1
|
Peterman E, Quitevis EJA, Black EC, Horton EC, Aelmore RL, White E, Sagasti A, Rasmussen JP. Zebrafish cutaneous injury models reveal Langerhans cells engulf axonal debris in adult epidermis. Dis Model Mech 2023; 16:297033. [PMID: 36876992 PMCID: PMC10110399 DOI: 10.1242/dmm.049911] [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: 09/29/2022] [Accepted: 02/28/2023] [Indexed: 03/07/2023] Open
Abstract
Somatosensory neurons extend enormous peripheral axons to the skin, where they detect diverse environmental stimuli. Somatosensory peripheral axons are easily damaged due to their small caliber and superficial location. Axonal damage results in Wallerian degeneration, creating vast quantities of cellular debris that phagocytes must remove to maintain organ homeostasis. The cellular mechanisms that ensure efficient clearance of axon debris from stratified adult skin are unknown. Here, we establish zebrafish scales as a tractable model to study axon degeneration in the adult epidermis. Using this system, we demonstrate that skin-resident immune cells known as Langerhans cells engulf the majority of axon debris. In contrast to immature skin, adult keratinocytes do not significantly contribute to debris removal, even in animals lacking Langerhans cells. Our study establishes a powerful new model for studying Wallerian degeneration and identifies a new function for Langerhans cells in maintenance of adult skin homeostasis following injury. These findings have important implications for pathologies that trigger somatosensory axon degeneration.
Collapse
Affiliation(s)
- Eric Peterman
- Department of Biology, University of Washington, Seattle, WA, 98195, USA
| | | | - Erik C Black
- Department of Biology, University of Washington, Seattle, WA, 98195, USA.,Molecular and Cellular Biology Program, University of Washington, Seattle, WA, 98195, USA
| | - Emma C Horton
- Department of Biology, University of Washington, Seattle, WA, 98195, USA
| | - Rune L Aelmore
- Department of Biology, University of Washington, Seattle, WA, 98195, USA
| | - Ethan White
- Department of Biology, University of Washington, Seattle, WA, 98195, USA
| | - Alvaro Sagasti
- Molecular, Cell and Developmental Biology Department and Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA
| | - Jeffrey P Rasmussen
- Department of Biology, University of Washington, Seattle, WA, 98195, USA.,Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA, 98109, USA
| |
Collapse
|
2
|
Adula KP, Sagasti A. Live Imaging of Axonal Dynamics After Laser Axotomy of Peripheral Neurons in Zebrafish. Methods Mol Biol 2023; 2636:247-261. [PMID: 36881305 DOI: 10.1007/978-1-0716-3012-9_14] [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] [Indexed: 03/08/2023]
Abstract
Axon severing results in diverse outcomes, including successful regeneration and reestablishment of function, failure to regenerate, or neuronal cell death. Experimentally injuring an axon makes it possible to study degeneration of the distal stump that was detached from the cell body and document the successive steps of regeneration. Precise injury reduces damage to the environment surrounding an axon, and thereby the involvement of extrinsic processes, such as scarring or inflammation, enabling researchers to isolate the role that intrinsic factors play in regeneration. Several methods have been used to sever axons, each with advantages and disadvantages. This chapter describes using a laser on a two-photon microscope to cut individual axons of touch-sensing neurons in zebrafish larvae, and live confocal imaging to monitor its regeneration, a method that provides exceptional resolution.
Collapse
Affiliation(s)
- Kadidia P Adula
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, CA, USA
| | - Alvaro Sagasti
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, CA, USA.
| |
Collapse
|
3
|
Rosa JB, Nassman KY, Sagasti A. Sensory axons induce epithelial lipid microdomain remodeling and determine the distribution of junctions in the epidermis. Mol Biol Cell 2023; 34:ar5. [PMID: 36322392 PMCID: PMC9816649 DOI: 10.1091/mbc.e22-09-0396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [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: 09/06/2022] [Revised: 10/21/2022] [Accepted: 10/25/2022] [Indexed: 12/23/2022] Open
Abstract
Epithelial cell properties are determined by the polarized distribution of membrane lipids, the cytoskeleton, and adhesive junctions. Epithelia are often profusely innervated, but little work has addressed how neurites affect epithelial organization. We previously found that basal keratinocytes in the zebrafish epidermis enclose axons in ensheathment channels sealed by autotypic junctions. Here we characterized how axons remodel cell membranes, the cytoskeleton, and junctions in basal keratinocytes. At the apical surface of basal keratinocytes, axons organized lipid microdomains quantitatively enriched in reporters for PI(4,5)P2 and liquid-ordered (Lo) membranes. Lipid microdomains supported the formation of cadherin-enriched, F-actin protrusions, which wrapped around axons, likely initiating ensheathment. In the absence of axons, cadherin-enriched microdomains formed on basal cells but did not organize into contiguous domains. Instead, these isolated domains formed heterotypic junctions with periderm cells, a distinct epithelial cell type. Thus, axon endings dramatically remodel polarized epithelial components and regulate epidermal adhesion.
Collapse
Affiliation(s)
- Jeffrey B. Rosa
- Department of Molecular, Cell and Developmental Biology and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
| | - Khaled Y. Nassman
- Department of Molecular, Cell and Developmental Biology and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
| | - Alvaro Sagasti
- Department of Molecular, Cell and Developmental Biology and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
| |
Collapse
|
4
|
Adula KP, Shorey M, Chauhan V, Nassman K, Chen SF, Rolls MM, Sagasti A. The MAP3Ks DLK and LZK Direct Diverse Responses to Axon Damage in Zebrafish Peripheral Neurons. J Neurosci 2022; 42:6195-6210. [PMID: 35840323 PMCID: PMC9374156 DOI: 10.1523/jneurosci.1395-21.2022] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [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: 07/06/2021] [Revised: 06/14/2022] [Accepted: 06/27/2022] [Indexed: 11/21/2022] Open
Abstract
Mitogen-activated protein kinase kinase kinases (MAP3Ks) dual leucine kinase (DLK) and leucine zipper kinase (LZK) are essential mediators of axon damage responses, but their responses are varied, complex, and incompletely understood. To characterize their functions in axon injury, we generated zebrafish mutants of each gene, labeled motor neurons (MNs) and touch-sensing neurons in live zebrafish, precisely cut their axons with a laser, and assessed the ability of mutant axons to regenerate in larvae, before sex is apparent in zebrafish. DLK and LZK were required redundantly and cell autonomously for axon regeneration in MNs but not in larval Rohon-Beard (RB) or adult dorsal root ganglion (DRG) sensory neurons. Surprisingly, in dlk lzk double mutants, the spared branches of wounded RB axons grew excessively, suggesting that these kinases inhibit regenerative sprouting in damaged axons. Uninjured trigeminal sensory axons also grew excessively in mutants when neighboring neurons were ablated, indicating that these MAP3Ks are general inhibitors of sensory axon growth. These results demonstrate that zebrafish DLK and LZK promote diverse injury responses, depending on the neuronal cell identity and type of axonal injury.SIGNIFICANCE STATEMENT The MAP3Ks DLK and LZK are damage sensors that promote diverse outcomes to neuronal injury, including axon regeneration. Understanding their context-specific functions is a prerequisite to considering these kinases as therapeutic targets. To investigate DLK and LZK cell-type-specific functions, we created zebrafish mutants in each gene. Using mosaic cell labeling and precise laser injury we found that both proteins were required for axon regeneration in motor neurons but, unexpectedly, were not required for axon regeneration in Rohon-Beard or DRG sensory neurons and negatively regulated sprouting in the spared axons of touch-sensing neurons. These findings emphasize that animals have evolved distinct mechanisms to regulate injury site regeneration and collateral sprouting, and identify differential roles for DLK and LZK in these processes.
Collapse
Affiliation(s)
- Kadidia Pemba Adula
- Molecular, Cell and Developmental Biology Department and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California 90095
| | - Matthew Shorey
- Department of Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania 16802
| | - Vasudha Chauhan
- Molecular, Cell and Developmental Biology Department and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California 90095
| | - Khaled Nassman
- Molecular, Cell and Developmental Biology Department and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California 90095
| | - Shu-Fan Chen
- Molecular, Cell and Developmental Biology Department and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California 90095
| | - Melissa M Rolls
- Department of Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania 16802
| | - Alvaro Sagasti
- Molecular, Cell and Developmental Biology Department and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California 90095,
| |
Collapse
|
5
|
Lu TQ, van Loon AP, Sagasti A. How to wrinkle a cell: Emerging mechanisms of microridge morphogenesis. Curr Opin Cell Biol 2022; 76:102088. [DOI: 10.1016/j.ceb.2022.102088] [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] [Received: 02/04/2022] [Revised: 03/27/2022] [Accepted: 04/05/2022] [Indexed: 11/26/2022]
|
6
|
van Loon AP, Erofeev IS, Goryachev AB, Sagasti A. Stochastic contraction of myosin minifilaments drives evolution of microridge protrusion patterns in epithelial cells. Mol Biol Cell 2021; 32:1501-1513. [PMID: 34081537 PMCID: PMC8351741 DOI: 10.1091/mbc.e21-05-0258] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [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: 05/20/2021] [Accepted: 05/26/2021] [Indexed: 01/05/2023] Open
Abstract
Actin-based protrusions vary in morphology, stability, and arrangement on cell surfaces. Microridges are laterally elongated protrusions on mucosal epithelial cells, where they form evenly spaced, mazelike patterns that dynamically remodel by fission and fusion. To characterize how microridges form their highly ordered, subcellular patterns and investigate the mechanisms driving fission and fusion, we imaged microridges in the maturing skin of zebrafish larvae. After their initial development, microridge spacing and alignment became increasingly well ordered. Imaging F-actin and non-muscle myosin II (NMII) revealed that microridge fission and fusion were associated with local NMII activity in the apical cortex. Inhibiting NMII blocked fission and fusion rearrangements, reduced microridge density, and altered microridge spacing. High-resolution imaging allowed us to image individual NMII minifilaments in the apical cortex of cells in live animals, revealing that minifilaments are tethered to protrusions and often connect adjacent microridges. NMII minifilaments connecting the ends of two microridges fused them together, whereas minifilaments oriented perpendicular to microridges severed them or pulled them closer together. These findings demonstrate that as cells mature, cortical NMII activity orchestrates a remodeling process that creates an increasingly orderly microridge arrangement.
