Live imaging reveals the cellular events downstream of SARM1 activation

  1. Kwang Woo Ko
  2. Laura Devault
  3. Yo Sasaki
  4. Jeffrey Milbrandt  Is a corresponding author
  5. Aaron DiAntonio  Is a corresponding author
  1. Washington University School of Medicine, United States

Abstract

SARM1 is an inducible NAD+ hydrolase that triggers axon loss and neuronal cell death in the injured and diseased nervous system. While SARM1 activation and enzyme function are well defined, the cellular events downstream of SARM1 activity but prior to axonal demise are much less well understood. Defects in calcium, mitochondria, ATP, and membrane homeostasis occur in injured axons, but the relationships among these events have been difficult to disentangle because prior studies analyzed large collections of axons in which cellular events occur asynchronously. Here we used live imaging of mouse sensory neurons with single axon resolution to investigate the cellular events downstream of SARM1 activity. Our studies support a model in which SARM1 NADase activity leads to an ordered sequence of events from loss of cellular ATP, to defects in mitochondrial movement and depolarization, followed by calcium influx, externalization of phosphatidylserine, and loss of membrane permeability prior to catastrophic axonal self-destruction.

Data availability

All data generated or analyzed during this study are included in the manuscript and supporting files.

Article and author information

Author details

  1. Kwang Woo Ko

    Washington University School of Medicine, St Louis, United States
    Competing interests
    The authors declare that no competing interests exist.
  2. Laura Devault

    Washington University School of Medicine, St Louis, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Yo Sasaki

    Washington University School of Medicine, St Louis, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-0024-0031
  4. Jeffrey Milbrandt

    Washington University School of Medicine, St Louis, United States
    For correspondence
    jmilbrandt@wustl.edu
    Competing interests
    The authors declare that no competing interests exist.
  5. Aaron DiAntonio

    Washington University School of Medicine, St Louis, United States
    For correspondence
    diantonio@wustl.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-7262-0968

Funding

National Institutes of Health (R01CA219866)

  • Jeffrey Milbrandt
  • Aaron DiAntonio

National Institutes of Health (RO1NS087632)

  • Jeffrey Milbrandt
  • Aaron DiAntonio

National Institutes of Health (RF1-AG013730)

  • Jeffrey Milbrandt

National Institutes of Health (F32NS117784)

  • Laura Devault

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Graeme W Davis, University of California, San Francisco, United States

Version history

  1. Received: June 10, 2021
  2. Preprint posted: June 15, 2021 (view preprint)
  3. Accepted: November 12, 2021
  4. Accepted Manuscript published: November 15, 2021 (version 1)
  5. Version of Record published: November 24, 2021 (version 2)

Copyright

© 2021, Ko et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

Metrics

  • 2,211
    views
  • 440
    downloads
  • 40
    citations

Views, downloads and citations are aggregated across all versions of this paper published by eLife.

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Open citations (links to open the citations from this article in various online reference manager services)

Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)

  1. Kwang Woo Ko
  2. Laura Devault
  3. Yo Sasaki
  4. Jeffrey Milbrandt
  5. Aaron DiAntonio
(2021)
Live imaging reveals the cellular events downstream of SARM1 activation
eLife 10:e71148.
https://doi.org/10.7554/eLife.71148

Share this article

https://doi.org/10.7554/eLife.71148

Further reading

    1. Neuroscience
    Alexandra L Jellinger, Rebecca L Suthard ... Steve Ramirez
    Research Article

    Negative memories engage a brain and body-wide stress response in humans that can alter cognition and behavior. Prolonged stress responses induce maladaptive cellular, circuit, and systems-level changes that can lead to pathological brain states and corresponding disorders in which mood and memory are affected. However, it is unclear if repeated activation of cells processing negative memories induces similar phenotypes in mice. In this study, we used an activity-dependent tagging method to access neuronal ensembles and assess their molecular characteristics. Sequencing memory engrams in mice revealed that positive (male-to-female exposure) and negative (foot shock) cells upregulated genes linked to anti- and pro-inflammatory responses, respectively. To investigate the impact of persistent activation of negative engrams, we chemogenetically activated them in the ventral hippocampus over 3 months and conducted anxiety and memory-related tests. Negative engram activation increased anxiety behaviors in both 6- and 14-month-old mice, reduced spatial working memory in older mice, impaired fear extinction in younger mice, and heightened fear generalization in both age groups. Immunohistochemistry revealed changes in microglial and astrocytic structure and number in the hippocampus. In summary, repeated activation of negative memories induces lasting cellular and behavioral abnormalities in mice, offering insights into the negative effects of chronic negative thinking-like behaviors on human health.

    1. Neuroscience
    Alexandra H Leighton, Juliette E Cheyne, Christian Lohmann
    Research Article

    Synaptic inputs to cortical neurons are highly structured in adult sensory systems, such that neighboring synapses along dendrites are activated by similar stimuli. This organization of synaptic inputs, called synaptic clustering, is required for high-fidelity signal processing, and clustered synapses can already be observed before eye opening. However, how clustered inputs emerge during development is unknown. Here, we employed concurrent in vivo whole-cell patch-clamp and dendritic calcium imaging to map spontaneous synaptic inputs to dendrites of layer 2/3 neurons in the mouse primary visual cortex during the second postnatal week until eye opening. We found that the number of functional synapses and the frequency of transmission events increase several fold during this developmental period. At the beginning of the second postnatal week, synapses assemble specifically in confined dendritic segments, whereas other segments are devoid of synapses. By the end of the second postnatal week, just before eye opening, dendrites are almost entirely covered by domains of co-active synapses. Finally, co-activity with their neighbor synapses correlates with synaptic stabilization and potentiation. Thus, clustered synapses form in distinct functional domains presumably to equip dendrites with computational modules for high-capacity sensory processing when the eyes open.