, Baylor College of Medicine, Houston, Texas
| | - David M Owens
- Department of Dermatology, Columbia University Irving Medical Center, New York, New York.,Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, New York
| | - Ellen A Lumpkin
- Department of Physiology and Cellular Biophysics, Columbia University Irving Medical Center, New York, New York.,Department of Dermatology, Columbia University Irving Medical Center, New York, New York
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12
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Hoffman BU, Baba Y, Griffith TN, Mosharov EV, Woo SH, Roybal DD, Karsenty G, Patapoutian A, Sulzer D, Lumpkin EA. Merkel Cells Activate Sensory Neural Pathways through Adrenergic Synapses. Neuron 2018; 100:1401-1413.e6. [PMID: 30415995 DOI: 10.1016/j.neuron.2018.10.034] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 09/21/2018] [Accepted: 10/22/2018] [Indexed: 01/06/2023]
Abstract
Epithelial-neuronal signaling is essential for sensory encoding in touch, itch, and nociception; however, little is known about the release mechanisms and neurotransmitter receptors through which skin cells govern neuronal excitability. Merkel cells are mechanosensory epidermal cells that have long been proposed to activate neuronal afferents through chemical synaptic transmission. We employed a set of classical criteria for chemical neurotransmission as a framework to test this hypothesis. RNA sequencing of adult mouse Merkel cells demonstrated that they express presynaptic molecules and biosynthetic machinery for adrenergic transmission. Moreover, live-cell imaging directly demonstrated that Merkel cells mediate activity- and VMAT-dependent release of fluorescent catecholamine neurotransmitter analogs. Touch-evoked firing in Merkel-cell afferents was inhibited either by pre-synaptic silencing of SNARE-mediated vesicle release from Merkel cells or by neuronal deletion of β2-adrenergic receptors. Together, these results identify both pre- and postsynaptic mechanisms through which Merkel cells excite mechanosensory afferents to encode gentle touch. VIDEO ABSTRACT.
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Affiliation(s)
- Benjamin U Hoffman
- Department of Physiology & Cellular Biophysics, Columbia University, New York, NY, USA; Program in Neurobiology & Behavior, Columbia University, New York, NY, USA
| | - Yoshichika Baba
- Department of Physiology & Cellular Biophysics, Columbia University, New York, NY, USA
| | - Theanne N Griffith
- Department of Physiology & Cellular Biophysics, Columbia University, New York, NY, USA
| | - Eugene V Mosharov
- Departments of Psychiatry, Neurology, and Pharmacology, Columbia University: Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY, USA
| | - Seung-Hyun Woo
- The Scripps Research Institute & Howard Hughes Medical Institute, La Jolla, CA, USA
| | - Daniel D Roybal
- Pharmacology Graduate Program, Columbia University, New York, NY, USA
| | - Gerard Karsenty
- Department of Genetics and Development, Columbia University, New York, NY, USA
| | - Ardem Patapoutian
- The Scripps Research Institute & Howard Hughes Medical Institute, La Jolla, CA, USA
| | - David Sulzer
- Departments of Psychiatry, Neurology, and Pharmacology, Columbia University: Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY, USA
| | - Ellen A Lumpkin
- Department of Physiology & Cellular Biophysics, Columbia University, New York, NY, USA; Program in Neurobiology & Behavior, Columbia University, New York, NY, USA; Department of Dermatology, Columbia University, New York, NY, USA.
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13
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Affiliation(s)
- Benjamin U Hoffman
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA.,Medical Scientist Training Program, Columbia University, New York, NY 10032, USA
| | - Ellen A Lumpkin
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA. .,Department of Dermatology, Columbia University, New York, NY 10032, USA
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14
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Abstract
Oral mechanoreception is implicated in fundamental functions including speech, food intake and swallowing; yet, the neuroanatomical substrates that encode mechanical stimuli are not well understood. Tactile perception is initiated by intricate mechanosensitive machinery involving dedicated cells and neurons. This signal transduction setup is coupled with the topology and mechanical properties of surrounding epithelium, thereby providing a sensitive and accurate system to detect stress fluctuations from the external environment. We mapped the distribution of anatomically distinct neuronal endings in mouse oral cavity using transgenic reporters, molecular markers and quantitative histomorphometry. We found that the tongue is equipped with an array of putative mechanoreceptors that express the principal mechanosensory channel Piezo2, including end bulbs of Krause innervating individual filiform papillae and a novel class of neuronal fibers innervating the epithelium surrounding taste buds. The hard palate and gums are densely populated with three classes of sensory afferents organized in discrete patterns including Merkel cell-neurite complexes, Meissner's corpuscles and glomerular corpuscles. In aged mice, we find that palatal Merkel cells reduce in number at key time-points that correlate with impaired oral abilities, such as swallowing and mastication. Collectively, this work identifies the mechanosensory architecture of oral tissues involved in feeding.
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Affiliation(s)
- Yalda Moayedi
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, 10032, USA
| | - Lucia F Duenas-Bianchi
- SPURS Biomedical Research Program, Department of Physiology and Cellular Biophysics, Columbia University Medical Center, New York, NY, 10032, USA
| | - Ellen A Lumpkin
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, 10032, USA. .,Department of Dermatology, Columbia University, New York, NY, 10032, USA. .,Program in Neurobiology and Behavior, Columbia University, New York, NY, 10032, USA.
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15
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Hill RZ, Hoffman BU, Morita T, Campos SM, Lumpkin EA, Brem RB, Bautista DM. The signaling lipid sphingosine 1-phosphate regulates mechanical pain. eLife 2018; 7:e33285. [PMID: 29561262 PMCID: PMC5896955 DOI: 10.7554/elife.33285] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 03/14/2018] [Indexed: 12/20/2022] Open
Abstract
Somatosensory neurons mediate responses to diverse mechanical stimuli, from innocuous touch to noxious pain. While recent studies have identified distinct populations of A mechanonociceptors (AMs) that are required for mechanical pain, the molecular underpinnings of mechanonociception remain unknown. Here, we show that the bioactive lipid sphingosine 1-phosphate (S1P) and S1P Receptor 3 (S1PR3) are critical regulators of acute mechanonociception. Genetic or pharmacological ablation of S1PR3, or blockade of S1P production, significantly impaired the behavioral response to noxious mechanical stimuli, with no effect on responses to innocuous touch or thermal stimuli. These effects are mediated by fast-conducting A mechanonociceptors, which displayed a significant decrease in mechanosensitivity in S1PR3 mutant mice. We show that S1PR3 signaling tunes mechanonociceptor excitability via modulation of KCNQ2/3 channels. Our findings define a new role for S1PR3 in regulating neuronal excitability and establish the importance of S1P/S1PR3 signaling in the setting of mechanical pain thresholds.