Collapse
Affiliation(s)
- Aaron P. van Loon
- Department of Molecular, Cell and Developmental Biology, and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA
| | - Ivan S. Erofeev
- Centre for Synthetic and Systems Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Andrew B. Goryachev
- Centre for Synthetic and Systems Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Alvaro Sagasti
- Department of Molecular, Cell and Developmental Biology, and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA
| |
Collapse
|
7
|
Shorey M, Rao K, Stone MC, Mattie FJ, Sagasti A, Rolls MM. Microtubule organization of vertebrate sensory neurons in vivo. Dev Biol 2021; 478:1-12. [PMID: 34147472 DOI: 10.1016/j.ydbio.2021.06.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [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: 05/18/2021] [Revised: 06/11/2021] [Accepted: 06/12/2021] [Indexed: 01/30/2023]
Abstract
Dorsal root ganglion (DRG) neurons are the predominant cell type that innervates the vertebrate skin. They are typically described as pseudounipolar cells that have central and peripheral axons branching from a single root exiting the cell body. The peripheral axon travels within a nerve to the skin, where free sensory endings can emerge and branch into an arbor that receives and integrates information. In some immature vertebrates, DRG neurons are preceded by Rohon-Beard (RB) neurons. While the sensory endings of RB and DRG neurons function like dendrites, we use live imaging in zebrafish to show that they have axonal plus-end-out microtubule polarity at all stages of maturity. Moreover, we show both cell types have central and peripheral axons with plus-end-out polarity. Surprisingly, in DRG neurons these emerge separately from the cell body, and most cells never acquire the signature pseudounipolar morphology. Like another recently characterized cell type that has multiple plus-end-out neurites, ganglion cells in Nematostella, RB and DRG neurons maintain a somatic microtubule organizing center even when mature. In summary, we characterize key cellular and subcellular features of vertebrate sensory neurons as a foundation for understanding their function and maintenance.
Collapse
Affiliation(s)
- Matthew Shorey
- Department of Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Kavitha Rao
- Department of Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Michelle C Stone
- Department of Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Floyd J Mattie
- Department of Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Alvaro Sagasti
- Molecular, Cell and Developmental Biology Department and Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA
| | - Melissa M Rolls
- Department of Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA, 16802, USA.
| |
Collapse
|
8
|
van Loon AP, Erofeev IS, Maryshev IV, Goryachev AB, Sagasti A. Cortical contraction drives the 3D patterning of epithelial cell surfaces. J Cell Biol 2020; 219:133677. [PMID: 32003768 PMCID: PMC7054995 DOI: 10.1083/jcb.201904144] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [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: 04/23/2019] [Revised: 09/16/2019] [Accepted: 12/17/2019] [Indexed: 12/20/2022] Open
Abstract
Cellular protrusions create complex cell surface topographies, but biomechanical mechanisms regulating their formation and arrangement are largely unknown. To study how protrusions form, we focused on the morphogenesis of microridges, elongated actin-based structures that are arranged in maze-like patterns on the apical surfaces of zebrafish skin cells. Microridges form by accreting simple finger-like precursors. Live imaging demonstrated that microridge morphogenesis is linked to apical constriction. A nonmuscle myosin II (NMII) reporter revealed pulsatile contractions of the actomyosin cortex, and inhibiting NMII blocked apical constriction and microridge formation. A biomechanical model suggested that contraction reduces surface tension to permit the fusion of precursors into microridges. Indeed, reducing surface tension with hyperosmolar media promoted microridge formation. In anisotropically stretched cells, microridges formed by precursor fusion along the stretch axis, which computational modeling explained as a consequence of stretch-induced cortical flow. Collectively, our results demonstrate how contraction within the 2D plane of the cortex can pattern 3D cell surfaces.
Collapse
Affiliation(s)
- Aaron P van Loon
- Department of Molecular, Cell and Developmental Biology and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA
| | - Ivan S Erofeev
- Centre for Synthetic and Systems Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Ivan V Maryshev
- Centre for Synthetic and Systems Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Andrew B Goryachev
- Centre for Synthetic and Systems Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Alvaro Sagasti
- Department of Molecular, Cell and Developmental Biology and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA
| |
Collapse
|
9
|
Inaba Y, Chauhan V, van Loon AP, Choudhury LS, Sagasti A. Keratins and the plakin family cytolinker proteins control the length of epithelial microridge protrusions. eLife 2020; 9:58149. [PMID: 32894222 PMCID: PMC7535935 DOI: 10.7554/elife.58149] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [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] [Received: 04/22/2020] [Accepted: 09/04/2020] [Indexed: 02/06/2023] Open
Abstract
Actin filaments and microtubules create diverse cellular protrusions, but intermediate filaments, the strongest and most stable cytoskeletal elements, are not known to directly participate in the formation of protrusions. Here we show that keratin intermediate filaments directly regulate the morphogenesis of microridges, elongated protrusions arranged in elaborate maze-like patterns on the surface of mucosal epithelial cells. We found that microridges on zebrafish skin cells contained both actin and keratin filaments. Keratin filaments stabilized microridges, and overexpressing keratins lengthened them. Envoplakin and periplakin, plakin family cytolinkers that bind F-actin and keratins, localized to microridges, and were required for their morphogenesis. Strikingly, plakin protein levels directly dictate microridge length. An actin-binding domain of periplakin was required to initiate microridge morphogenesis, whereas periplakin-keratin binding was required to elongate microridges. These findings separate microridge morphogenesis into distinct steps, expand our understanding of intermediate filament functions, and identify microridges as protrusions that integrate actin and intermediate filaments.
Collapse
Affiliation(s)
- Yasuko Inaba
- Molecular, Cell and Developmental Biology Department and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, United States
| | - Vasudha Chauhan
- Molecular, Cell and Developmental Biology Department and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, United States
| | - Aaron Paul van Loon
- Molecular, Cell and Developmental Biology Department and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, United States
| | - Lamia Saiyara Choudhury
- Molecular, Cell and Developmental Biology Department and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, United States
| | - Alvaro Sagasti
- Molecular, Cell and Developmental Biology Department and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, United States
| |
Collapse
|
10
|
Feng C, Thyagarajan P, Shorey M, Seebold DY, Weiner AT, Albertson RM, Rao KS, Sagasti A, Goetschius DJ, Rolls MM. Patronin-mediated minus end growth is required for dendritic microtubule polarity. J Cell Biol 2019; 218:2309-2328. [PMID: 31076454 PMCID: PMC6605808 DOI: 10.1083/jcb.201810155] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [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: 10/26/2018] [Revised: 03/13/2019] [Accepted: 04/23/2019] [Indexed: 02/06/2023] Open
Abstract
Feng et al. describe persistent neuronal microtubule minus end growth that depends on the CAMSAP protein Patronin and is needed for dendritic minus-end-out polarity. Microtubule minus ends are thought to be stable in cells. Surprisingly, in Drosophila and zebrafish neurons, we observed persistent minus end growth, with runs lasting over 10 min. In Drosophila, extended minus end growth depended on Patronin, and Patronin reduction disrupted dendritic minus-end-out polarity. In fly dendrites, microtubule nucleation sites localize at dendrite branch points. Therefore, we hypothesized minus end growth might be particularly important beyond branch points. Distal dendrites have mixed polarity, and reduction of Patronin lowered the number of minus-end-out microtubules. More strikingly, extra Patronin made terminal dendrites almost completely minus-end-out, indicating low Patronin normally limits minus-end-out microtubules. To determine whether minus end growth populated new dendrites with microtubules, we analyzed dendrite development and regeneration. Minus ends extended into growing dendrites in the presence of Patronin. In sum, our data suggest that Patronin facilitates sustained microtubule minus end growth, which is critical for populating dendrites with minus-end-out microtubules.
Collapse
Affiliation(s)
- Chengye Feng
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA
| | - Pankajam Thyagarajan
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA
| | - Matthew Shorey
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA
| | - Dylan Y Seebold
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA
| | - Alexis T Weiner
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA
| | - Richard M Albertson
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA
| | - Kavitha S Rao
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA
| | - Alvaro Sagasti
- Molecular, Cell, and Developmental Biology, University of California, Los Angeles, Los Angeles, CA
| | - Daniel J Goetschius
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA
| | - Melissa M Rolls
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA
| |
Collapse
|
11
|
Rosa JB, Sagasti A. Developmental Neurobiology: It Takes Nrg to Separate Dendrites. Curr Biol 2019; 29:R327-R329. [PMID: 31063725 DOI: 10.1016/j.cub.2019.03.045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The development of sensory receptive fields requires the coordinated spatial patterning of neurites from multiple sensory neuron subtypes. A new study identifies a role for neuron-skin cell interactions in preventing the bundling of dendritic arbors from distinct neurons.
