Augmin-dependent microtubule self-organization drives kinetochore fiber maturation in mammals

Almeida, Ana C; Soares-de-Oliveira, Joana; Drpic, Danica; Cheeseman, Liam P.; Damas, Joana; Lewin, Harris A.; Larkin, Denis M.; Aguiar, Paulo; Pereira, António J.; Maiato, Hélder

doi:10.1016/j.celrep.2022.110610

Cited by 15 publications

(26 citation statements)

References 101 publications

(136 reference statements)

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“…In addition to spindle architecture, compromised microtubule nucleation following augmin depletion also affected spindle dynamics, as poleward flux in U2OS cells stably expressing CENP-A-GFP, mCherry-tubulin and photoactivatable-GFP-α-tubulin was significantly reduced (Supplementary Fig. S3L-M), in agreement with findings in Indian Muntjac cells (Almeida et al, 2022). Recent speckle microscopy experiments in RPE1 cells, which were able to separate the effect of augmin on poleward flux of bridging and k-fibers, revealed that both k-fibers and the remaining bridging fibers were significantly slowed down (Risteski et al, 2021 Preprint ).…”

Section: Resultssupporting

confidence: 83%

“…Augmin depletion has previously been linked to higher incidence of segregation errors (Wu et al, 2008) and the appearance of lagging chromosomes (Almeida et al, 2022;Viais et al, 2021), which were connected to impaired brain development in a recent study (Viais et al, 2021).…”

Section: Introductionmentioning

confidence: 87%

“…Augmin-nucleated microtubules grow at an angle of 0-30° relative to the pre-existing microtubule (Kamasaki et al, 2013; Petry et al, 2013; Verma and Maresca, 2019) and show a directional bias towards kinetochores, resulting in the preserved polarity of the spindle once the initial kinetochore-microtubule attachments form (David et al, 2019; Kamasaki et al, 2013). Depletion of augmin complex in different cell types results in impairment of microtubule bundles within the spindle accompanied by the formation of long, curved bundles on the spindle periphery, loss of spindle bipolarity, shorter interkinetochore distance, chromosome misalignment, mitotic delays, and a higher incidence of aneuploidy and cytokinesis failure (Almeida et al, 2022; Hayward et al, 2014; Uehara and Goshima, 2010; Uehara et al, 2009; Wu et al, 2008; Zhu et al, 2008). Of the eight subunits in the complex, the two directly interacting subunits HAUS6 (hDgt6/FAM29A) and HAUS8 (hDgt4/Hice1) have been extensively studied because of their ability to interact with a γ-TuRC adapter protein NEDD1 and pre-existing microtubules, respectively (Song et al, 2018; Uehara et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

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Augmin prevents merotelic attachments by promoting proper arrangement of bridging and kinetochore fibers

Manenica

Koprivec

Štimac

et al. 2020

Preprint

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The mitotic spindle functions as a molecular micromachine that evenly distributes chromosomes into two daughter cells during cell division. A major mechanical element of the spindle are kinetochore fibers attached to sister kinetochores on each chromosome and laterally linked by a bundle of antiparallel microtubules called the bridging fiber. Spindle microtubules are mainly nucleated at the centrosome and on the lateral surface of existing microtubules by the augmin complex. However, it is unknown how the augmin-mediated nucleation affects functionally distinct microtubule bundles and thus the architecture and forces within the spindle. Here we show, by using siRNA depletion and CRISPR knock-out of the augmin complex subunits HAUS6 and HAUS8 in human cells, that augmin is a major contributor to the nucleation of bridging microtubules. Augmin depletion resulted in a ∼70% reduction of the microtubule number in bridging fibers and ∼40% in kinetochore fibers, suggesting that the bridging microtubules are largely nucleated at the surface of present microtubules. In augmin-depleted cells, the interkinetochore distance decreases preferentially for kinetochores that lack a bridging fiber, independently of the thickness of their k-fibers, indicating that augmin affects forces on kinetochores largely via bridging fibers. Without augmin the number of bridging fibers decreases, with the remaining ones mostly confined to the spindle periphery with an increased overlap length. The reduced number of microtubules also results in a slower poleward flux. Our results demonstrate a critical role of augmin in the formation of bridging microtubules and proper architecture of the metaphase spindle, suggesting a model where sliding of augmin-nucleated bridging microtubules promotes poleward flux of k-fibers and thus tension on kinetochores.