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Affiliation(s)
- Rose Z Hill
- Department of Molecular and Cell BiologyUniversity of California, BerkeleyBerkeleyUnited States
| | - Benjamin U Hoffman
- Department of Physiology and Cellular BiophysicsColumbia University College of Physicians and SurgeonsNew YorkUnited States
- Medical Scientist Training ProgramColumbia UniversityNew YorkUnited States
| | - Takeshi Morita
- Department of Molecular and Cell BiologyUniversity of California, BerkeleyBerkeleyUnited States
| | | | - Ellen A Lumpkin
- Department of Physiology and Cellular BiophysicsColumbia University College of Physicians and SurgeonsNew YorkUnited States
- Neurobiology CourseMarine Biological LaboratoryWoods HoleUnited States
| | - Rachel B Brem
- Department of Plant and Microbial BiologyUniversity of California, BerkeleyBerkeleyUnited States
- Buck Institute for Research on AgingNovatoUnited States
| | - Diana M Bautista
- Department of Molecular and Cell BiologyUniversity of California, BerkeleyBerkeleyUnited States
- Neurobiology CourseMarine Biological LaboratoryWoods HoleUnited States
- Helen Wills Neuroscience InstituteUniversity of California, BerkeleyBerkeleyUnited States
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16
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Florez-Paz DM, Tong CK, Hoffman BU, Lee SA, Konofagou EE, Lumpkin EA. Focused Ultrasound Evoked Responses in Dorsal Root Ganglion Neurons (DRG) and HEK293 Cells. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.3627] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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17
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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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18
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Marshall KL, Clary RC, Baba Y, Orlowsky RL, Gerling GJ, Lumpkin EA. Touch Receptors Undergo Rapid Remodeling in Healthy Skin. Cell Rep 2017; 17:1719-1727. [PMID: 27829143 DOI: 10.1016/j.celrep.2016.10.034] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Revised: 09/21/2016] [Accepted: 10/12/2016] [Indexed: 11/24/2022] Open
Abstract
Sensory tissues exposed to the environment, such as skin, olfactory epithelia, and taste buds, continuously renew; therefore, peripheral neurons must have mechanisms to maintain appropriate innervation patterns. Although somatosensory neurons regenerate after injury, little is known about how these neurons cope with normal target organ changes. To elucidate neuronal plasticity in healthy skin, we analyzed the structure of Merkel-cell afferents, which are gentle touch receptors, during skin remodeling that accompanies mouse hair-follicle regeneration. The number of Merkel cells is reduced by 90% and axonal arbors are simplified during active hair growth. These structures rebound within just days. Computational modeling predicts that Merkel-cell changes are probabilistic, but myelinated branch stability depends on Merkel-cell inputs. Electrophysiology and behavior demonstrate that tactile responsiveness is less reliable during active growth than in resting skin. These results reveal that somatosensory neurons display structural plasticity at the cost of impairment in the reliability of encoding gentle touch.
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Affiliation(s)
- Kara L Marshall
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA; Integrated Training Program in Cellular, Molecular and Biomedical Sciences, Columbia University, New York, NY 10032, USA
| | - Rachel C Clary
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA; Neurobiology and Behavior Training Program, Columbia University, New York, NY 10032, USA
| | - Yoshichika Baba
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA
| | - Rachel L Orlowsky
- Department of Systems and Information Engineering, University of Virginia, Charlottesville, VA 22904, USA; Department of Biomedical Engineering, University of Virginia, Charlottesville, VA 22904, USA
| | - Gregory J Gerling
- Department of Systems and Information Engineering, University of Virginia, Charlottesville, VA 22904, USA; Department of Biomedical Engineering, University of Virginia, Charlottesville, VA 22904, USA
| | - Ellen A Lumpkin
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA; Integrated Training Program in Cellular, Molecular and Biomedical Sciences, Columbia University, New York, NY 10032, USA; Neurobiology and Behavior Training Program, Columbia University, New York, NY 10032, USA; Department of Dermatology, Columbia University, New York, NY 10032, USA.
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19
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Griffith TN, Marquina-Solis JE, Thompson AC, Jenkins BA, Lumpkin EA. The Vglut3 Icre ;Rosa26 Ai14 Mouse Model as a Tool for Studying TRPM8 + Sensory Neurons. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.2204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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20
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Wang Y, Baba Y, Lumpkin EA, Gerling GJ. Computational modeling indicates that surface pressure can be reliably conveyed to tactile receptors even amidst changes in skin mechanics. J Neurophysiol 2016; 116:218-28. [PMID: 27098029 PMCID: PMC4961760 DOI: 10.1152/jn.00624.2015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 04/18/2016] [Indexed: 12/21/2022] Open
Abstract
Distinct patterns in neuronal firing are observed between classes of cutaneous afferents. Such differences may be attributed to end-organ morphology, distinct ion-channel complements, and skin microstructure, among other factors. Even for just the slowly adapting type I afferent, the skin's mechanics for a particular specimen might impact the afferent's firing properties, especially given the thickness and elasticity of skin can change dramatically over just days. Here, we show computationally that the skin can reliably convey indentation magnitude, rate, and spatial geometry to the locations of tactile receptors even amid changes in skin's structure. Using finite element analysis and neural dynamics models, we considered the skin properties of six mice that span a representative cohort. Modeling the propagation of the surface stimulus to the interior of the skin demonstrated that there can be large variance in stresses and strains near the locations of tactile receptors, which can lead to large variance in static firing rate. However, variance is significantly reduced when the stimulus tip is controlled by surface pressure and compressive stress is measured near the end organs. This particular transformation affords the least variability in predicted firing rates compared with others derived from displacement, force, strain energy density, or compressive strain. Amid changing skin mechanics, stimulus control by surface pressure may be more naturalistic and optimal and underlie how animals actively explore the tactile environment.
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Affiliation(s)
- Yuxiang Wang
- Department of Systems and Information Engineering, University of Virginia, Charlottesville, Virginia; Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Virginia
| | - Yoshichika Baba
- Department of Dermatology, Columbia University College of Physicians & Surgeons, New York, New York; and
| | - Ellen A Lumpkin
- Department of Dermatology, Columbia University College of Physicians & Surgeons, New York, New York; and Department of Physiology & Cellular Biophysics, Columbia University College of Physicians & Surgeons, New York, New York
| | - Gregory J Gerling
- Department of Systems and Information Engineering, University of Virginia, Charlottesville, Virginia; Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia;
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21
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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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22
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Marshall KL, Chadha M, deSouza LA, Sterbing-D'Angelo SJ, Moss CF, Lumpkin EA. Somatosensory substrates of flight control in bats. Cell Rep 2015; 11:851-858. [PMID: 25937277 DOI: 10.1016/j.celrep.2015.04.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Revised: 03/11/2015] [Accepted: 03/29/2015] [Indexed: 10/23/2022] Open
Abstract
Flight maneuvers require rapid sensory integration to generate adaptive motor output. Bats achieve remarkable agility with modified forelimbs that serve as airfoils while retaining capacity for object manipulation. Wing sensory inputs provide behaviorally relevant information to guide flight; however, components of wing sensory-motor circuits have not been analyzed. Here, we elucidate the organization of wing innervation in an insectivore, the big brown bat, Eptesicus fuscus. We demonstrate that wing sensory innervation differs from other vertebrate forelimbs, revealing a peripheral basis for the atypical topographic organization reported for bat somatosensory nuclei. Furthermore, the wing is innervated by an unusual complement of sensory neurons poised to report airflow and touch. Finally, we report that cortical neurons encode tactile and airflow inputs with sparse activity patterns. Together, our findings identify neural substrates of somatosensation in the bat wing and imply that evolutionary pressures giving rise to mammalian flight led to unusual sensorimotor projections.