Collapse
Affiliation(s)
- Jeffrey B Rosa
- Department of Molecular, Cell, and Developmental Biology, UCLA, Los Angeles, CA 90095-1606, USA
| | - Alvaro Sagasti
- Department of Molecular, Cell, and Developmental Biology, UCLA, Los Angeles, CA 90095-1606, USA.
| |
Collapse
|
12
|
Jiang N, Rasmussen JP, Clanton JA, Rosenberg MF, Luedke KP, Cronan MR, Parker ED, Kim HJ, Vaughan JC, Sagasti A, Parrish JZ. A conserved morphogenetic mechanism for epidermal ensheathment of nociceptive sensory neurites. eLife 2019; 8:42455. [PMID: 30855229 PMCID: PMC6450671 DOI: 10.7554/elife.42455] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [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] [Received: 09/30/2018] [Accepted: 03/08/2019] [Indexed: 12/13/2022] Open
Abstract
Interactions between epithelial cells and neurons influence a range of sensory modalities including taste, touch, and smell. Vertebrate and invertebrate epidermal cells ensheath peripheral arbors of somatosensory neurons, including nociceptors, yet the developmental origins and functional roles of this ensheathment are largely unknown. Here, we describe an evolutionarily conserved morphogenetic mechanism for epidermal ensheathment of somatosensory neurites. We found that somatosensory neurons in Drosophila and zebrafish induce formation of epidermal sheaths, which wrap neurites of different types of neurons to different extents. Neurites induce formation of plasma membrane phosphatidylinositol 4,5-bisphosphate microdomains at nascent sheaths, followed by a filamentous actin network, and recruitment of junctional proteins that likely form autotypic junctions to seal sheaths. Finally, blocking epidermal sheath formation destabilized dendrite branches and reduced nociceptive sensitivity in Drosophila. Epidermal somatosensory neurite ensheathment is thus a deeply conserved cellular process that contributes to the morphogenesis and function of nociceptive sensory neurons. Humans and other animals perceive and interact with the outside world through their sensory nervous system. Nerve cells, acting as the body’s ‘telegraph wires’, convey signals from sensory organs – like the eyes – to the brain, which then processes this information and tells the body how to respond. There are different kinds of sensory nerve cells that carry different types of information, but they all associate closely with the tissues and organs they connect to the brain. Human skin contains sensory nerve cells, which underpin our senses of touch and pain. There is a highly specialized, complex connection between some of these nerve cells and cells in the skin: the skin cells wrap tightly around the nerve cells’ free ends, forming sheath-like structures. This ‘ensheathment’ process happens in a wide range of animals, including those with a backbone, like fish and humans, and those without, like insects. Ensheathment is thought to be important for the skin’s nerve cells to work properly. Yet it remains unclear how or when these connections first appear. Jiang et al. therefore wanted to determine the developmental origins of ensheathment and to find out if these were also similar in animals with and without backbones. Experiments using fruit fly and zebrafish embryos revealed that nerve cells, not skin cells, were responsible for forming and maintaining the sheaths. In embryos where groups of sensory nerve cells were selectively killed – either using a laser or by making the cells produce a toxin – ensheathment did not occur. Further studies, using a variety of microscopy techniques, revealed that the molecular machinery required to stabilize the sheaths was similar in both fish and flies, and therefore likely to be conserved across different groups of animals. Removing sheaths in fly embryos led to nerve cells becoming unstable; the animals were also less sensitive to touch. This confirmed that ensheathment was indeed necessary for sensory nerve cells to work properly. By revealing how ensheathment first emerges, these findings shed new light on how the sensory nervous system develops and how its activity is controlled. In humans, skin cells ensheath the nerve cells responsible for sensing pain. A better understanding of how ensheathments first arise could therefore lead to new avenues for treating chronic pain and related conditions.
Collapse
Affiliation(s)
- Nan Jiang
- Department of Biology, University of Washington, Seattle, United States
| | - Jeffrey P Rasmussen
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, United States
| | - Joshua A Clanton
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, United States
| | - Marci F Rosenberg
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, United States
| | - Kory P Luedke
- Department of Biology, University of Washington, Seattle, United States
| | - Mark R Cronan
- Department of Molecular Genetics and Microbiology, Duke University, Durham, United States
| | - Edward D Parker
- Department of Opthalmology, University of Washington, Seattle, United States
| | - Hyeon-Jin Kim
- Department of Chemistry, University of Washington, Seattle, United States.,Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Joshua C Vaughan
- Department of Chemistry, University of Washington, Seattle, United States.,Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Alvaro Sagasti
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, United States
| | - Jay Z Parrish
- Department of Biology, University of Washington, Seattle, United States
| |
Collapse
|
13
|
Julien DP, Chan AW, Barrios J, Mathiaparanam J, Douglass A, Wolman MA, Sagasti A. Zebrafish expression reporters and mutants reveal that the IgSF cell adhesion molecule Dscamb is required for feeding and survival. J Neurogenet 2018; 32:336-352. [PMID: 30204029 DOI: 10.1080/01677063.2018.1493479] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Down syndrome cell adhesion molecules (DSCAMs) are broadly expressed in nervous systems and play conserved roles in programmed cell death, neuronal migration, axon guidance, neurite branching and spacing, and synaptic targeting. However, DSCAMs appear to have distinct functions in different vertebrate animals, and little is known about their functions outside the retina. We leveraged the genetic tractability and optical accessibility of larval zebrafish to investigate the expression and function of a DSCAM family member, dscamb. Using targeted genome editing to create transgenic reporters and loss-of-function mutant alleles, we discovered that dscamb is expressed broadly throughout the brain, spinal cord, and peripheral nervous system, but is not required for overall structural organization of the brain. Despite the absence of obvious anatomical defects, homozygous dscamb mutants were deficient in their ability to ingest food and rarely survived to adulthood. Thus, we have discovered a novel function for dscamb in feeding behavior. The mutant and transgenic lines generated in these studies will provide valuable tools for identifying the molecular and cellular bases of these behaviors.
Collapse
Affiliation(s)
- Donald P Julien
- a Department of Molecular, Cell and Developmental Biology and Molecular Biology Institute , University of California , Los Angeles , CA , USA
| | - Alex W Chan
- a Department of Molecular, Cell and Developmental Biology and Molecular Biology Institute , University of California , Los Angeles , CA , USA
| | - Joshua Barrios
- b Department of Neurobiology and Anatomy , University of Utah , Salt Lake City , UT , USA
| | - Jaffna Mathiaparanam
- c Department of Integrative Biology , University of Wisconsin , Madison , WI , USA
| | - Adam Douglass
- b Department of Neurobiology and Anatomy , University of Utah , Salt Lake City , UT , USA
| | - Marc A Wolman
- c Department of Integrative Biology , University of Wisconsin , Madison , WI , USA
| | - Alvaro Sagasti
- a Department of Molecular, Cell and Developmental Biology and Molecular Biology Institute , University of California , Los Angeles , CA , USA
| |
Collapse
|
14
|
Madigan CA, Cambier CJ, Kelly-Scumpia KM, Scumpia PO, Cheng TY, Zailaa J, Bloom BR, Moody DB, Smale ST, Sagasti A, Modlin RL, Ramakrishnan L. A Macrophage Response to Mycobacterium leprae Phenolic Glycolipid Initiates Nerve Damage in Leprosy. Cell 2017; 170:973-985.e10. [PMID: 28841420 PMCID: PMC5848073 DOI: 10.1016/j.cell.2017.07.030] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [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: 03/26/2017] [Revised: 05/13/2017] [Accepted: 07/19/2017] [Indexed: 12/21/2022]
Abstract
Mycobacterium leprae causes leprosy and is unique among mycobacterial diseases in producing peripheral neuropathy. This debilitating morbidity is attributed to axon demyelination resulting from direct interaction of the M. leprae-specific phenolic glycolipid 1 (PGL-1) with myelinating glia and their subsequent infection. Here, we use transparent zebrafish larvae to visualize the earliest events of M. leprae-induced nerve damage. We find that demyelination and axonal damage are not directly initiated by M. leprae but by infected macrophages that patrol axons; demyelination occurs in areas of intimate contact. PGL-1 confers this neurotoxic response on macrophages: macrophages infected with M. marinum-expressing PGL-1 also damage axons. PGL-1 induces nitric oxide synthase in infected macrophages, and the resultant increase in reactive nitrogen species damages axons by injuring their mitochondria and inducing demyelination. Our findings implicate the response of innate macrophages to M. leprae PGL-1 in initiating nerve damage in leprosy.
Collapse
Affiliation(s)
- Cressida A Madigan
- Division of Dermatology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Microbiology, University of Washington, Seattle, WA 98195, USA.
| | - C J Cambier
- Department of Immunology, University of Washington, Seattle, WA 98195, USA
| | - Kindra M Kelly-Scumpia
- Division of Dermatology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Philip O Scumpia
- Division of Dermatology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Tan-Yun Cheng
- Division of Rheumatology, Immunology, and Allergy, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Joseph Zailaa
- Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Barry R Bloom
- Harvard School of Public Health, Boston, MA 02115, USA
| | - D Branch Moody
- Division of Rheumatology, Immunology, and Allergy, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Stephen T Smale
- Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Alvaro Sagasti
- Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Robert L Modlin
- Division of Dermatology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Lalita Ramakrishnan
- Department of Microbiology, University of Washington, Seattle, WA 98195, USA; Department of Immunology, University of Washington, Seattle, WA 98195, USA; Department of Medicine, University of Washington, Seattle, WA 98195, USA; MRC Laboratory of Molecular Biology, Molecular Immunity Unit, Department of Medicine, University of Cambridge, Cambridge CB2 OQH, UK.
