Dynein and dynactin move long-range but are delivered separately to the axon tip

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Abstract

Axonal transport is essential for neuronal survival. This is driven by microtubule motors including dynein, which transports cargo from the axon tip back to the cell body. This function requires its cofactor dynactin and regulators LIS1 and NDEL1. Due to difficulties imaging dynein at a single-molecule level, it is unclear how this motor and its regulators coordinate transport along the length of the axon. Here, we use a neuron-inducible human stem cell line (NGN2-OPTi-OX) to endogenously tag dynein components and visualize them at a near-single molecule regime. In the retrograde direction, we find that dynein and dynactin can move the entire length of the axon (>500 µm). Furthermore, LIS1 and NDEL1 also undergo long-distance movement, despite being mainly implicated with the initiation of dynein transport. Intriguingly, in the anterograde direction, dynein/LIS1 moves faster than dynactin/NDEL1, consistent with transport on different cargos. Therefore, neurons ensure efficient transport by holding dynein/dynactin on cargos over long distances but keeping them separate until required.

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  1. Note: This rebuttal was posted by the corresponding author to Review Commons. Content has not been altered except for formatting.

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    Reply to the reviewers

    Reviewer #1:

    1. If doable, image dynein and dynactin simultaneously in the Halo-DYNC1H1/DCTN4-SNAP iNeurons. Co-movement of dynein and dynactin towards the somatodendritic compartment and their separate movement in the anterograde direction along the axon would provide the most convincing evidence for the key claims of the manuscript.

    Please see the planned revision section for our response

    Reviewer #2:

    Major comment (requires additional experimentation)

    1. While the data presented do certainly suggest that dynein and Lis1 are transported anterogradely on separate vesicular cargoes from dynactin and Ndel1, the study would be much stronger if supported by dual …
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    Referee #3

    Evidence, reproducibility and clarity

    Fellows and coauthors present a signle-molecule study toward dynein regulation in axons. They observe that dynein in vivo makes very long runs and that regulators LIS1 and NDEL1 cotransport with dynein all the (retrograde way). Remarkably, different components of the dynein complex appear to be transported in different ways/velocities in the antorograde direction. Overall experiments are well conducted, I only have a couple of important questions regarding data analysis. Some aspects should be explained better, more steps should be shown and here and there I think the authors could, with minimal effort, obtain much more out of their …

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    Referee #2

    Evidence, reproducibility and clarity

    Summary - The authors use a CRISPR knock-in gene editing strategy to label endogenous dynein, dynactin (p62 or Arp11) and dynein regulators (Ndel1 and Lis1) with Halo or SNAP tags. They do this in human iPSC and ESC cell lines engineered to express doxycycline-inducible NGN2 cloned into a "safe harbor" site of the genome. They induce the cells to differentiate into iNeurons using doxycycline and image the tagged proteins in axons with single molecule sensitivity using HILO illumination. The paper is clearly written, the description of the methods is thorough, and the data and figures (including the videos) are of good quality. The …

  4. Note: This preprint has been reviewed by subject experts for Review Commons. Content has not been altered except for formatting.

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    Referee #1

    Evidence, reproducibility and clarity

    To image dynein in the axon at a single-molecule level, Fellows et al. used neuron-inducible human stem cell lines to Halo/SNAP tag endogenous dynein components by gene editing, and visualized fluorescently labeled protein molecules in differentiated neurons in microfluidic chambers by HILO microscopy-based live imaging. Using those cutting edge technologies, the authors demonstrate that in the axon, not only dynein and dynactin but also the dynein regulators LIS1 and NDEL1 can move long distance retrogradely towards the somatodendritic compartment. They also show that dynein /LIS1 move faster than dynactin/NDEL1 in the anterograde …

  5. This Zenodo record is a permanently preserved version of a PREreview. You can view the complete PREreview at https://prereview.org/reviews/8362691.

    This review reflects comments and contributions from Kamaldeep Singh, Prithviraj Rajebhosale, Luciana Gallo, Ryan Cubero & Femi Arogundade. Review synthesized by Kamaldeep Singh.

    In this study, Fellows et al. investigated the motility of endogenously-tagged dynein motors and its regulators along the length of the axons using live imaging of neuron-inducible human-stem cell lines (iNeurons) as a model system. Using highly inclined and laminated optical sheet (HILO) imaging of iNeurons, they show that dynein and dynactin are transported at different speeds to the distal tip of the axon. Further, use of SNAP and Halo-tag conjugated with highly stable fluorophores also allowed them to show …