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Affiliation(s)
- Kara L Marshall
- Departments of Dermatology and Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA
| | - Mohit Chadha
- Program in Neuroscience and Cognitive Science, University of Maryland, College Park, MD 20742, USA; Department of Psychology, University of Maryland, College Park, MD 20742, USA
| | - Laura A deSouza
- Program in Neurobiology and Behavior, Columbia University, New York, NY 10032, USA
| | | | - Cynthia F Moss
- Program in Neuroscience and Cognitive Science, University of Maryland, College Park, MD 20742, USA; Department of Psychology, University of Maryland, College Park, MD 20742, USA; Institute for Systems Research, University of Maryland, College Park, MD 20742, USA.
| | - Ellen A Lumpkin
- Departments of Dermatology and Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA; Program in Neurobiology and Behavior, Columbia University, New York, NY 10032, USA.
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23
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Wang Y, Marshall KL, Baba Y, Lumpkin EA, Gerling GJ. Compressive viscoelasticity of freshly excised mouse skin is dependent on specimen thickness, strain level and rate. PLoS One 2015; 10:e0120897. [PMID: 25803703 PMCID: PMC4372409 DOI: 10.1371/journal.pone.0120897] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Accepted: 01/27/2015] [Indexed: 11/18/2022] Open
Abstract
Although the skin’s mechanical properties are well characterized in tension, little work has been done in compression. Here, the viscoelastic properties of a population of mouse skin specimens (139 samples from 36 mice, aged 5 to 34 weeks) were characterized upon varying specimen thickness, as well as strain level and rate. Over the population, we observed the skin’s viscoelasticity to be quite variable, yet found systematic correlation of residual stress ratio with skin thickness and strain, and of relaxation time constants with strain rates. In particular, as specimen thickness ranged from 211 to 671 μm, we observed significant variation in both quasi-linear viscoelasticity (QLV) parameters, the relaxation time constant (τ1 = 0.19 ± 0.10 s) and steady-state residual stress ratio (G∞ = 0.28 ± 0.13). Moreover, when τ1 was decoupled and fixed, we observed that G∞ positively correlated with skin thickness. Second, as steady-state stretch was increased (λ∞ from 0.22 to 0.81), we observed significant variation in both QLV parameters (τ1 = 0.26 ± 0.14 s, G∞ = 0.47 ± 0.17), and when τ1 was fixed, G∞ positively correlated with stretch level. Third, as strain rate was increased from 0.06 to 22.88 s−1, the median time constant τ1 varied from 1.90 to 0.31 s, and thereby negatively correlated with strain rate. These findings indicate that the natural range of specimen thickness, as well as experimental controls of compression level and rate, significantly influence measurements of skin viscoelasticity.
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Affiliation(s)
- Yuxiang Wang
- Department of Systems and Information Engineering, University of Virginia, 151 Engineers Way, Charlottesville, Virginia, 22903, United States of America
- Department of Mechanical and Aerospace Engineering, University of Virginia, 122 Engineers Way, Charlottesville, Virginia, 22903, United States of America
| | - Kara L. Marshall
- Department of Dermatology, Columbia University College of Physicians & Surgeons, 1150 St. Nicholas Ave., New York, New York, 10032, United States of America
| | - Yoshichika Baba
- Department of Dermatology, Columbia University College of Physicians & Surgeons, 1150 St. Nicholas Ave., New York, New York, 10032, United States of America
| | - Ellen A. Lumpkin
- Department of Dermatology, Columbia University College of Physicians & Surgeons, 1150 St. Nicholas Ave., New York, New York, 10032, United States of America
- Department of Physiology & Cellular Biophysics, Columbia University College of Physicians & Surgeons, 1150 St. Nicholas Ave., New York, New York, 10032, United States of America
| | - Gregory J. Gerling
- Department of Systems and Information Engineering, University of Virginia, 151 Engineers Way, Charlottesville, Virginia, 22903, United States of America
- Department of Biomedical Engineering, University of Virginia, 415 Lane Road, Charlottesville, Virginia, 22908, United States of America
- * E-mail:
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24
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Abstract
The Merkel cell-neurite complex is a unique vertebrate touch receptor comprising two distinct cell types in the skin. Its presence in touch-sensitive skin areas was recognized more than a century ago, but the functions of each cell type in sensory transduction have been unclear. Three recent studies demonstrate that Merkel cells are mechanosensitive cells that function in touch transduction via Piezo2. One study concludes that Merkel cells, rather than sensory neurons, are principal sites of mechanotransduction, whereas two other studies report that both Merkel cells and neurons encode mechanical inputs. Together, these studies settle a long-standing debate on whether or not Merkel cells are mechanosensory cells, and enable future investigations of how these skin cells communicate with neurons.
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Affiliation(s)
- Seung-Hyun Woo
- Howard Hughes Medical Institute, Molecular and Cellular Neuroscience, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Ellen A Lumpkin
- Departments of Dermatology & Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA.
| | - Ardem Patapoutian
- Howard Hughes Medical Institute, Molecular and Cellular Neuroscience, The Scripps Research Institute, La Jolla, CA 92037, USA.
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25
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Nakatani M, Maksimovic S, Baba Y, Lumpkin EA. Mechanotransduction in epidermal Merkel cells. Pflugers Arch 2014; 467:101-8. [PMID: 25053537 DOI: 10.1007/s00424-014-1569-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Accepted: 06/27/2014] [Indexed: 12/24/2022]
Abstract
The cellular and molecular basis of vertebrate touch reception remains least understood among the traditional five senses. Somatosensory afferents that innervate the skin encode distinct tactile qualities, such as flutter, slip, and pressure. Gentle touch is thought to be transduced by somatosensory afferents whose tactile end organs selectively filter mechanical stimuli. These tactile end organs comprise afferent terminals in association with non-neuronal cell types such as Merkel cells, keratinocytes, and Schwann cells. An open question is whether these non-neuronal cells serve primarily as passive mechanical filters or whether they actively participate in mechanosensory transduction. This question has been most extensively studied in Merkel cells, which are epidermal cells that complex with sensory afferents in regions of high tactile acuity such as fingertips, whisker follicles, and touch domes. Merkel cell-neurite complexes mediate slowly adapting type I (SAI) responses, which encode sustained pressure and represent object features with high fidelity. How Merkel cells contribute to unique SAI firing patterns has been debated for decades; however, three recent studies in rodent models provide some direct answers. First, whole-cell recordings demonstrate that Merkel cells are touch-sensitive cells with fast, mechanically activated currents that require Piezo2. Second, optogenetics and intact recordings show that Merkel cells mediate sustained SAI firing. Finally, loss-of-function studies in transgenic mouse models reveal that SAI afferents are also touch sensitive. Together, these studies identify molecular mechanisms of mechanotransduction in Merkel cells, reveal unexpected functions for these cells in touch, and support a revised, two-receptor site model of mechanosensory transduction.