| |
Collapse
|
15
|
Lulla A, Barnhill L, Bitan G, Ivanova MI, Nguyen B, O’Donnell K, Stahl MC, Yamashiro C, Klärner FG, Schrader T, Sagasti A, Bronstein JM. Neurotoxicity of the Parkinson Disease-Associated Pesticide Ziram Is Synuclein-Dependent in Zebrafish Embryos. Environ Health Perspect 2016; 124:1766-1775. [PMID: 27301718 PMCID: PMC5089875 DOI: 10.1289/ehp141] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2015] [Revised: 02/21/2016] [Accepted: 05/12/2016] [Indexed: 05/29/2023]
Abstract
BACKGROUND Exposure to the commonly used dithiocarbamate (DTC) pesticides is associated with an increased risk of developing Parkinson disease (PD), although the mechanisms by which they exert their toxicity are not completely understood. OBJECTIVE We studied the mechanisms of ziram's (a DTC fungicide) neurotoxicity in vivo. METHODS Zebrafish (ZF) embryos were utilized to determine ziram's effects on behavior, neuronal toxicity, and the role of synuclein in its toxicity. RESULTS Nanomolar-range concentrations of ziram caused selective loss of dopaminergic (DA) neurons and impaired swimming behavior. Because ziram increases α-synuclein (α-syn) concentrations in rat primary neuronal cultures, we investigated the effect of ziram on ZF γ-synuclein 1 (γ1). ZF express 3 synuclein isoforms, and ZF γ1 appears to be the closest functional homologue to α-syn. We found that recombinant ZF γ1 formed fibrils in vitro, and overexpression of ZF γ1 in ZF embryos led to the formation of neuronal aggregates and neurotoxicity in a manner similar to that of α-syn. Importantly, knockdown of ZF γ1 with morpholinos and disruption of oligomers with the molecular tweezer CLR01 prevented ziram's DA toxicity. CONCLUSIONS These data show that ziram is selectively toxic to DA neurons in vivo, and this toxicity is synuclein-dependent. These findings have important implications for understanding the mechanisms by which pesticides may cause PD. Citation: Lulla A, Barnhill L, Bitan G, Ivanova MI, Nguyen B, O'Donnell K, Stahl MC, Yamashiro C, Klärner FG, Schrader T, Sagasti A, Bronstein JM. 2016. Neurotoxicity of the Parkinson disease-associated pesticide ziram is synuclein-dependent in zebrafish embryos. Environ Health Perspect 124:1766-1775; http://dx.doi.org/10.1289/EHP141.
Collapse
Affiliation(s)
- Aaron Lulla
- Department of Neurology, University of Los Angeles (UCLA), Los Angeles, California, USA
| | - Lisa Barnhill
- Department of Neurology, University of Los Angeles (UCLA), Los Angeles, California, USA
| | - Gal Bitan
- Department of Neurology, University of Los Angeles (UCLA), Los Angeles, California, USA
- Brain Research Institute, and
- Molecular Biology Institute, UCLA, Los Angeles, California, USA
| | - Magdalena I. Ivanova
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California, USA
- UCLA-DOE Institute, UCLA, Los Angeles, California, USA
| | - Binh Nguyen
- Department of Neurology, University of Los Angeles (UCLA), Los Angeles, California, USA
| | - Kelley O’Donnell
- Department of Molecular, Cell, and Developmental Biology, UCLA, Los Angeles, California, USA
| | - Mark C. Stahl
- Department of Neurology, University of Los Angeles (UCLA), Los Angeles, California, USA
| | - Chase Yamashiro
- Department of Neurology, University of Los Angeles (UCLA), Los Angeles, California, USA
| | | | - Thomas Schrader
- Institute of Organic Chemistry, University of Duisburg-Essen, Essen, Germany
| | - Alvaro Sagasti
- Department of Molecular, Cell, and Developmental Biology, UCLA, Los Angeles, California, USA
| | - Jeff M. Bronstein
- Department of Neurology, University of Los Angeles (UCLA), Los Angeles, California, USA
- Brain Research Institute, and
- Parkinson’s Disease Research, Education, and Clinical Center, Greater Los Angeles Veterans Affairs Medical Center, Los Angeles, California, USA
| |
Collapse
|
16
|
Julien DP, Sagasti A. Synaptic specificity: when the neighbors are away, sensory axons turn promiscuous. Curr Biol 2014; 24:R1168-70. [PMID: 25514010 DOI: 10.1016/j.cub.2014.11.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A new study describes cellular mechanisms establishing synaptic specificity during development and remodeling of a zebrafish mechanosensory organ. Coordination amongst postsynaptic neurons and interactions between presynaptic and postsynaptic cells together promote the segregation of circuits responding to distinct sensory stimuli.
Collapse
Affiliation(s)
- Donald P Julien
- Department of Molecular, Cell, and Developmental Biology, UCLA, Los Angeles, CA 90095-1606, USA
| | - Alvaro Sagasti
- Department of Molecular, Cell, and Developmental Biology, UCLA, Los Angeles, CA 90095-1606, USA.
| |
Collapse
|
17
|
Chun RF, Blatter E, Elliott S, Fitz-Gibbon S, Rieger S, Sagasti A, Adams JS, Hewison M. Cloning of a functional 25-hydroxyvitamin D-1α-hydroxylase in zebrafish (Danio rerio). Cell Biochem Funct 2014; 32:675-82. [PMID: 25290078 DOI: 10.1002/cbf.3071] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [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: 04/29/2014] [Revised: 09/17/2014] [Accepted: 09/18/2014] [Indexed: 12/14/2022]
Abstract
Activation of precursor 25-hydroxyvitamin D3 (25D) to hormonal 1,25-dihydroxyvitamin D3 (1,25D) is a pivotal step in vitamin D physiology, catalysed by the enzyme 25-hydroxyvitamin D-1α-hydroxylase (1α-hydroxylase). To establish new models for assessing the physiological importance of the 1α-hydroxylase-25D-axis, we used Danio rerio (zebrafish) to characterize expression and biological activity of the gene for 1α-hydroxylase (cyp27b1). Treatment of day 5 zebrafish larvae with inactive 25D (5-150 nM) or active 1,25D (0.1-10 nM) induced dose responsive expression (15-95-fold) of the vitamin D-target gene cyp24a1 relative to larvae treated with vehicle, suggesting the presence of Cyp27b1 activity. A full-length zebrafish cyp27b1 cDNA was then generated using RACE and RT-PCR methods. Sequencing of the resulting clone revealed an open reading frame encoding a protein of 505 amino acids with 54% identity to human CYP27B1. Transfection of a cyp27b1 expression vector into HKC-8, a human kidney proximal tubular epithelial cell line, enhanced intracrine metabolism of 25D to 1,25D resulting in greater than twofold induction of CYP24A1 mRNA expression and a 25-fold increase in 1,25D production compared to empty vector. These data indicate that we have cloned a functional zebrafish CYP27B1, representing a phylogenetically distant branch from mammals of this key enzyme in vitamin D metabolism. Further analysis of cyp27b1 expression and activity in zebrafish may provide new perspectives on the biological importance of 25D metabolism.
Collapse
Affiliation(s)
- Rene F Chun
- Department of Orthopaedic Surgery, UCLA-Orthopaedic Hospital, Los Angeles, CA, 90095, United States
| | | | | | | | | | | | | | | |
Collapse
|
18
|
O'Donnell KC, Lulla A, Stahl MC, Wheat ND, Bronstein JM, Sagasti A. Axon degeneration and PGC-1α-mediated protection in a zebrafish model of α-synuclein toxicity. Dis Model Mech 2014; 7:571-82. [PMID: 24626988 PMCID: PMC4007408 DOI: 10.1242/dmm.013185] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
α-synuclein (aSyn) expression is implicated in neurodegenerative processes, including Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). In animal models of these diseases, axon pathology often precedes cell death, raising the question of whether aSyn has compartment-specific toxic effects that could require early and/or independent therapeutic intervention. The relevance of axonal pathology to degeneration can only be addressed through longitudinal, in vivo monitoring of different neuronal compartments. With current imaging methods, dopaminergic neurons do not readily lend themselves to such a task in any vertebrate system. We therefore expressed human wild-type aSyn in zebrafish peripheral sensory neurons, which project elaborate superficial axons that can be continuously imaged in vivo. Axonal outgrowth was normal in these neurons but, by 2 days post-fertilization (dpf), many aSyn-expressing axons became dystrophic, with focal varicosities or diffuse beading. Approximately 20% of aSyn-expressing cells died by 3 dpf. Time-lapse imaging revealed that focal axonal swelling, but not overt fragmentation, usually preceded cell death. Co-expressing aSyn with a mitochondrial reporter revealed deficits in mitochondrial transport and morphology even when axons appeared overtly normal. The axon-protective protein Wallerian degeneration slow (WldS) delayed axon degeneration but not cell death caused by aSyn. By contrast, the transcriptional coactivator PGC-1α, which has roles in the regulation of mitochondrial biogenesis and reactive-oxygen-species detoxification, abrogated aSyn toxicity in both the axon and the cell body. The rapid onset of axonal pathology in this system, and the relatively moderate degree of cell death, provide a new model for the study of aSyn toxicity and protection. Moreover, the accessibility of peripheral sensory axons will allow effects of aSyn to be studied in different neuronal compartments and might have utility in screening for novel disease-modifying compounds.
Collapse
Affiliation(s)
- Kelley C O'Donnell
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, CA 90095, USA
| | | | | | | | | | | |
Collapse
|
19
|
Abstract
The peripheral axons of vertebrate tactile somatosensory neurons travel long distances from ganglia just outside the central nervous system to the skin. Once in the skin these axons form elaborate terminals whose organization must be regionally patterned to detect and accurately localize different kinds of touch stimuli. This review describes key studies that identified choice points for somatosensory axon growth cones and the extrinsic molecular cues that function at each of those steps. While much has been learned in the past 20 years about the guidance of these axons, there is still much to be learned about how the peripheral axons of different kinds of somatosensory neurons adopt different trajectories and form specific terminal structures.
