Menu

Close

Optogenetic reconstitution reveals that Dynein-Dynactin-NuMA clusters generate cortical spindle-pulling forces as a multi-arm ensemble

Masako Okumura, Toyoaki Natsume, Masato T Kanemaki, Tomomi Kiyomitsu

Preprint posted on March 06, 2018 https://www.biorxiv.org/content/early/2018/03/06/277202

NuMA in the spotlight: Optogenetic activation shows that Dynein-Dynactin-NuMA clusters take centre stage during spindle positioning

Selected by Ben Craske, Thibault Legal and Toni McHugh

Categories: cell biology

Context:

Mitotic cortical force machinery assembles on the plasma membrane and provides pulling forces on astral microtubules (MTs) that are important for the correct positioning of the spindle.  Correct spindle positioning is important for both symmetric and asymmetric divisions, determining both cell size and fate following segregation of genetic material. In human cells, this machinery consists of the cortically anchored complex of Nuclear Mitotic Apparatus protein (NuMA), LGN and G alpha i (NuMA-LGN-Gαi), with cytoplasmic dynein and dynactin. The complex generates pulling forces on astral MTs through dynein’s minus-end directed motility and/or the control of MT dynamics. The authors use a light-induced membrane tethering system (iLID) to assess the mechanism by which NuMA contributes to cortical force generation (Figure 1A).

Key Findings:

Using the iLID system, the authors show that spindles displace towards light-activated regions of the cortex upon NuMA, Dynein Heavy Chain (DHC) and p150 recruitment, and are able to show that repositioning of the light-induced cortical NuMA allows rotational reorientation of spindles. Although dynein-dynactin is required for cortical pulling, it is not sufficient for spindle displacement in the absence of NuMA. It contains a 200nm long central coiled-coil domain that is necessary for spindle pulling, and two additional microtubule-binding domains in the C-terminus. Together with dynein-dynactin, these regions allow NuMA clusters to efficiently capture and maintain associations with the plus-tips of astral microtubules in order to generate cortical pulling forces that are required for spindle positioning.

Figure 1A: Diagram summarising cortical complexes in the indicated conditions (from Okumura et al. 2018, reproduced with permission from the authors)

 

Why we chose this preprint:

We were drawn to this preprint thanks to the authors’ elegant use of a light induced system to reconstitute spindle pulling forces at the cortex. This preprint further highlights the power of using optogenetic tools to investigate protein function with precise spatial and temporal control, with the potential for much wider applications within other areas of cell biology. Here, by targeting the dynein-dynactin-NuMA (DDN) complex to the cortex, they further elucidate the underlying mechanisms controlling spindle positioning which is a topic of great interest to our lab.

Open Questions:

This paper makes a significant step in dissecting the mechanism of cortical pulling by highlighting the requirement for both active dynein and additional microtubule-binding domains in NuMA to generate cortical forces. The authors note that NuMA tends to form distinct punctae on the membrane and hypothesize that it may be forming a higher-order complex in order to generate force. What might this structure look like? Finally, the authors show that slow spindle displacement can even be seen when microtubules are taxol-stabilized, removing microtubule depolymerisation at the cortex. In this case, what role are microtubule dynamics and pushing on the cortex playing during the process of spindle centering?

 

Posted on: 10th May 2018

Read preprint (No Ratings Yet)




  • Have your say

    Your email address will not be published. Required fields are marked *

    Sign up to customise the site to your preferences and to receive alerts

    Register here

    Also in the cell biology category:

    The cytoskeleton as a smart composite material: A unified pathway linking microtubules, myosin-II filaments and integrin adhesions

    Nisha Mohd Rafiq, Yukako Nishimura, Sergey V. Plotnikov, et al.



    Selected by Coert Margadant

    Quantitative, real-time, single cell analysis in tissue reveals expression dynamics of neurogenesis

    Cerys S Manning, Veronica Biga, James Boyd, et al.



    Selected by Teresa Rayon

    Profiling the surface proteome identifies actionable biology for TSC1 mutant cells beyond mTORC1 signaling

    Junnian Wei, Kevin K. Leung, Charles Truillet, et al.



    Selected by Rob Hynds

    1

    Optogenetic dissection of mitotic spindle positioning in vivo

    Lars-Eric Fielmich, Ruben Schmidt, Daniel J Dickinson, et al.



    Selected by Angika Basant

    1

    Excitable RhoA dynamics drive pulsed contractions in the early C. elegans embryo.

    Jonathan B Michaux, Francois B Robin, William M McFadden, et al.



    Selected by Sundar Naganathan

    Moving beyond P values: Everyday data analysis with estimation plots

    Joses Ho, Tayfun Tumkaya, Sameer Aryal, et al.



    Selected by Gautam Dey

    1

    A limited number of double-strand DNA breaks are sufficient to delay cell cycle progression.

    Jeroen van den Berg, Anna G. Manjon, Karoline Kielbassa, et al.



    Selected by Leighton Daigh

    Optogenetic manipulation of medullary neurons in the locust optic lobe

    Hongxia Wang, Richard B. Dewell, Markus U. Ehrengruber, et al.



    Selected by Ana Patricia Ramos

    JNK-mediated spindle reorientation in stem cells promotes dysplasia in the aging intestine

    Daniel Hu, Heinrich Jasper



    Selected by Maiko Kitaoka

    ER-to-Golgi trafficking of procollagen in the absence of large carriers.

    Janine McCaughey, Nicola Stevenson, Stephen Cross, et al.



    Selected by Gautam Dey

    1

    Template switching causes artificial junction formation and false identification of circular RNAs

    Chong Tang, Tian Yu, Yeming Xie, et al.



    Selected by Fabio Liberante

    Mechanosensitive binding of p120-Catenin at cell junctions regulates E-Cadherin turnover and epithelial viscoelasticity

    K. Venkatesan Iyer, Romina Piscitello-Gómez, Frank Jülicher, et al.



    Selected by Ivana Viktorinová

    Targeting light-gated chloride channels to neuronal somatodendritic domain reduces their excitatory effect in the axon

    Jessica Messier, Hongmei Chen, Zhao-Lin Cai, et al.

    AND

    High-efficiency optogenetic silencing with soma-targeted anion-conducting channelrhodopsins

    Mathias Mahn, Lihi Gibor, Katayun Cohen-Kashi Malina, et al.



    Selected by Mahesh Karnani

    2

    EFFECTORS OF THE SPINDLE ASSEMBLY CHECKPOINT BUT NOT THE MITOTIC EXIT NETWORK ARE CONFINED WITHIN THE NUCLEUS OF SACCHAROMYCES CEREVISIAE

    Lydia R Heasley, Jennifer G DeLuca, Steven M Markus



    Selected by Hiral Shah

    An atlas of the aging lung mapped by single cell transcriptomics and deep tissue proteomics

    Ilias Angelidis, Lukas M Simon, Isis E Fernandez, et al.



    Selected by Rob Hynds

    1

    Peculiar features of the plastids of the colourless alga Euglena longa and photosynthetic euglenophytes unveiled by transcriptome analyses

    Kristina Zahonova, Zoltan Fussy, Erik Bircak, et al.



    Selected by Ellis O'Neill

    1

    Close