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Affiliation(s)
- Masashi Nakatani
- Department of Dermatology, Columbia University, 1150 St. Nicholas Avenue, room 302B, New York, NY, 10032, USA
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26
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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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27
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Maksimovic S, Nakatani M, Baba Y, Nelson AM, Marshall KL, Wellnitz SA, Firozi P, Woo SH, Ranade S, Patapoutian A, Lumpkin EA. Epidermal Merkel cells are mechanosensory cells that tune mammalian touch receptors. Nature 2014; 509:617-21. [PMID: 24717432 PMCID: PMC4097312 DOI: 10.1038/nature13250] [Citation(s) in RCA: 347] [Impact Index Per Article: 34.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Accepted: 03/13/2014] [Indexed: 11/18/2022]
Abstract
Touch submodalities, such as flutter and pressure, are mediated by somatosensory afferents whose terminal specializations extract tactile features and encode them as action potential trains with unique activity patterns. Whether non-neuronal cells tune touch receptors through active or passive mechanisms is debated. Terminal specializations are thought to function as passive mechanical filters analogous to the cochlea's basilar membrane, which deconstructs complex sounds into tones that are transduced by mechanosensory hair cells. The model that cutaneous specializations are merely passive has been recently challenged because epidermal cells express sensory ion channels and neurotransmitters; however, direct evidence that epidermal cells excite tactile afferents is lacking. Epidermal Merkel cells display features of sensory receptor cells and make 'synapse-like' contacts with slowly adapting type I (SAI) afferents. These complexes, which encode spatial features such as edges and texture, localize to skin regions with high tactile acuity, including whisker follicles, fingertips and touch domes. Here we show that Merkel cells actively participate in touch reception in mice. Merkel cells display fast, touch-evoked mechanotransduction currents. Optogenetic approaches in intact skin show that Merkel cells are both necessary and sufficient for sustained action-potential firing in tactile afferents. Recordings from touch-dome afferents lacking Merkel cells demonstrate that Merkel cells confer high-frequency responses to dynamic stimuli and enable sustained firing. These data are the first, to our knowledge, to directly demonstrate a functional, excitatory connection between epidermal cells and sensory neurons. Together, these findings indicate that Merkel cells actively tune mechanosensory responses to facilitate high spatio-temporal acuity. Moreover, our results indicate a division of labour in the Merkel cell-neurite complex: Merkel cells signal static stimuli, such as pressure, whereas sensory afferents transduce dynamic stimuli, such as moving gratings. Thus, the Merkel cell-neurite complex is an unique sensory structure composed of two different receptor cell types specialized for distinct elements of discriminative touch.
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Affiliation(s)
| | - Masashi Nakatani
- Department of Dermatology, Columbia University, New York, NY 10032
- Graduate School of System Design and Management, Keio University, Yokohama, JP
| | - Yoshichika Baba
- Department of Dermatology, Columbia University, New York, NY 10032
| | - Aislyn M. Nelson
- Department of Dermatology, Columbia University, New York, NY 10032
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77006
| | - Kara L. Marshall
- Department of Dermatology, Columbia University, New York, NY 10032
| | - Scott A. Wellnitz
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77006
| | - Pervez Firozi
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77006
| | - Seung-Hyun Woo
- Howard Hughes Medical Institute, Molecular and Cellular Neuroscience, The Scripps Research Institute, La Jolla CA 92037 USA
| | - Sanjeev Ranade
- Howard Hughes Medical Institute, Molecular and Cellular Neuroscience, The Scripps Research Institute, La Jolla CA 92037 USA
| | - Ardem Patapoutian
- Howard Hughes Medical Institute, Molecular and Cellular Neuroscience, The Scripps Research Institute, La Jolla CA 92037 USA
- Genomic Institute of the Novartis Research Foundation, San Diego, CA 92121 USA
| | - Ellen A. Lumpkin
- Department of Dermatology, Columbia University, New York, NY 10032
- Program in Neurobiology & Behavior, Columbia University, New York, NY 10032
- Department of Physiology & Cellular Biophysics, Columbia University, New York, NY 10032 USA
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28
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Abstract
The skin is a dynamic organ whose complex material properties are capable of withstanding continuous mechanical stress while accommodating insults and organism growth. Moreover, synchronized hair cycles, comprising waves of hair growth, regression and rest, are accompanied by dramatic fluctuations in skin thickness in mice. Whether such structural changes alter skin mechanics is unknown. Mouse models are extensively used to study skin biology and pathophysiology, including aging, UV-induced skin damage and somatosensory signaling. As the skin serves a pivotal role in the transfer function from sensory stimuli to neuronal signaling, we sought to define the mechanical properties of mouse skin over a range of normal physiological states. Skin thickness, stiffness and modulus were quantitatively surveyed in adult, female mice (Mus musculus). These measures were analyzed under uniaxial compression, which is relevant for touch reception and compression injuries, rather than tension, which is typically used to analyze skin mechanics. Compression tests were performed with 105 full-thickness, freshly isolated specimens from the hairy skin of the hind limb. Physiological variables included body weight, hair-cycle stage, maturity level, skin site and individual animal differences. Skin thickness and stiffness were dominated by hair-cycle stage at young (6–10 weeks) and intermediate (13–19 weeks) adult ages but by body weight in mature mice (26–34 weeks). Interestingly, stiffness varied inversely with thickness so that hyperelastic modulus was consistent across hair-cycle stages and body weights. By contrast, the mechanics of hairy skin differs markedly with anatomical location. In particular, skin containing fascial structures such as nerves and blood vessels showed significantly greater modulus than adjacent sites. Collectively, this systematic survey indicates that, although its structure changes dramatically throughout adult life, mouse skin at a given location maintains a constant elastic modulus to compression throughout normal physiological stages.