Collapse
Affiliation(s)
- Fang Wang
- Department of Molecular, Cell and Developmental Biology; University of California, Los Angeles; Los Angeles, CA USA
| | | | | |
Collapse
|
20
|
Abstract
Larval zebrafish are emerging as a model for describing the development and function of simple neural circuits. Due to their external fertilization, rapid development, and translucency, zebrafish are particularly well suited for optogenetic approaches to investigate neural circuit function. In this approach, light-sensitive ion channels are expressed in specific neurons, enabling the experimenter to activate or inhibit them at will and thus assess their contribution to specific behaviors. Applying these methods in larval zebrafish is conceptually simple but requires the optimization of technical details. Here we demonstrate a procedure for expressing a channelrhodopsin variant in larval zebrafish somatosensory neurons, photo-activating single cells, and recording the resulting behaviors. By introducing a few modifications to previously established methods, this approach could be used to elicit behavioral responses from single neurons activated up to at least 4 days post-fertilization (dpf). Specifically, we created a transgene using a somatosensory neuron enhancer, CREST3, to drive the expression of the tagged channelrhodopsin variant, ChEF-tdTomato. Injecting this transgene into 1-cell stage embryos results in mosaic expression in somatosensory neurons, which can be imaged with confocal microscopy. Illuminating identified cells in these animals with light from a 473 nm DPSS laser, guided through a fiber optic cable, elicits behaviors that can be recorded with a high-speed video camera and analyzed quantitatively. This technique could be adapted to study behaviors elicited by activating any zebrafish neuron. Combining this approach with genetic or pharmacological perturbations will be a powerful way to investigate circuit formation and function.
Collapse
Affiliation(s)
- Ana Marie S Palanca
- Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, USA
| | | |
Collapse
|
21
|
Palanca AMS, Lee SL, Yee LE, Joe-Wong C, Trinh LA, Hiroyasu E, Husain M, Fraser SE, Pellegrini M, Sagasti A. New transgenic reporters identify somatosensory neuron subtypes in larval zebrafish. Dev Neurobiol 2012; 73:152-67. [PMID: 22865660 DOI: 10.1002/dneu.22049] [Citation(s) in RCA: 46] [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: 07/02/2012] [Accepted: 07/26/2012] [Indexed: 12/22/2022]
Abstract
To analyze somatosensory neuron diversity in larval zebrafish, we identified several enhancers from the zebrafish and pufferfish genomes and used them to create five new reporter transgenes. Sequential deletions of three of these enhancers identified small sequence elements sufficient to drive expression in zebrafish trigeminal and Rohon-Beard (RB) neurons. One of these reporters, using the Fru.p2x3-2 enhancer, highlighted a somatosensory neuron subtype that expressed both the p2rx3a and pkcα genes. Comparison with a previously described trpA1b reporter revealed that it highlighted the same neurons as the Fru.p2x3-2 reporter. To determine whether neurons of this subtype possess characteristic peripheral branching morphologies or central axon projection patterns, we analyzed the morphology of single neurons. Surprisingly, although these analyses revealed diversity in peripheral axon branching and central axon projection, PKCα/p2rx3a/trpA1b-expressing RB cells did not possess obvious characteristic morphological features, suggesting that even within this molecularly defined subtype, individual neurons may possess distinct properties. The new transgenes created in this study will be powerful tools for further characterizing the molecular, morphological, and developmental diversity of larval somatosensory neurons.
Collapse
Affiliation(s)
- Ana Marie S Palanca
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles 90095, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Issa FA, Mock AF, Sagasti A, Papazian DM. Spinocerebellar ataxia type 13 mutation that is associated with disease onset in infancy disrupts axonal pathfinding during neuronal development. Dis Model Mech 2012; 5:921-9. [PMID: 22736459 PMCID: PMC3484873 DOI: 10.1242/dmm.010157] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Spinocerebellar ataxia type 13 (SCA13) is an autosomal dominant disease caused by mutations in the Kv3.3 voltage-gated potassium (K+) channel. SCA13 exists in two forms: infant onset is characterized by severe cerebellar atrophy, persistent motor deficits and intellectual disability, whereas adult onset is characterized by progressive ataxia and progressive cerebellar degeneration. To test the hypothesis that infant- and adult-onset mutations have differential effects on neuronal development that contribute to the age at which SCA13 emerges, we expressed wild-type Kv3.3 or infant- or adult-onset mutant proteins in motor neurons in the zebrafish spinal cord. We characterized the development of CaP (caudal primary) motor neurons at ∼36 and ∼48 hours post-fertilization using confocal microscopy and 3D digital reconstruction. Exogenous expression of wild-type Kv3.3 had no significant effect on CaP development. In contrast, CaP neurons expressing the infant-onset mutation made frequent pathfinding errors, sending long, abnormal axon collaterals into muscle territories that are normally innervated exclusively by RoP (rostral primary) or MiP (middle primary) motor neurons. This phenotype might be directly relevant to infant-onset SCA13 because interaction with inappropriate synaptic partners might trigger cell death during brain development. Importantly, pathfinding errors were not detected in CaP neurons expressing the adult-onset mutation. However, the adult-onset mutation tended to increase the complexity of the distal axonal arbor. From these results, we speculate that infant-onset SCA13 is associated with marked changes in the development of Kv3.3-expressing cerebellar neurons, reducing their health and viability early in life and resulting in the withered cerebellum seen in affected children.
Collapse
Affiliation(s)
- Fadi A Issa
- Department of Physiology, University of California at Los Angeles, Los Angeles, CA 90095-1751, USA
| | | | | | | |
Collapse
|
23
|
Villegas R, Martin SM, O'Donnell KC, Carrillo SA, Sagasti A, Allende ML. Dynamics of degeneration and regeneration in developing zebrafish peripheral axons reveals a requirement for extrinsic cell types. Neural Dev 2012; 7:19. [PMID: 22681863 PMCID: PMC3780720 DOI: 10.1186/1749-8104-7-19] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [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: 11/28/2011] [Accepted: 05/01/2012] [Indexed: 11/29/2022] Open
Abstract
Background Understanding the cellular mechanisms regulating axon degeneration and
regeneration is crucial for developing treatments for nerve injury and
neurodegenerative disease. In neurons, axon degeneration is distinct from cell
body death and often precedes or is associated with the onset of disease symptoms.
In the peripheral nervous system of both vertebrates and invertebrates, after
degeneration of detached fragments, axons can often regenerate to restore
function. Many studies of axonal degeneration and regeneration have used in vitro
approaches, but the influence of extrinsic cell types on these processes can only
be fully addressed in live animals. Because of its simplicity and superficial
location, the larval zebrafish posterior lateral line (pLL) nerve is an ideal
model system for live studies of axon degeneration and regeneration. Results We used laser axotomy and time-lapse imaging of pLL axons to characterize the
roles of leukocytes, Schwann cells and target sensory hair cells in axon
degeneration and regeneration in vivo. Immune cells were essential for efficient
removal of axonal debris after axotomy. Schwann cells were required for proper
fasciculation and pathfinding of regenerating axons to their target cells. Intact
target hair cells were not themselves required for regeneration, but chemical
ablation of neuromasts caused axons to transiently deviate from their normal
paths. Conclusions Macrophages, Schwann cells, and target sensory organs are required for distinct
aspects of pLL axon degeneration or regeneration in the zebrafish larva. Our work
introduces a powerful vertebrate model for analyzing axonal degeneration and
regeneration in the living animal and elucidating the role of extrinsic cell types
in these processes.
Collapse
Affiliation(s)
- Rosario Villegas
- FONDAP Center for Genome Regulation, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Santiago, Chile
| | | | | | | | | | | |
Collapse
|
24
|
O'Brien GS, Rieger S, Wang F, Smolen GA, Gonzalez RE, Buchanan J, Sagasti A. Coordinate development of skin cells and cutaneous sensory axons in zebrafish. J Comp Neurol 2012; 520:816-31. [PMID: 22020759 DOI: 10.1002/cne.22791] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Peripheral sensory axons innervate the epidermis early in embryogenesis to detect touch stimuli. To characterize the time course of cutaneous innervation and the nature of interactions between sensory axons and skin cells at early developmental stages, we conducted a detailed analysis of cutaneous innervation in the head, trunk, and tail of zebrafish embryos and larvae from 18 to 78 hours postfertilization. This analysis combined live imaging of fish expressing transgenes that highlight sensory neurons and skin cells, transmission electron microscopy (TEM), and serial scanning electron microscopy (sSEM). In zebrafish, the skin initially consists of two epithelial layers, and all of the axons in the first wave of innervation are free endings. Maturation of the epithelium coincides with, but does not depend on, its innervation by peripheral sensory axons. We found that peripheral axons initially arborize between the two epithelial skin layers, but not within the basal lamina, as occurs in other organisms. Strikingly, as development proceeds, axons become tightly enveloped within basal keratinocytes, an arrangement suggesting that keratinocytes may serve structural or functional roles, akin to Schwann cells, in somatosensation mediated by these sensory neurons.
