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Abstract
The field of microfluidics allows for the precise spatial manipulation of small amounts of fluids. Within microstructures, laminar flow of fluids can be exploited to control the diffusion of small molecules, creating desired microenvironments for cells. Cellular neuroscience has benefited greatly from devices designed to fluidically isolate cell bodies and axons. Microfluidic devices specialized for neuron compartmentalization are made of polydimethylsiloxane (PDMS) which is gas permeable, is compatible with fluorescence microscopy, and has low cost. These devices are commonly used to study signals initiated exclusively on axons, somatodendritic compartments, or even single synapses. We have also found that microfluidic devices allow for rapid, reproducible interrogation of axon degeneration. Here, we describe the methodology for assessing axonal degeneration in microfluidic devices. We describe several use cases, including enucleation (removal of cell bodies) and trophic deprivation to investigate axon degeneration in pathological and developmental scenarios, respectively.
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Affiliation(s)
- Yu Yong
- Department of Biology, University of Virginia, Charlottesville, VA, USA
| | - Christopher Hughes
- Department of Physics and Astronomy, James Madison University, Harrisonburg, VA, USA
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Gamage KK, Cheng I, Park RE, Karim MS, Edamura K, Hughes C, Spano AJ, Erisir A, Deppmann CD. Death Receptor 6 Promotes Wallerian Degeneration in Peripheral Axons. Curr Biol 2017; 27:890-896. [PMID: 28285993 DOI: 10.1016/j.cub.2017.01.062] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [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: 10/14/2016] [Revised: 12/19/2016] [Accepted: 01/30/2017] [Indexed: 11/17/2022]
Abstract
Axon degeneration during development is required to sculpt a functional nervous system and is also a hallmark of pathological insult, such as injury [1, 2]. Despite similar morphological characteristics, very little overlap in molecular mechanisms has been reported between pathological and developmental degeneration [3-5]. In the peripheral nervous system (PNS), developmental axon pruning relies on receptor-mediated extrinsic degeneration mechanisms to determine which axons are maintained or degenerated [5-7]. Receptors have not been implicated in Wallerian axon degeneration; instead, axon autonomous, intrinsic mechanisms are thought to be the primary driver for this type of axon disintegration [8-10]. Here we survey the role of neuronally expressed, paralogous tumor necrosis factor receptor super family (TNFRSF) members in Wallerian degeneration. We find that an orphan receptor, death receptor 6 (DR6), is required to drive axon degeneration after axotomy in sympathetic and sensory neurons cultured in microfluidic devices. We sought to validate these in vitro findings in vivo using a transected sciatic nerve model. Consistent with the in vitro findings, DR6-/- animals displayed preserved axons up to 4 weeks after injury. In contrast to phenotypes observed in Wlds and Sarm1-/- mice, preserved axons in DR6-/- animals display profound myelin remodeling. This indicates that deterioration of axons and myelin after axotomy are mechanistically distinct processes. Finally, we find that JNK signaling after injury requires DR6, suggesting a link between this novel extrinsic pathway and the axon autonomous, intrinsic pathways that have become established for Wallerian degeneration.
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Affiliation(s)
- Kanchana K Gamage
- Department of Biology, University of Virginia, Charlottesville, VA 22903, USA
| | - Irene Cheng
- Department of Biology, University of Virginia, Charlottesville, VA 22903, USA; Neuroscience Graduate Program, University of Virginia, Charlottesville, VA 22903, USA
| | - Rachel E Park
- Department of Biology, University of Virginia, Charlottesville, VA 22903, USA
| | - Mardeen S Karim
- Department of Biology, University of Virginia, Charlottesville, VA 22903, USA
| | - Kazusa Edamura
- Department of Biology, University of Virginia, Charlottesville, VA 22903, USA
| | - Christopher Hughes
- Department of Physics and Astronomy, James Madison University, Harrisonburg, VA 22807, USA
| | - Anthony J Spano
- Department of Biology, University of Virginia, Charlottesville, VA 22903, USA
| | - Alev Erisir
- Department of Psychology, University of Virginia, Charlottesville, VA 22903, USA
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