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Affiliation(s)
- Yuxiang Wang
- Department of Systems and Information Engineering, University of Virginia, Charlottesville, Virginia, United States of America
| | - Kara L. Marshall
- Department of Dermatology, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
| | - Yoshichika Baba
- Department of Dermatology, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
| | - Gregory J. Gerling
- Department of Systems and Information Engineering, University of Virginia, Charlottesville, Virginia, United States of America
- * E-mail: (GJG); (EAL)
| | - Ellen A. Lumpkin
- Department of Dermatology, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
- Department of Physiology and Cellular Biophysics, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
- * E-mail: (GJG); (EAL)
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Maksimovic S, Baba Y, Lumpkin EA. Neurotransmitters and synaptic components in the Merkel cell-neurite complex, a gentle-touch receptor. Ann N Y Acad Sci 2013; 1279:13-21. [PMID: 23530998 DOI: 10.1111/nyas.12057] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Merkel cells are an enigmatic group of rare cells found in the skin of vertebrates. Most make contacts with somatosensory afferents to form Merkel cell-neurite complexes, which are gentle-touch receptors that initiate slowly adapting type I responses. The function of Merkel cells within the complex remains debated despite decades of research. Numerous anatomical studies demonstrate that Merkel cells form synaptic-like contacts with sensory afferent terminals. Moreover, recent molecular analysis reveals that Merkel cells express dozens of presynaptic molecules that are essential for synaptic vesicle release in neurons. Merkel cells also produce a host of neuroactive substances that can act as fast excitatory neurotransmitters or neuromodulators. Here, we review the major neurotransmitters found in Merkel cells and discuss these findings in relation to the potential function of Merkel cells in touch reception.
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Affiliation(s)
- Srdjan Maksimovic
- Department of Dermatology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
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31
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Wang Y, Marshall KL, Baba Y, Lumpkin EA, Gerling GJ. Natural Variation in Skin Thickness Argues for Mechanical Stimulus Control by Force Instead of Displacement. Joint Eurohaptics Conf Symp Haptic Interfaces Virtual Environ Teleoper Syst 2013; 2013:645-650. [PMID: 24500653 DOI: 10.1109/whc.2013.6548484] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The neural response to touch stimuli is influenced by skin properties as well as the delivery of stimuli. Here, we compare stimuli controlled by displacement and force, and analyze the impact on firing rates of slowly adapting type I afferents as skin thickness and elasticity change. Uniaxial compression tests were used to measure the mechanical properties of mouse hind limb skin (n=5), resulting in a range of skin thickness measurements (211.6-530.6 μm) and hyper- and visco-elastic properties (average coefficient of variation=0.27).Values were integrated to an axisymmetric finite element model using an Ogden strain energy function. This calculated the propagation of surface loads to tactile end-organ locations, where maximum compressive stress and its rate were sampled and linearly regressed to firing rate. For the observed range of skin thickness, firing response was predicted under both force and displacement control of a ramp-and-hold stimulus. Over the ramp phase of stimulation, the variance in predicted firing rate was higher under displacement than under force control (22.2versus 4.9 Hz) with a similar trend in the sustained phase of stimulation (4.6versus1.3Hz). Given that skin thickness varies significantly between specimens, for human skin perhaps seven more so than for mice, the use of force control is predicted to decrease experimental variance in neurophysiological and psychophysical responses.
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Affiliation(s)
- Yuxiang Wang
- Department of Systems and Information Engineering, University of Virginia
| | - Kara L Marshall
- Dept. of Dermatology, Columbia University College of Physicians & Surgeons
| | - Yoshichika Baba
- Dept. of Physiology & Cellular Biophysics, Columbia University College of Physicians & Surgeons
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Kim EK, Wellnitz SA, Bourdon SM, Lumpkin EA, Gerling GJ. Force sensor in simulated skin and neural model mimic tactile SAI afferent spiking response to ramp and hold stimuli. J Neuroeng Rehabil 2012; 9:45. [PMID: 22824523 PMCID: PMC3506479 DOI: 10.1186/1743-0003-9-45] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Accepted: 07/05/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The next generation of prosthetic limbs will restore sensory feedback to the nervous system by mimicking how skin mechanoreceptors, innervated by afferents, produce trains of action potentials in response to compressive stimuli. Prior work has addressed building sensors within skin substitutes for robotics, modeling skin mechanics and neural dynamics of mechanotransduction, and predicting response timing of action potentials for vibration. The effort here is unique because it accounts for skin elasticity by measuring force within simulated skin, utilizes few free model parameters for parsimony, and separates parameter fitting and model validation. Additionally, the ramp-and-hold, sustained stimuli used in this work capture the essential features of the everyday task of contacting and holding an object. METHODS This systems integration effort computationally replicates the neural firing behavior for a slowly adapting type I (SAI) afferent in its temporally varying response to both intensity and rate of indentation force by combining a physical force sensor, housed in a skin-like substrate, with a mathematical model of neuronal spiking, the leaky integrate-and-fire. Comparison experiments were then conducted using ramp-and-hold stimuli on both the spiking-sensor model and mouse SAI afferents. The model parameters were iteratively fit against recorded SAI interspike intervals (ISI) before validating the model to assess its performance. RESULTS Model-predicted spike firing compares favorably with that observed for single SAI afferents. As indentation magnitude increases (1.2, 1.3, to 1.4 mm), mean ISI decreases from 98.81 ± 24.73, 54.52 ± 6.94, to 41.11 ± 6.11 ms. Moreover, as rate of ramp-up increases, ISI during ramp-up decreases from 21.85 ± 5.33, 19.98 ± 3.10, to 15.42 ± 2.41 ms. Considering first spikes, the predicted latencies exhibited a decreasing trend as stimulus rate increased, as is observed in afferent recordings. Finally, the SAI afferent's characteristic response of producing irregular ISIs is shown to be controllable via manipulating the output filtering from the sensor or adding stochastic noise. CONCLUSIONS This integrated engineering approach extends prior works focused upon neural dynamics and vibration. Future efforts will perfect measures of performance, such as first spike latency and irregular ISIs, and link the generation of characteristic features within trains of action potentials with current pulse waveforms that stimulate single action potentials at the peripheral afferent.
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Affiliation(s)
- Elmer K Kim
- Department of Systems and Information Engineering, University of Virginia, Charlottesville, VA 22904, USA
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Bautista DM, Lumpkin EA. Perspectives on: information and coding in mammalian sensory physiology: probing mammalian touch transduction. ACTA ACUST UNITED AC 2012; 138:291-301. [PMID: 21875978 PMCID: PMC3171080 DOI: 10.1085/jgp.201110637] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Diana M Bautista
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
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Woo SH, Baba Y, Franco AM, Lumpkin EA, Owens DM. Excitatory glutamate is essential for development and maintenance of the piloneural mechanoreceptor. Development 2012; 139:740-8. [PMID: 22241839 DOI: 10.1242/dev.070847] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The piloneural collar in mammalian hairy skin comprises an intricate pattern of circumferential and longitudinal sensory afferents that innervate primary and secondary pelage hairs. The longitudinal afferents tightly associate with terminal Schwann cell processes to form encapsulated lanceolate nerve endings of rapidly adapting mechanoreceptors. The molecular basis for piloneural development, maintenance and function is poorly understood. Here, we show that Nefh-expressing glutamatergic neurons represent a major population of longitudinal and circumferential sensory afferents innervating the piloneural collar. Our findings using a VGLUT2 conditional-null mouse model indicate that glutamate is essential for innervation, patterning and differentiation of NMDAR(+) terminal Schwann cells during piloneural collar development. Similarly, treatment of adult mice with a selective NMDAR antagonist severely perturbed piloneural collar structure and reduced excitability of these mechanosensory neurons. Collectively, these results show that DRG-derived glutamate is essential for the proper development, maintenance and sensory function of the piloneural mechanoreceptor.