Collapse
Affiliation(s)
- Georgeann S O'Brien
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, California 90095, USA
| | | | | | | | | | | | | |
Collapse
|
25
|
Rieger S, Sagasti A. Hydrogen peroxide promotes injury-induced peripheral sensory axon regeneration in the zebrafish skin. PLoS Biol 2011; 9:e1000621. [PMID: 21629674 PMCID: PMC3101194 DOI: 10.1371/journal.pbio.1000621] [Citation(s) in RCA: 125] [Impact Index Per Article: 9.6] [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: 09/02/2010] [Accepted: 04/14/2011] [Indexed: 02/01/2023] Open
Abstract
Production of H2O2 by injured zebrafish skin cells promotes the regeneration of nearby somatosensory axon terminals, thus coordinating wound healing of the skin with sensory reinnervation. Functional recovery from cutaneous injury requires not only the healing and regeneration of skin cells but also reinnervation of the skin by somatosensory peripheral axon endings. To investigate how sensory axon regeneration and wound healing are coordinated, we amputated the caudal fins of zebrafish larvae and imaged somatosensory axon behavior. Fin amputation strongly promoted the regeneration of nearby sensory axons, an effect that could be mimicked by ablating a few keratinocytes anywhere in the body. Since injury produces the reactive oxygen species hydrogen peroxide (H2O2) near wounds, we tested whether H2O2 influences cutaneous axon regeneration. Exposure of zebrafish larvae to sublethal levels of exogenous H2O2 promoted growth of severed axons in the absence of keratinocyte injury, and inhibiting H2O2 production blocked the axon growth-promoting effects of fin amputation and keratinocyte ablation. Thus, H2O2 signaling helps coordinate wound healing with peripheral sensory axon reinnervation of the skin. Touch-sensing neurons project axonal processes that branch extensively within the outer layers of skin to detect touch stimuli. Recovering from skin injuries thus requires not only repair of damaged skin tissue but also regeneration of the sensory axons innervating it. To study whether skin wound healing is coordinated with sensory innervation, we compared the regeneration of severed sensory axons innervating larval zebrafish tail fins with and without concomitant injury to surrounding skin cells. Severed axons regenerated more robustly when nearby skin cells were also damaged, suggesting that wounded skin releases a short-range factor that promotes axon growth. The reactive oxygen species hydrogen peroxide (H2O2) is known to be produced by injured cells, making it a candidate for mediating this signal. We found that adding exogenous H2O2 improved the regeneration of severed axons. Conversely, blocking H2O2 production prevented the axon growth-promoting effect of skin injury. Thus, H2O2 promotes axon growth after skin damage, helping to ensure that healing skin is properly innervated.
Collapse
Affiliation(s)
- Sandra Rieger
- Department of Molecular, Cell and Developmental Biology, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail: (AS); (SR)
| | - Alvaro Sagasti
- Department of Molecular, Cell and Developmental Biology, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail: (AS); (SR)
| |
Collapse
|
26
|
Rieger S, Wang F, Sagasti A. Time-lapse imaging of neural development: zebrafish lead the way into the fourth dimension. Genesis 2011; 49:534-45. [PMID: 21305690 DOI: 10.1002/dvg.20729] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [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: 11/19/2010] [Revised: 01/24/2011] [Accepted: 01/25/2011] [Indexed: 01/01/2023]
Abstract
Time-lapse imaging is often the only way to appreciate fully the many dynamic cell movements critical to neural development. Zebrafish possess many advantages that make them the best vertebrate model organism for live imaging of dynamic development events. This review will discuss technical considerations of time-lapse imaging experiments in zebrafish, describe selected examples of imaging studies in zebrafish that revealed new features or principles of neural development, and consider the promise and challenges of future time-lapse studies of neural development in zebrafish embryos and adults.
Collapse
Affiliation(s)
- Sandra Rieger
- Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, California, USA
| | | | | |
Collapse
|
27
|
Abstract
Examining neuronal network activity in freely behaving animals is advantageous for probing the function of the vertebrate central nervous system. Here, we describe a simple, robust technique for monitoring the activity of neural circuits in unfettered, freely behaving zebrafish (Danio rerio). Zebrafish respond to unexpected tactile stimuli with short- or long-latency escape behaviors, which are mediated by distinct neural circuits. Using dipole electrodes immersed in the aquarium, we measured electric field potentials generated in muscle during short- and long-latency escapes. We found that activation of the underlying neural circuits produced unique field potential signatures that are easily recognized and can be repeatedly monitored. In conjunction with behavioral analysis, we used this technique to track changes in the pattern of circuit activation during the first week of development in animals whose trigeminal sensory neurons were unilaterally ablated. One day post-ablation, the frequency of short- and long-latency responses was significantly lower on the ablated side than on the intact side. Three days post-ablation, a significant fraction of escapes evoked by stimuli on the ablated side was improperly executed, with the animal turning towards rather than away from the stimulus. However, the overall response rate remained low. Seven days post-ablation, the frequency of escapes increased dramatically and the percentage of improperly executed escapes declined. Our results demonstrate that trigeminal ablation results in rapid reconfiguration of the escape circuitry, with reinnervation by new sensory neurons and adaptive changes in behavior. This technique is valuable for probing the activity, development, plasticity and regeneration of neural circuits under natural conditions.
Collapse
Affiliation(s)
- Fadi A. Issa
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1751, USA
| | - Georgeann O'Brien
- Department of Molecular, Cell, and Developmental Biology, UCLA, Los Angeles, CA 90095-1606, USA
| | - Petronella Kettunen
- Department of Integrative Biology and Physiology, UCLA, Los Angeles, CA 90095-1568, USA
| | - Alvaro Sagasti
- Department of Molecular, Cell, and Developmental Biology, UCLA, Los Angeles, CA 90095-1606, USA
| | - David L. Glanzman
- Department of Integrative Biology and Physiology, UCLA, Los Angeles, CA 90095-1568, USA
| | - Diane M. Papazian
- Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1751, USA
| |
Collapse
|
28
|
Martin SM, O'Brien GS, Portera-Cailliau C, Sagasti A. Wallerian degeneration of zebrafish trigeminal axons in the skin is required for regeneration and developmental pruning. Development 2010; 137:3985-94. [PMID: 21041367 DOI: 10.1242/dev.053611] [Citation(s) in RCA: 78] [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: 11/20/2022]
Abstract
Fragments of injured axons that detach from their cell body break down by the molecularly regulated process of Wallerian degeneration (WD). Although WD resembles local axon degeneration, a common mechanism for refining neuronal structure, several previously examined instances of developmental pruning were unaffected by WD pathways. We used laser axotomy and time-lapse confocal imaging to characterize and compare peripheral sensory axon WD and developmental pruning in live zebrafish larvae. Detached fragments of single injured axon arbors underwent three stereotyped phases of WD: a lag phase, a fragmentation phase and clearance. The lag phase was developmentally regulated, becoming shorter as embryos aged, while the length of the clearance phase increased with the amount of axon debris. Both cell-specific inhibition of ubiquitylation and overexpression of the Wallerian degeneration slow protein (Wld(S)) lengthened the lag phase dramatically, but neither affected fragmentation. Persistent Wld(S)-expressing axon fragments directly repelled regenerating axon branches of their parent arbor, similar to self-repulsion among sister branches of intact arbors. Expression of Wld(S) also disrupted naturally occurring local axon pruning and axon degeneration in spontaneously dying trigeminal neurons: although pieces of Wld(S)-expressing axons were pruned, and some Wld(S)-expressing cells still died during development, in both cases detached axon fragments failed to degenerate. We propose that spontaneously pruned fragments of peripheral sensory axons must be removed by a WD-like mechanism to permit efficient innervation of the epidermis.
Collapse
Affiliation(s)
- Seanna M Martin
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, CA 90095, USA
| | | | | | | |
Collapse
|
29
|
Villegas R, Sagasti A, Allende ML. Degeneration–regeneration dynamics in the zebrafish lateral line nerve. Dev Biol 2010. [DOI: 10.1016/j.ydbio.2010.05.453] [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: 11/17/2022]
|
30
|
Abstract
The spatial pattern of branches within axonal or dendritic arbors and the relative arrangement of neighboring arbors with respect to one another impact a neuron's potential connectivity. Although arbors can adopt diverse branching patterns to suit their functions, evenly spread branches that avoid clumping or overlap are a common feature of many axonal and dendritic arbors. The degree of overlap between neighboring arbors innervating a surface is also characteristic within particular neuron types. The arbors of some populations of neurons innervate a target with a comprehensive and nonoverlapping "tiled" arrangement, whereas those of others show substantial territory overlap. This review focuses on cellular and molecular studies that have provided insight into the regulation of spatial arrangements of neurite branches within and between arbors. These studies have revealed principles that govern arbor arrangements in dendrites and axons in both vertebrates and invertebrates. Diverse molecular mechanisms controlling the spatial patterning of sister branches and neighboring arbors have begun to be elucidated.
Collapse
Affiliation(s)
- Wesley B Grueber
- Department of Physiology and Cellular Biophysics, Department of Neuroscience, Columbia University Medical Center, New York, New York 10032, USA.
| | | |
Collapse
|
31
|
O’Brien GS, Martin SM, Söllner C, Wright GJ, Becker CG, Portera-Cailliau C, Sagasti A. Developmentally regulated impediments to skin reinnervation by injured peripheral sensory axon terminals. Curr Biol 2009; 19:2086-90. [PMID: 19962310 PMCID: PMC2805760 DOI: 10.1016/j.cub.2009.10.051] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [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: 09/17/2009] [Revised: 10/15/2009] [Accepted: 10/15/2009] [Indexed: 11/26/2022]
Abstract
The structural plasticity of neurites in the central nervous system (CNS) diminishes dramatically after initial development, but the peripheral nervous system (PNS) retains substantial plasticity into adulthood. Nevertheless, functional reinnervation by injured peripheral sensory neurons is often incomplete [1-6]. To investigate the developmental control of skin reinnervation, we imaged the regeneration of trigeminal sensory axon terminals in live zebrafish larvae following laser axotomy. When axons were injured during early stages of outgrowth, regenerating and uninjured axons grew into denervated skin and competed with one another for territory. At later stages, after the establishment of peripheral arbor territories, the ability of uninjured neighbors to sprout diminished severely, and although injured axons reinitiated growth, they were repelled by denervated skin. Regenerating axons were repelled specifically by their former territories, suggesting that local inhibitory factors persist in these regions. Antagonizing the function of several members of the Nogo receptor (NgR)/RhoA pathway improved the capacity of injured axons to grow into denervated skin. Thus, as in the CNS, impediments to reinnervation in the PNS arise after initial establishment of axon arbor structure.
