Nucleation and Transport Organize Microtubules in Metaphase Spindles

Brugués, Jan; Nuzzo, Valeria; Mazur, Eric; Needleman, Daniel

doi:10.1016/j.cell.2012.03.027

Cited by 165 publications

(214 citation statements)

References 55 publications

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“…By comparing the two waves, information about the polarity of MTs could be obtained, and irradiating different regions of the spindle showed that MTs were longer near the center of the spindle and shorter toward the poles. Interestingly, inhibition of poleward MT flux homogenized spindle MT lengths, supporting a model in which spindle architecture depends on both the position of MT nucleation near the center of the spindle and poleward MT transport (Brugues et al, 2012).…”

mentioning

confidence: 77%

“…Perhaps more interestingly, tubulin lifetime measurements did not vary across different regions of the spindle, suggesting that despite specific localization of factors that alter MT dynamics within the spindle, overall MT stability is uniform. Further support for a model of spindle organization with homogenous MT stability in all regions stems from using a femtosecond laser ablation technique to cut a subset of MTs within a metaphase Xenopus egg extract spindle (Brugues et al, 2012;Fig. 3.3D).…”

mentioning

confidence: 99%

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Interplay Between Spindle Architecture and Function

Helmke

Heald

Wilbur

2013

International Review of Cell and Molecular Biology

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mentioning

confidence: 77%

mentioning

confidence: 99%

Interplay Between Spindle Architecture and Function

Helmke

Heald

Wilbur

2013

International Review of Cell and Molecular Biology

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“…4b), indicating that the majority of minus-ends of microtubules in C. elegans spindles are located at the centrosomes, whereas plus-ends grow towards the chromosomes. We challenged this finding by performing laser microsurgery to ablate microtubules within the spindle and so measure their polarity by generating new microtubule plus-and minus-ends 24 . Microsurgery resulted in the formation of a single wave of depolymerization of the newly created microtubule plus-ends towards the centrosome (Supplementary Movie 4).…”

Section: Resultsmentioning

confidence: 99%

“…While light microscopy provides a dynamic picture of the spindle 15,[22][23][24] , it cannot resolve individual microtubules. Electron microscopy overcomes this limitation though, until now, little quantitative data on the fine structure of mitotic spindles has been published.…”

mentioning

confidence: 99%

C. Elegans Chromosomes Connect to Centrosomes by Anchoring into the Spindle Network

Redemann

Baumgart

Lindow

et al. 2018

Biophysical Journal

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The mitotic spindle ensures the faithful segregation of chromosomes. Here we combine the first large-scale serial electron tomography of whole mitotic spindles in early C. elegans embryos with live-cell imaging to reconstruct all microtubules in 3D and identify their plus-and minus-ends. We classify them as kinetochore (KMTs), spindle (SMTs) or astral microtubules (AMTs) according to their positions, and quantify distinct properties of each class. While our light microscopy and mutant studies show that microtubules are nucleated from the centrosomes, we find only a few KMTs directly connected to the centrosomes. Indeed, by quantitatively analysing several models of microtubule growth, we conclude that minus-ends of KMTs have selectively detached and depolymerized from the centrosome. In toto, our results show that the connection between centrosomes and chromosomes is mediated by an anchoring into the entire spindle network and that any direct connections through KMTs are few and likely very transient.

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“…The spatial distribution of microtubule nucleation is key for understanding size and architecture of large spindles. This is because microtubules in these spindles are short and turnover rapidly (3,10,11). The mechanisms underlying the spatial regulation of microtubule nucleation, however, are still unclear (12, 13).…”

Section: Main Textmentioning

confidence: 99%

Autocatalytic microtubule nucleation determines the size and mass of spindles

Decker¹,

Oriola²,

Dalton³

et al. 2017

Preprint

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Regulation of size and growth is a fundamental problem in biology. A prominent example is the formation of the mitotic spindle, where protein concentration gradients around chromosomes are thought to regulate spindle growth by controlling microtubule nucleation (1,2). Previous evidence suggests that microtubules nucleate throughout the spindle structure (3-5). However, the mechanisms underlying microtubule nucleation and its spatial regulation are still unclear. Here, we developed an assay based on laser ablation to directly probe microtubule nucleation events in Xenopus laevis egg extracts. Combining this method with theory and quantitative microscopy, we show that the size of a spindle is controlled by autocatalytic growth of microtubules, driven by microtubule-stimulated microtubule nucleation. The autocatalytic activity of this nucleation system is spatially regulated by the limiting amounts of active microtubule nucleators, which decrease with distance from the chromosomes. Thus, the size of spindles is determined by the distance where one microtubule nucleates on average less than one new microtubule. This mechanism . CC-BY-NC 4.0 International license not peer-reviewed) is the author/funder. It is made available under a The copyright holder for this preprint (which was . http://dx.doi.org/10.1101/174078 doi: bioRxiv preprint first posted online Aug. 9, 2017; provides an upper limit to spindle size even when resources are not limiting and may have implications for spindle scaling during development (6,7). Main textA general class of problems in biology is related to the emergence of size and shape in cells and tissues. Reaction diffusion mechanisms have been broadly successful in explaining spatial patterns in developmental biology as well as some instances of intracellular structures (8,9). The mitotic spindle, a macromolecular machine responsible for segregating chromosomes during cell division, is thought to be a classic example of such reaction diffusion processes. A diffusible gradient of the small GTPase Ran emanating from chromosomes has been shown to trigger a cascade of events that result in the nucleation of microtubules, the main building blocks of the spindle (1, 2). The spatial distribution of microtubule nucleation is key for understanding size and architecture of large spindles. This is because microtubules in these spindles are short and turnover rapidly (3,10,11). The mechanisms underlying the spatial regulation of microtubule nucleation, however, are still unclear (12, 13).One possibility is that the interplay between Ran-mediated nucleation and microtubule turnover governs spindle assembly (1, 2). However, the role of the Ran gradient in determining spindle size is still controversial. For instance, in cell culture systems, the length scale of the Ran gradient does not correlate with spindle size (5).A second possibility is that autocatalytic growth accounts for spindle assembly via microtubule-stimulated microtubule nucleation (4,(14)(15)(16). However, autocatalytic . CC-BY-N...

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Nucleation and Transport Organize Microtubules in Metaphase Spindles

Cited by 165 publications

References 55 publications

Interplay Between Spindle Architecture and Function

Interplay Between Spindle Architecture and Function

C. Elegans Chromosomes Connect to Centrosomes by Anchoring into the Spindle Network

Autocatalytic microtubule nucleation determines the size and mass of spindles

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