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Affiliation(s)
- Seung-Hyun Woo
- Department of Pathology, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA
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36
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Abstract
Multiple senses, including hearing, touch and osmotic regulation, require the ability to convert force into an electrical signal: A process called mechanotransduction. Mechanotransduction occurs through specialized proteins that open an ion channel pore in response to a mechanical stimulus. Many of these proteins remain unidentified in vertebrates, but known mechanotransduction channels in lower organisms provide clues into their identity and mechanism. Bacteria, fruit flies and nematodes have all been used to elucidate the molecules necessary for force transduction. This chapter discusses many different mechanical senses and takes an evolutionary approach to review the proteins responsible for mechanotransduction in various biological kingdoms.
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Affiliation(s)
- Kara L. Marshall
- Integrated Graduate Program in Cellular, Molecular, Structural and Genetic Studies, Columbia University College of Physicians & Surgeons, New York, NY 10032
| | - Ellen A. Lumpkin
- Departments of Dermatology and Physiology and Cellular Biophysics, Columbia University College of Physicians & Surgeons, New York, NY 10032
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Abstract
Degenerin/epithelial sodium channels (DEG/ENaCs) are luminaries of gentle touch in Caenorhabditis elegans. In this issue of Neuron, Geffeney et al. demonstrate that eponymous DEG-1 channels carry mechanotransduction currents in a polymodal neuron, where they act upstream of transient receptor potential (TRP) channels.
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Affiliation(s)
- Aislyn M Nelson
- Department of Dermatology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
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38
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Williams AL, Gerling GJ, Wellnitz SA, Bourdon SM, Lumpkin EA. Skin relaxation predicts neural firing rate adaptation in SAI touch receptors. Annu Int Conf IEEE Eng Med Biol Soc 2011; 2010:6678-81. [PMID: 21096074 DOI: 10.1109/iembs.2010.5626264] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
In response to ramp-and-hold indentation, the slowly-adapting type I (SAI) afferent exhibits an exponential decrease in its firing frequency during the hold phase. Such adaptation may be tied to skin relaxation but is neither well understood nor has it been quantitatively modeled. The specific hypothesis of this work is that skin relaxation is a primary contributor to observed changes in firing rate. Double exponential functions were fit to 21 responses from a mouse SAI afferent for both instantaneous firing rate and indenter tip force over time. The model was then generalized by using a linear transformation between fit parameters for force and firing rate data, allowing prediction of firing rates from force. The results show that the generalized model matches the recorded firing rate (R(2) = 0.65) equally well as fitting a doubleexponential function directly to firing rate (R(2) = 0.67) for a second dataset. When the procedure was repeated with two D-hair fibers, the generalized model matched the recorded firing rate (R(2) = 0.47) much more poorly compared to the fitted double-exponential function (R(2) = 0.89). Thus, firing rate adaptation in SAI responses can be predicted by skin relaxation, whereas this factor alone did not adequately describe adaptation in the D-hair.
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Affiliation(s)
- Aaron L Williams
- Department of Systems and Information Engineering (SIE), University of Virginia (U.Va.), Charlottesville, VA 22904, USA.
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39
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Abstract
The sense of touch detects forces that bombard the body's surface. In metazoans, an assortment of morphologically and functionally distinct mechanosensory cell types are tuned to selectively respond to diverse mechanical stimuli, such as vibration, stretch, and pressure. A comparative evolutionary approach across mechanosensory cell types and genetically tractable species is beginning to uncover the cellular logic of touch reception.
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Affiliation(s)
- Ellen A Lumpkin
- Department of Dermatology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
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40
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Abstract
Epithelial stem cells in adult mammalian skin are known to maintain epidermal, follicular and sebaceous lineages during homeostasis. Recently, Merkel cell mechanoreceptors were identified as a fourth lineage derived from the proliferative layer of murine skin epithelium; however, the location of the stem or progenitor population for Merkel cells remains unknown. Here, we have identified a previously undescribed population of epidermal progenitors that reside in the touch domes of hairy skin, termed touch dome progenitor cells (TDPCs). TDPCs are epithelial keratinocytes and are distinguished by their unique co-expression of α6 integrin, Sca1 and CD200 surface proteins. TDPCs exhibit bipotent progenitor behavior as they give rise to both squamous and neuroendocrine epidermal lineages, whereas the remainder of the α6(+) Sca1(+) CD200(-) epidermis does not give rise to Merkel cells. Finally, TDPCs possess a unique transcript profile that appears to be enforced by the juxtaposition of TDPCs with Merkel cells within the touch dome niche.
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Affiliation(s)
- Seung-Hyun Woo
- Department of Pathology, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA
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41
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Wellnitz SA, Lesniak DR, Gerling GJ, Lumpkin EA. The regularity of sustained firing reveals two populations of slowly adapting touch receptors in mouse hairy skin. J Neurophysiol 2010; 103:3378-88. [PMID: 20393068 DOI: 10.1152/jn.00810.2009] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Touch is initiated by diverse somatosensory afferents that innervate the skin. The ability to manipulate and classify receptor subtypes is prerequisite for elucidating sensory mechanisms. Merkel cell-neurite complexes, which distinguish shapes and textures, are experimentally tractable mammalian touch receptors that mediate slowly adapting type I (SAI) responses. The assessment of SAI function in mutant mice has been hindered because previous studies did not distinguish SAI responses from slowly adapting type II (SAII) responses, which are thought to arise from different end organs, such as Ruffini endings. Thus we sought methods to discriminate these afferent types. We developed an epidermis-up ex vivo skin-nerve chamber to record action potentials from afferents while imaging Merkel cells in intact receptive fields. Using model-based cluster analysis, we found that two types of slowly adapting receptors were readily distinguished based on the regularity of touch-evoked firing patterns. We identified these clusters as SAI (coefficient of variation = 0.78 +/- 0.09) and SAII responses (0.21 +/- 0.09). The identity of SAI afferents was confirmed by recording from transgenic mice with green fluorescent protein-expressing Merkel cells. SAI receptive fields always contained fluorescent Merkel cells (n = 10), whereas SAII receptive fields lacked these cells (n = 5). Consistent with reports from other vertebrates, mouse SAI and SAII responses arise from afferents exhibiting similar conduction velocities, receptive field sizes, mechanical thresholds, and firing rates. These results demonstrate that mice, like other vertebrates, have two classes of slowly adapting light-touch receptors, identify a simple method to distinguish these populations, and extend the utility of skin-nerve recordings for genetic dissection of touch receptor mechanisms.