Collapse
Affiliation(s)
- Georgeann S. O’Brien
- Department of Molecular Cell and Developmental Biology, University
of California, Los Angeles, California, 90095, USA
| | - Seanna M. Martin
- Department of Molecular Cell and Developmental Biology, University
of California, Los Angeles, California, 90095, USA
| | - Christian Söllner
- Cell Surface Signalling Laboratory, Wellcome Trust Sanger
Institute, Hinxton, Cambridge CB10 1HH, United Kingdom
| | - Gavin J. Wright
- Cell Surface Signalling Laboratory, Wellcome Trust Sanger
Institute, Hinxton, Cambridge CB10 1HH, United Kingdom
| | - Catherina G. Becker
- Centre for Neuroregeneration, School of Biomedical Sciences,
University of Edinburgh, Summerhall, Edinburgh EH9 1QH, UK
| | - Carlos Portera-Cailliau
- Departments of Neurology and Neurobiology, David Geffen School of
Medicine at UCLA, Los Angeles, California, 90095, USA
| | - Alvaro Sagasti
- Department of Molecular Cell and Developmental Biology, University
of California, Los Angeles, California, 90095, USA
| |
Collapse
|
32
|
Abstract
The nematode Caenorhabditis elegans is emerging as a promising model for studying the molecular control of axon regeneration. A forward genetic screen identified the DLK-1 (dual leucine zipper-bearing kinase 1) MAP (mitogen-activated protein) kinase pathway as a positive regulator of growth cone formation during axon regeneration. Although DLK-1 pathway mutant animals display a dramatic defect in regeneration, their axons have no apparent defects in initial outgrowth. The DLK-1 pathway also plays a role in synaptogenesis, but this role appears to be separate from its function in regeneration. Understanding how the DLK-1 pathway acts in development, plasticity, and regeneration may shed light on the evolution of mechanisms regulating axon regeneration.
Collapse
Affiliation(s)
- Georgeann S O'Brien
- Department of Molecular, Cell and Developmental Biology, University of California-Los Angeles, Los Angeles, CA 90095, USA
| | | |
Collapse
|
33
|
O'Brien GS, Rieger S, Martin SM, Cavanaugh AM, Portera-Cailliau C, Sagasti A. Two-photon axotomy and time-lapse confocal imaging in live zebrafish embryos. J Vis Exp 2009:1129. [PMID: 19229185 PMCID: PMC2726581 DOI: 10.3791/1129] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [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] [Indexed: 10/31/2022] Open
Abstract
Zebrafish have long been utilized to study the cellular and molecular mechanisms of development by time-lapse imaging of the living transparent embryo. Here we describe a method to mount zebrafish embryos for long-term imaging and demonstrate how to automate the capture of time-lapse images using a confocal microscope. We also describe a method to create controlled, precise damage to individual branches of peripheral sensory axons in zebrafish using the focused power of a femtosecond laser mounted on a two-photon microscope. The parameters for successful two-photon axotomy must be optimized for each microscope. We will demonstrate two-photon axotomy on both a custom built two-photon microscope and a Zeiss 510 confocal/two-photon to provide two examples. Zebrafish trigeminal sensory neurons can be visualized in a transgenic line expressing GFP driven by a sensory neuron specific promoter (1). We have adapted this zebrafish trigeminal model to directly observe sensory axon regeneration in living zebrafish embryos. Embryos are anesthetized with tricaine and positioned within a drop of agarose as it solidifies. Immobilized embryos are sealed within an imaging chamber filled with phenylthiourea (PTU) Ringers. We have found that embryos can be continuously imaged in these chambers for 12-48 hours. A single confocal image is then captured to determine the desired site of axotomy. The region of interest is located on the two-photon microscope by imaging the sensory axons under low, non-damaging power. After zooming in on the desired site of axotomy, the power is increased and a single scan of that defined region is sufficient to sever the axon. Multiple location time-lapse imaging is then set up on a confocal microscope to directly observe axonal recovery from injury.
Collapse
Affiliation(s)
- Georgeann S O'Brien
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, USA.
| | | | | | | | | | | |
Collapse
|
34
|
Richler E, Chaumont S, Shigetomi E, Sagasti A, Khakh BS. Tracking transmitter-gated P2X cation channel activation in vitro and in vivo. Nat Methods 2007; 5:87-93. [PMID: 18084300 DOI: 10.1038/nmeth1144] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2007] [Accepted: 11/13/2007] [Indexed: 12/22/2022]
Abstract
We present a noninvasive approach to track activation of ATP-gated P2X receptors and potentially other transmitter-gated cation channels that show calcium fluxes. We genetically engineered rat P2X receptors to carry calcium sensors near the channel pore and tested this as a reporter for P2X(2) receptor opening. The method has several advantages over previous attempts to image P2X channel activation by fluorescence resonance energy transfer (FRET): notably, it reports channel opening rather than a conformation change in the receptor protein. Our FRET-based imaging approach can be used as a general method to track, in real time, the location, regional expression variation, mobility and activation of transmitter-gated P2X channels in living neurons in vitro and in vivo. This approach should help to determine when, where and how different receptors are activated during physiological processes.
Collapse
Affiliation(s)
- Esther Richler
- Department of Physiology, University of California Los Angeles, 10833 LeConte Avenue, Los Angeles, California 90095, USA
| | | | | | | | | |
Collapse
|
35
|
Abstract
Many anatomical and functional features of nervous systems are asymmetric about the left-right axis. These asymmetries can exhibit either random or invariant laterality at the population level. Recent studies in fish and worms provide insight into the developmental mechanisms used to create both types of asymmetry. These studies reveal diverse and molecularly complex strategies for developing asymmetric nervous systems.
Collapse
Affiliation(s)
- Alvaro Sagasti
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, CA 90095, USA.
| |
Collapse
|
36
|
Abstract
The zebrafish is emerging as a system of choice for modeling human disease. In this issue of Cell Metabolism, Mendelsohn et al. (2006) describe a model for Menkes disease, a genetic disorder in copper utilization. Using genetic and chemical screens, the authors highlight the impact of maternal nutrition on embryo development. The work reveals a hierarchy of temporal and dosage-dependent phenotypes for copper nutrition.
Collapse
Affiliation(s)
- Sabeeha S Merchant
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095, USA
| | | |
Collapse
|
37
|
Sagasti A, Guido MR, Raible DW, Schier AF. Repulsive interactions shape the morphologies and functional arrangement of zebrafish peripheral sensory arbors. Curr Biol 2005; 15:804-14. [PMID: 15886097 DOI: 10.1016/j.cub.2005.03.048] [Citation(s) in RCA: 138] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2005] [Revised: 03/25/2005] [Accepted: 03/29/2005] [Indexed: 11/19/2022]
Abstract
BACKGROUND Trigeminal sensory neurons detect thermal and mechanical stimuli in the skin through their elaborately arborized peripheral axons. We investigated the developmental mechanisms that determine the size and shape of individual trigeminal arbors in zebrafish and analyzed how these interactions affect the functional organization of the peripheral sensory system. RESULTS Time-lapse imaging indicated that direct repulsion between growing axons restricts arbor territories. Removal of one trigeminal ganglion allowed axons of the contralateral ganglion to cross the midline, and removal of both resulted in the expansion of spinal cord sensory neuron arbors. Generation of embryos with single, isolated sensory neurons resulted in axon arbors that possessed a vast capacity for growth and expanded to encompass the entire head. Embryos in which arbors were allowed to aberrantly cross the midline were unable to respond in a spatially appropriate way to mechanical stimuli. CONCLUSIONS Direct repulsive interactions between developing trigeminal and spinal cord sensory axon arbors determine sensory neuron organization and control the shapes and sizes of individual arbors. This spatial organization is crucial for sensing the location of objects in the environment. Thus, a combination of undirected growth and mutual repulsion results in the formation of a functionally organized system of peripheral sensory arbors.
Collapse
Affiliation(s)
- Alvaro Sagasti
- Developmental Genetics Program, Skirball Institute of Biomolecular Medicine and Department of Cell Biology, New York University School of Medicine, New York, New York 10016, USA.
| | | | | | | |
Collapse
|
38
|
Tanaka-Hino M, Sagasti A, Hisamoto N, Kawasaki M, Nakano S, Ninomiya-Tsuji J, Bargmann CI, Matsumoto K. SEK-1 MAPKK mediates Ca2+ signaling to determine neuronal asymmetric development in Caenorhabditis elegans. EMBO Rep 2002; 3:56-62. [PMID: 11751572 PMCID: PMC1083920 DOI: 10.1093/embo-reports/kvf001] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The mitogen-activated protein kinase (MAPK) pathway is a highly conserved signaling cascade that converts extracellular signals into various outputs. In Caenorhabditis elegans, asymmetric expression of the candidate odorant receptor STR-2 in either the left or the right of two bilaterally symmetrical olfactory AWC neurons is regulated by axon contact and Ca2+ signaling. We show that the MAPK kinase (MAPKK) SEK-1 is required for asymmetric expression in AWC neurons. Genetic and biochemical analyses reveal that SEK-1 functions in a pathway downstream of UNC-43 and NSY-1, Ca2+/calmodulin-dependent protein kinase II (CaMKII) and MAPK kinase kinase (MAPKKK), respectively. Thus, the NSY-1-SEK-1-MAPK cascade is activated by Ca2+ signaling through CaMKII and establishes asymmetric cell fate decision during neuronal development.