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Section: Resultssupporting

confidence: 83%

Section: Introductionmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

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Augmin prevents merotelic attachments by promoting proper arrangement of bridging and kinetochore fibers

Manenica

Koprivec

Štimac

et al. 2020

Preprint

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“…These non-KMTs could be nucleated by a variety of mechanisms in the spindle bulk such as by the Augmin complex ( Goshima et al, 2008 ; David et al, 2019 ). Alternatively, Augmin nucleated non-KMTs may increase the local density of aligned MTs around the k-Fiber and therefore reinforce the existing KMT trajectories ( Almeida et al, 2022 ). The metaphase kinetochore nucleation model predicts that the minus end speed monotonically increases with distance away from the pole along streamlines ( Figure 6E , see supplement).…”

Section: Resultsmentioning

confidence: 99%

Self-organization of kinetochore-fibers in human mitotic spindles

Conway

Kiewisz

Fabig

et al. 2022

eLife

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During eukaryotic cell division, chromosomes are linked to microtubules (MTs) in the spindle by a macromolecular complex called the kinetochore. The bound kinetochore microtubules (KMTs) are crucial to ensuring accurate chromosome segregation. Recent reconstructions by electron tomography (Kiewisz et al. 2021) captured the positions and configurations of every MT in human mitotic spindles, revealing that roughly half the KMTs in these spindles do not reach the pole. Here, we investigate the processes that give rise to this distribution of KMTs using a combination of analysis of large-scale electron tomography, photoconversion experiments, quantitative polarized light microscopy, and biophysical modeling. Our results indicate that in metaphase, KMTs grow away from the kinetochores along well-defined trajectories, with the speed of the KMT minus ends continually decreasing as the minus ends approach the pole, implying that longer KMTs grow more slowly than shorter KMTs. The locations of KMT minus ends, and the turnover and movements of tubulin in KMTs, are consistent with models in which KMTs predominately nucleate de novo at kinetochores in metaphase and are inconsistent with substantial numbers of non-KMTs being recruited to the kinetochore in metaphase. Taken together, this work leads to a mathematical model of the self-organization of kinetochore-fibers in human mitotic spindles.

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“…Yet, without dynein, the formation of k-fibers is not disrupted [92]. Amplification of short and sorted kinetochore-nucleated MTs could be aided by the augmin complex [93] that contributes to kinetochore MT growth even in the absence of pre-existing centrosomal MTs [94].…”

Section: Getting To the Equator-congression From The Spindle Pole To ...mentioning

confidence: 99%

Polar Chromosomes—Challenges of a Risky Path

Vukušić

Tolić

2022

Cells

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The process of chromosome congression and alignment is at the core of mitotic fidelity. In this review, we discuss distinct spatial routes that the chromosomes take to align during prometaphase, which are characterized by distinct biomolecular requirements. Peripheral polar chromosomes are an intriguing case as their alignment depends on the activity of kinetochore motors, polar ejection forces, and a transition from lateral to end-on attachments to microtubules, all of which can result in the delayed alignment of these chromosomes. Due to their undesirable position close to and often behind the spindle pole, these chromosomes may be particularly prone to the formation of erroneous kinetochore-microtubule interactions, such as merotelic attachments. To prevent such errors, the cell employs intricate mechanisms to preposition the spindle poles with respect to chromosomes, ensure the formation of end-on attachments in restricted spindle regions, repair faulty attachments by error correction mechanisms, and delay segregation by the spindle assembly checkpoint. Despite this protective machinery, there are several ways in which polar chromosomes can fail in alignment, mis-segregate, and lead to aneuploidy. In agreement with this, polar chromosomes are present in certain tumors and may even be involved in the process of tumorigenesis.

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Augmin-dependent microtubule self-organization drives kinetochore fiber maturation in mammals

Cited by 15 publications

References 101 publications

Augmin prevents merotelic attachments by promoting proper arrangement of bridging and kinetochore fibers

Augmin prevents merotelic attachments by promoting proper arrangement of bridging and kinetochore fibers

Self-organization of kinetochore-fibers in human mitotic spindles

Polar Chromosomes—Challenges of a Risky Path

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