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Affiliation(s)
- Scott A Wellnitz
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas, USA
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42
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Lesniak DR, Wellnitz SA, Gerling GJ, Lumpkin EA. Statistical analysis and modeling of variance in the SA-I mechanoreceptor response to sustained indentation. Annu Int Conf IEEE Eng Med Biol Soc 2010; 2009:6814-7. [PMID: 19964911 DOI: 10.1109/iembs.2009.5334487] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The slowly-adapting type I mechanoreceptor (SA-I) exhibits variability in its steady-state firing rate both within an afferent upon repeated stimulation and between afferents. Additionally, inter-spike intervals of the SA-I are extremely variable during this steady-state firing. While variability of the SA-I response has been noted previously, the work presented herein provides a finer analysis of the impact of force and fiber on the SA-I response. Specifically, we test two hypotheses, that 1) fiber-to-fiber variation will significantly impact firing rate over the range of applied forces, and that 2) fiber-to-fiber variation will significantly impact the coefficient of variation (CV) of inter-spike intervals over the range of applied forces. Utilizing an ex vivo skin nerve preparation in the mouse, experiments were conducted with six SA-I fibers from five mice, and with compressive stimuli with force magnitudes up to 9.59 mN. We found fiber to significantly impact both firing rate and CV. These findings motivated the construction of a generalized input (force)-output (firing rate) model composed of a baseline response profile and a multiplicative fiber sensitivity factor. This work will inform future efforts to attribute variability to differences in skin, neuron, and receptor properties, and will contribute to the understanding of how much variability is acceptable in systems designed to provide tactile feedback to the nervous system.
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Affiliation(s)
- Daine R Lesniak
- Department of Systems and Information Engineering, University of Virginia, Charlottesville, VA 22904, USA
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Kim EK, Gerling GJ, Wellnitz SA, Lumpkin EA. Using Force Sensors and Neural Models to Encode Tactile Stimuli as Spike-based Responses. Proc Symp Haptic Interface Virtual Env Teleoperator Syst 2010:195-198. [PMID: 21826287 DOI: 10.1109/haptic.2010.5444657] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Tactile sensors will augment the next generation of prosthetic limbs. However, currently available sensors do not produce biologically-compatible output. This work seeks to illustrate that a force sensor combined with a bi-phasic, neural spiking algorithm, or spiking-sensor, can produce spiking patterns similar to that of the slowly adapting type I (SAI) mechanoreceptor. Experiments were conducted where first spike latency and inter-spike interval, in response to a rapidly delivered (100 ms) sustained displacement (1.1, 1.3, 1.5 mm for 5 s), were compared between the spiking-sensor and SAI recording. The results indicated that the predicted spike times were similar, in magnitude and increasing linear trend, to those observed with the SAI. Over the three displacements, average dynamic ISIs were 7.3, 4.2, 3.8 ms for the spiking-sensor and 6.2, 6.9, 4.1 ms for the SAI, while average static ISIs were 69.0, 45.2, 35.1 ms and 159.9, 69.6, 38.8 ms. The predicted first spike latencies (74.3, 73.9, 96.3 ms) lagged in comparison to those observed for the SAI (26.8, 31.7, 28.8 ms), which may be due to both the different applied force ramp-ups and the SAI's exquisite dynamic sensitivity range and rapid response time.
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Affiliation(s)
- Elmer K Kim
- Department of Systems and Information Engineering, University of Virginia, Charlottesville, VA USA,
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Morrison KM, Miesegaes GR, Lumpkin EA, Maricich SM. Mammalian Merkel cells are descended from the epidermal lineage. Dev Biol 2009; 336:76-83. [PMID: 19782676 DOI: 10.1016/j.ydbio.2009.09.032] [Citation(s) in RCA: 140] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Revised: 09/18/2009] [Accepted: 09/21/2009] [Indexed: 11/16/2022]
Abstract
Merkel cells are specialized cells in the skin that are important for proper neural encoding of light touch stimuli. Conflicting evidence suggests that these cells are lineally descended from either the skin or the neural crest. To address this question, we used epidermal (Krt14(Cre)) and neural crest (Wnt1(Cre)) Cre-driver lines to conditionally delete Atoh1 specifically from the skin or neural crest lineages, respectively, of mice. Deletion of Atoh1 from the skin lineage resulted in loss of Merkel cells from all regions of the skin, while deletion from the neural crest lineage had no effect on this cell population. Thus, mammalian Merkel cells are derived from the skin lineage.
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Affiliation(s)
- Kristin M Morrison
- Department of Pediatrics, Case Western Reserve University, Cleveland, OH 44106, USA
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45
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Maricich SM, Wellnitz SA, Nelson AM, Lesniak DR, Gerling GJ, Lumpkin EA, Zoghbi HY. Merkel cells are essential for light-touch responses. Science 2009; 324:1580-2. [PMID: 19541997 PMCID: PMC2743005 DOI: 10.1126/science.1172890] [Citation(s) in RCA: 198] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The peripheral nervous system detects different somatosensory stimuli, including pain, temperature, and touch. Merkel cell-neurite complexes are touch receptors composed of sensory afferents and Merkel cells. The role that Merkel cells play in light-touch responses has been the center of controversy for over 100 years. We used Cre-loxP technology to conditionally delete the transcription factor Atoh1 from the body skin and foot pads of mice. Merkel cells are absent from these areas in Atoh1(CKO) animals. Ex vivo skin/nerve preparations from Atoh1(CKO) animals demonstrate complete loss of the characteristic neurophysiologic responses normally mediated by Merkel cell-neurite complexes. Merkel cells are, therefore, required for the proper encoding of Merkel receptor responses, suggesting that these cells form an indispensible part of the somatosensory system.
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Affiliation(s)
- Stephen M Maricich
- Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
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Abstract
Merkel cells are rare epidermal cells whose function in the skin is still debated. These cells localize to highly touch-sensitive areas of vertebrate epithelia, including palatine ridges, touch domes and finger tips. In most cases, Merkel cells complex with somatosensory afferents to form slowly adapting touch receptors; it is unclear, however, whether mechanosensory transduction occurs in the Merkel cell, the somatosensory afferent or both. Classic anatomical results suggests that Merkel cells are sensory cells that transduce mechanical stimuli and then communicate with sensory afferents via neurotransmission. This model is supported by recent molecular, immunohistochemical and physiological studies of Merkel cells in vitro and in intact tissues. For example, Merkel cells express essential components of presynaptic machinery, including molecules required for release of the excitatory neurotransmitter glutamate. Moreover, Merkel cells in vitro and in vivo are activated by mechanical stimuli, including hypotonic-induced cell swelling. Although these findings support the hypothesis that Merkel cells are sensory receptor cells, a definitive demonstration that Merkel cells are necessary and sufficient to transduce touch awaits future studies.