Collapse
Affiliation(s)
- Miho Tanaka-Hino
- Department of Molecular Biology, Graduate School of Science, Nagoya University (and CREST, Japan Science and Technology Corporation), Chikusa-ku, Nagoya 464-8602, Japan
| | | | | | | | | | | | | | | |
Collapse
|
39
|
Sagasti A, Hisamoto N, Hyodo J, Tanaka-Hino M, Matsumoto K, Bargmann CI. The CaMKII UNC-43 activates the MAPKKK NSY-1 to execute a lateral signaling decision required for asymmetric olfactory neuron fates. Cell 2001; 105:221-32. [PMID: 11336672 DOI: 10.1016/s0092-8674(01)00313-0] [Citation(s) in RCA: 162] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A stochastic cell fate decision mediated by axon contact and calcium signaling causes one of the two bilaterally symmetric AWC neurons, either AWCL or AWCR, to express the candidate olfactory receptor str-2. nsy-1 mutants express str-2 in both neurons, disrupting AWC asymmetry. nsy-1 encodes a homolog of the human MAP kinase kinase kinase (MAPKKK) ASK1, an activator of JNK and p38 kinases. Based on genetic epistasis analysis, nsy-1 appears to act downstream of the CaMKII unc-43, and NSY-1 associates with UNC-43, suggesting that UNC-43/CaMKII activates the NSY-1 MAP kinase cassette. Mosaic analysis demonstrates that UNC-43 and NSY-1 act primarily in a cell-autonomous execution step that represses str-2 expression in one AWC cell, downstream of the initial lateral signaling pathway that coordinates the fates of the two cells.
Collapse
Affiliation(s)
- A Sagasti
- Howard Hughes Medical Institute, Programs in Developmental Biology, Neuroscience, and Genetics, Department of Anatomy and Department of, Biochemistry and Biophysics, The University of California, San Francisco, San Francisco, CA 94143, USA
| | | | | | | | | | | |
Collapse
|
40
|
Sagasti A, Schaffner LC, Duffy JE. Effects of periodic hypoxia on mortality, feeding and predation in an estuarine epifaunal community. J Exp Mar Biol Ecol 2001; 258:257-283. [PMID: 11278013 DOI: 10.1016/s0022-0981(01)00220-9] [Citation(s) in RCA: 9] [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: 05/23/2023]
Abstract
The York River Estuary, a tributary of the Chesapeake Bay, USA, experiences periodic low oxygen stress (hypoxia), yet epifaunal species form dense communities there. We studied hypoxia tolerance of common epifaunal species in the York River by exposing sessile and mobile epifauna to high and low oxygen concentrations in laboratory aquaria. Mortality in hypoxia varied among species, ranging from 0% to 100%, with trends of decreased tolerance by mobile species relative to sessile species. While most species tested experienced some mortality after being exposed to hypoxia (at 1 mg O(2)/l or 0.5 mg O(2)/l) for 5 days, many species had a median lethal time (LT(50)) in hypoxia greater than 1 week (3 of 6 species at 1 mg O(2)/l and 6 of 14 species at 0.5 mg O(2)/l), the maximum duration of typical hypoxic episodes in the York River, suggesting that hypoxia may cause little mortality for some species in this system. However, hypoxia had sub-lethal effects on behavior in all species tested. Epifaunal animals responded to hypoxia with behaviors that moved them higher in the water column or by entering resting states until hypoxia passed. Feeding and predation by a variety of taxa (the hydroid Obelia bicuspidata, the mud crab Neopanope sayi, juvenile blue crabs Callinectes sapidus, the flatworm Stylochus ellipticus, and the nudibranch Doridella leucolena) decreased during hypoxia, despite varying mortality responses to low oxygen stress, suggesting that short hypoxic episodes may create predation refuges for prey species. At least one highly tolerant species (O. bicuspidata) showed substantially decreased growth in hypoxia. Although relatively high tolerance of hypoxia by many estuarine epifaunal species limits serious disturbance during brief hypoxic episodes, hypoxia's greatest impact on York River epifaunal communities might be through its indirect effects on behavior and predation.
Collapse
Affiliation(s)
- A Sagasti
- School of Marine Science, Virginia Institute of Marine Science, The College of William and Mary, 23062-1346, Gloucester Point, VA, USA
| | | | | |
Collapse
|
41
|
Abstract
C. elegans detects several odorants with the bilaterally symmetric pair of AWC olfactory neurons. A stochastic, coordinated decision ensures that the candidate odorant receptor gene str-2 is expressed in only one AWC neuron in each animal--either the left or the right neuron, but never both. An interaction between the two AWC neurons generates asymmetric str-2 expression in a process that requires normal axon guidance and probably AWC axon contact. This interaction induces str-2 expression by reducing calcium signaling through a voltage-dependent Ca2+ channel and the CaM kinase II UNC-43. CaMKII activity acts as a switch in the initial decision to express str-2; thus, calcium signals can define distinct cell types during neuronal development. A cGMP signaling pathway that is used in olfaction maintains str-2 expression after the initial decision has been made.
Collapse
Affiliation(s)
- E R Troemel
- Howard Hughes Medical Institute, Department of Anatomy, The University of California, San Francisco 94143-0452, USA
| | | | | |
Collapse
|
42
|
Abstract
The Caenorhabditis elegans AWA, AWB, and AWC olfactory neurons are each required for the recognition of a specific subset of volatile odorants. lim-4 mutants express an AWC reporter gene inappropriately in the AWB olfactory neurons and fail to express an AWB reporter gene. The AWB cells are morphologically transformed toward an AWC fate in lim-4 mutants, adopting cilia and axon morphologies characteristic of AWC. AWB function is also transformed in these mutants: Rather than mediating the repulsive behavioral responses appropriate for AWB, the AWB neurons mediate attractive responses, like AWC. LIM-4 is a predicted LIM homeobox gene that is expressed in AWB and a few other head neurons. Ectopic expression of LIM-4 in the AWC neuron pair is sufficient to force those cells to adopt an AWB fate. The AWA nuclear hormone receptor ODR-7 described previously also represses AWC genes, as well as inducing AWA genes. We propose that the LIM-4 and ODR-7 transcription factors function to diversify C. elegans olfactory neuron identities, driving them from an AWC-like state into alternative fates.
Collapse
Affiliation(s)
- A Sagasti
- Howard Hughes Medical Institute, Department of Anatomy and Department of Biochemistry and Biophysics, University of California, San Francisco, California 94143-0452 USA
| | | | | | | | | |
Collapse
|
43
|
Roayaie K, Crump JG, Sagasti A, Bargmann CI. The G alpha protein ODR-3 mediates olfactory and nociceptive function and controls cilium morphogenesis in C. elegans olfactory neurons. Neuron 1998; 20:55-67. [PMID: 9459442 DOI: 10.1016/s0896-6273(00)80434-1] [Citation(s) in RCA: 273] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The Gi/Go-like G alpha protein ODR-3 is strongly and selectively implicated in the function of C. elegans olfactory and nociceptive neurons. Either loss of odr-3 function or overexpression of odr-3 causes severe olfactory defects, and odr-3 function is essential in the ASH neurons that sense noxious chemical and mechanical stimuli. In the nociceptive neurons, ODR-3 may interact with OSM-9, a channel similar to the mammalian capsaicin receptor implicated in pain sensation; in AWC olfactory neurons, ODR-3 may interact with another signal transduction pathway. ODR-3 exhibits an unexpected ability to regulate morphogenesis of the olfactory cilia. In odr-3 null mutants, the fan-like AWC cilia take on a filamentous morphology like normal AWA cilia, whereas ODR-3 overexpression in AWA transforms its filamentous cilia into a fan-like morphology.
Collapse
Affiliation(s)
- K Roayaie
- Howard Hughes Medical Institute, Department of Anatomy, University of California, San Francisco 94143, USA
| | | | | | | |
Collapse
|
44
|
Becerra SP, Sagasti A, Spinella P, Notario V. Pigment epithelium-derived factor behaves like a noninhibitory serpin. Neurotrophic activity does not require the serpin reactive loop. J Biol Chem 1995; 270:25992-9. [PMID: 7592790 DOI: 10.1074/jbc.270.43.25992] [Citation(s) in RCA: 165] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Pigment epithelium-derived factor (PEDF), a neurite-promoting factor, has an amino acid primary structure that is related to members of the serine protease inhibitor (serpin) family. Controlled proteolysis of native PEDF (50 kDa) with either trypsin, chymotrypsin, elastase, or subtilisin yields in each case one major limited product of 46 kDa as analyzed by SDS-polyacrylamide gel electrophoresis. N-terminal sequence analysis of the isolated 46-kDa products indicates a favored cleavage region located toward the C-terminal end of PEDF. A proteolyzed PEDF protein reaction mixture reveals two overlapping sequences: that of the N terminus of intact PEDF and that of an internal region, consistent with cleavage of PEDF about position 382. These data indicate that PEDF protein has a globular conformation with one protease-sensitive exposed loop that contains the homologous serpin-reactive site. Cleavage within the reactive-site loop of PEDF does not cause a conformational change in the molecules (the stressed (S)-->relaxed (R) transition) and results in heat denaturation identical to its native counterpart. This lack of conformational change is also seen upon cleavage within the reactive-site loop of the noninhibitory serpin ovalbumin. Furthermore, the PEDF neurite-promoting function is not lost with cleavage of the exposed loop. Recombinant PEDF polypeptide fragments with larger truncations from the C-terminal end show neurotrophic activity. Our results clearly indicate that integrity of the PEDF homologous serpin reactive center is dispensable for neurotrophic activity. Thus, the PEDF induction of neurites must be mediated by a mechanism other than serine protease inhibition. Altogether our data indicate that PEDF belongs to the subgroup of noninhibitory serpins and that its N-terminal region confers a neurite-promoting activity to the protein. The neurotrophic active site of PEDF is separated from the serpin reactive-site loop, not only in the primary structure, but also in the folded protein structure.
Collapse
Affiliation(s)
- S P Becerra
- Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | | | | | | |
Collapse
|