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Affiliation(s)
- Henry Haeberle
- Neuroscience Graduate Program, UCSF, Baylor College of Medicine, Houston TX 77030
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47
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Piskorowski R, Haeberle H, Panditrao MV, Lumpkin EA. Voltage-activated ion channels and Ca(2+)-induced Ca (2+) release shape Ca (2+) signaling in Merkel cells. Pflugers Arch 2008; 457:197-209. [PMID: 18415122 DOI: 10.1007/s00424-008-0496-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2007] [Revised: 03/03/2008] [Accepted: 03/13/2008] [Indexed: 12/24/2022]
Abstract
Ca(2+) signaling and neurotransmission modulate touch-evoked responses in Merkel cell-neurite complexes. To identify mechanisms governing these processes, we analyzed voltage-activated ion channels and Ca(2+) signaling in purified Merkel cells. Merkel cells in the intact skin were specifically labeled by antibodies against voltage-activated Ca(2+) channels (Ca(V)2.1) and voltage- and Ca(2+)-activated K(+) (BK(Ca)) channels. Voltage-clamp recordings revealed small Ca(2+) currents, which produced Ca(2+) transients that were amplified sevenfold by Ca(2+)-induced Ca(2+) release. Merkel cells' voltage-activated K(+) currents were carried predominantly by BK(Ca) channels with inactivating and non-inactivating components. Thus, Merkel cells, like hair cells, have functionally diverse BK(Ca) channels. Finally, blocking K(+) channels increased response magnitude and dramatically shortened Ca(2+) transients evoked by mechanical stimulation. Together, these results demonstrate that Ca(2+) signaling in Merkel cells is governed by the interplay of plasma membrane Ca(2+) channels, store release and K(+) channels, and they identify specific signaling mechanisms that may control touch sensitivity.
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Affiliation(s)
- Rebecca Piskorowski
- Department of Physiology, University of California, San Francisco, CA 94143, USA
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Haeberle H, Bryan LA, Vadakkan TJ, Dickinson ME, Lumpkin EA. Swelling-activated Ca2+ channels trigger Ca2+ signals in Merkel cells. PLoS One 2008; 3:e1750. [PMID: 18454189 PMCID: PMC2365925 DOI: 10.1371/journal.pone.0001750] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2007] [Accepted: 02/08/2008] [Indexed: 01/26/2023] Open
Abstract
Merkel cell-neurite complexes are highly sensitive touch receptors comprising epidermal Merkel cells and sensory afferents. Based on morphological and molecular studies, Merkel cells are proposed to be mechanosensory cells that signal afferents via neurotransmission; however, functional studies testing this hypothesis in intact skin have produced conflicting results. To test this model in a simplified system, we asked whether purified Merkel cells are directly activated by mechanical stimulation. Cell shape was manipulated with anisotonic solution changes and responses were monitored by Ca2+ imaging with fura-2. We found that hypotonic-induced cell swelling, but not hypertonic solutions, triggered cytoplasmic Ca2+ transients. Several lines of evidence indicate that these signals arise from swelling-activated Ca2+-permeable ion channels. First, transients were reversibly abolished by chelating extracellular Ca2+, demonstrating a requirement for Ca2+ influx across the plasma membrane. Second, Ca2+ transients were initially observed near the plasma membrane in cytoplasmic processes. Third, voltage-activated Ca2+ channel (VACC) antagonists reduced transients by half, suggesting that swelling-activated channels depolarize plasma membranes to activate VACCs. Finally, emptying internal Ca2+ stores attenuated transients by 80%, suggesting Ca2+ release from stores augments swelling-activated Ca2+ signals. To identify candidate mechanotransduction channels, we used RT-PCR to amplify ion-channel transcripts whose pharmacological profiles matched those of hypotonic-evoked Ca2+ signals in Merkel cells. We found 11 amplicons, including PKD1, PKD2, and TRPC1, channels previously implicated in mechanotransduction in other cells. Collectively, these results directly demonstrate that Merkel cells are activated by hypotonic-evoked swelling, identify cellular signaling mechanisms that mediate these responses, and support the hypothesis that Merkel cells contribute to touch reception in the Merkel cell-neurite complex.
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Affiliation(s)
- Henry Haeberle
- Neuroscience Graduate Program, University of California San Francisco, San Francisco, California, United States of America
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas, United States of America
| | - Leigh A. Bryan
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas, United States of America
| | - Tegy J. Vadakkan
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Mary E. Dickinson
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Ellen A. Lumpkin
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- * E-mail:
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Abstract
Sensory neurons innervating the skin encode the familiar sensations of temperature, touch and pain. An explosion of progress has revealed unanticipated cellular and molecular complexity in these senses. It is now clear that perception of a single stimulus, such as heat, requires several transduction mechanisms. Conversely, a given protein may contribute to multiple senses, such as heat and touch. Recent studies have also led to the surprising insight that skin cells might transduce temperature and touch. To break the code underlying somatosensation, we must therefore understand how the skin's sensory functions are divided among signalling molecules and cell types.
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Affiliation(s)
- Ellen A Lumpkin
- Departments of Neuroscience, Molecular Physiology & Biophysics and Molecular & Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA
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Siemens J, Zhou S, Piskorowski R, Nikai T, Lumpkin EA, Basbaum AI, King D, Julius D. Spider toxins activate the capsaicin receptor to produce inflammatory pain. Nature 2006; 444:208-12. [PMID: 17093448 DOI: 10.1038/nature05285] [Citation(s) in RCA: 224] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2006] [Accepted: 09/27/2006] [Indexed: 11/09/2022]
Abstract
Bites and stings from venomous creatures can produce pain and inflammation as part of their defensive strategy to ward off predators or competitors. Molecules accounting for lethal effects of venoms have been extensively characterized, but less is known about the mechanisms by which they produce pain. Venoms from spiders, snakes, cone snails or scorpions contain a pharmacopoeia of peptide toxins that block receptor or channel activation as a means of producing shock, paralysis or death. We examined whether these venoms also contain toxins that activate (rather than inhibit) excitatory channels on somatosensory neurons to produce a noxious sensation in mammals. Here we show that venom from a tarantula that is native to the West Indies contains three inhibitor cysteine knot (ICK) peptides that target the capsaicin receptor (TRPV1), an excitatory channel expressed by sensory neurons of the pain pathway. In contrast with the predominant role of ICK toxins as channel inhibitors, these previously unknown 'vanillotoxins' function as TRPV1 agonists, providing new tools for understanding mechanisms of TRP channel gating. Some vanillotoxins also inhibit voltage-gated potassium channels, supporting potential similarities between TRP and voltage-gated channel structures. TRP channels can now be included among the targets of peptide toxins, showing that animals, like plants (for example, chilli peppers), avert predators by activating TRP channels on sensory nerve fibres to elicit pain and inflammation.
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Affiliation(s)
- Jan Siemens
- Department of Cellular and Molecular Pharmacology, University of California-San Francisco, 600 16th Street, San Francisco, California 94143-2140, USA
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